Category: crop

Interlacing: lessons for seed mixes today?

“… an allowance is made for interlacing.”

Stebler and Schröter’s 1889 handbook on grass and legume species and mixtures. Their method of estimating seed rate for each species in a mix. Was the recommendation of over-seeding justified? Lessons for regenerating complex forages today. An article in the series on crop-grass diversification.

Imagine … you’re making a complex seed mixture by combining seed of each of the constituent species or varieties. You work out the best combination of species for the field – three or four for one-year’s hay and maybe 15 for long-term pasture – then gauge the ideal proportion of each in the resulting hay or pasture, e.g. 20% ryegrass, 10% red clover, and so on up to 100%. 

Four of the colour plates by L Schröter in The Best Forage Plants: left to right, kidney vetch, meadow foxtail, sweet vernal and alsike.

It was a complicated task. The composition of each species – in terms of protein, fat, fibre and so on – had to be known so that the mix would satisfy the purpose, whether hay or pasture, sheep or cattle. The amount of nutrients that each species would need from the soil had to be estimated. For example, a nutrient-demanding species might have a hard time in a nutrient poor soil or else starve other, less demanding species. Then the proportion of each species in the mix had to be calculated. And all this before science and farming were fully aware of soil-plant processes such as symbiotic nitrogen fixation. 

A major contribution to knowledge at that time was the work of FG Stebler in Switzerland. His book – The Best Forage Plants [1] – was written in German, co-authored by botanist C Schröter, translated into English by McAlpine [2] and the translation published in 1889.

There was great interest in grass-legume mixtures at that time. A shift from arable to grass had begun in Britain, initiated by serial bad weather and crop failure, coupled with unbridled cheap corn imports from the USA. It was the start of a long-term slump in arable farming and a rise in pasture husbandry [3]. 

The book described 30 species in detail: 21 grass and 9 legumes. Most would have been familiar in mixtures used in Britain, with few exceptions such as the legume Galega officinalis which they named Officinal Goat’s-rue (‘officinal’ because of its medicinal use in parts of Europe). 

Officinal Goat’s-rue, one of many colour plates by L Schröter in The Best Forage Plants, indigenous to south-east Europe but grown widely as a medicinal and forage, having a preference for warmth and deep soil, rarely sown as a forage in Britain.
How much seed of each grass and legumes species for a mixture

Stebler’s recommendations on seed rate (weight per acre) were not without controversy. He worked out from many field trials the seed mass of each species that would be needed to cover and produce good growth on an acre of field: for example, 38.6 lbs for perennial rye-grass, 18.5 lbs of cocksfoot, 22 lbs of lucerne and 15.8 lbs of red clover. (To convert to today’s units, 1 lb is 0.454 kg and 1 acre is 0.405 hectare.) So 7.72 lb of perennial ryegrass seed would be needed if its proportion was 20%.

His method went further by recommending that more seed of each component should be added than estimated by such simple proportion. The extra seed ranged from 10% to 80%, but was typically 50%. The reasoning was that the species in a mix occupy different parts of the space: roots exploring either deep or shallow soil layers, for example; or some species leafing early in the year, others later. 

This is what Findlay [4] in 1925, commenting on Stebler, meant by interlacing. The quote at the top of the page, from Findlay reads “As the roots and leaves of the different ingredients do not occupy the same places …. an allowance is made for interlacing.”

Grass specialists appreciated that roots and leaves of different species interlace: they enter each other’s space, they co-occupy ground. Several species might occupy the same area of ground but in doing so they are not always competing for the same resource or if they are then it is not in the same place or time. 

Is overseeding a waste?

Findley appreciated what Stebler meant, but went on to criticise the method. He wrote “at no time is there any connection between the proportion of the seeds sown and of the plants either in the hay or in the pasture”, and gave the example that a competitive grass will oust an uncompetitive one regardless of the proportions in the mix. 

Findlay was right in principle: the extent and type of interlacing depend on how the species react to each other in the local conditions. Yet over-seeding is not without merit. The aim of a seed mix was to get more mass or nutrition than could be had from any species grown alone. Stebler said that to do this you had to sow more seed of each component than that based on simple proportion. 

Take the very simple example of a 50:50 mix containing one grass or cereal and one legume. The legume fixes its own nitrogen (N) from the air, so will take little from the soil. Consequently, the cereal or grass has most of the soil N to itself, but if it were only sown at 50% of what it would take to cover the ground alone, then it might have a hard time extending its roots to get the N throughout the whole soil space, which includes that ‘under’ the legume. Therefore (Stebler would say) it should be sown at more than half the seed rate needed to grow it alone. 

That’s not the full story because the two species would also compete for other resources – solar radiation, water, the macro- and micro-nutrients. In a 15-20 species mix for permanent pasture, very many interactions would occur between the types, and some would result in the elimination of species. The ones that went would not be the same in all soils and climates. One purpose of a mix therefore was to build in redundancy, such that the mix would still perform well even if some components disappeared.  

Awnless Brome Grass, now named Bromopsis inermis Ssp. inermis, one of the many plates by L Schröter in the Best Forage Plants, capable on poor, drying soils, widely grown in Europe, also previously in Britain, but now rare here as a sown forage.
Postscript – Stebler’s influence ?

In his preface to the translation into English, McAlpine had the view that Stebler & Schröter, now accessible to English readers, would be seen as a major work of agriculture, leading to ‘a revolution in the forage culture of Great Britain’. Further on, he writes ‘I do not hesitate to affirm that if Stebler be destined as I believe he is to become a power in agriculture the effect will be to increase the production of good forage and to improve the practice of this most important branch of farming.’ 

Yet Findley in 1925 [3] found Stebler’s methods deficient in several respects and did not endorse them.  Whatever Stebler and Schröter’s influence on British forage might have been in the 1890s, it did not last. After the mid-1900s, mineral fertiliser would come to supply most of the nutritional needs of grass and supplant forage legumes such as clovers and trefoils. As described elsewhere, the diversity of grass forages became poor and probably the knowledge of how to manage multi-species grassland faded [5]. 

Recent decades have seen a part-reversal of that trend, in that grass-legume mixtures are increasingly available from seed merchants. Some of the mixtures are intended for grazed swards but the emphasis seems to be on restoration for wildlife conservation. 

The lesson from Stebler is that the basis of estimating seed rate in a mixed crop or pasture might need to be reconsidered. In many parts of the world, however, seed is not plentiful. The choice has to be made: eat the grain now or keep it to sow for the next crop.

To come …. More on Stebler & Schroter’s Tables on the nutritional value and needs of grass versus legumes. 

Sources / references

[1] Stebler FG, Schröter C. ‘The Best Forage Plants’. Translated into English by A N McAlpine, 1889. Publisher: Nutt, London. Available to read online through Google Books. The illustrations of grasses, some reproduced here, were by L Schröter, brother of the second author. A review of the book, Wrightson J. (1889). A Review of The Best Forage Crops. Nature 39, 578-579, tells readers that the treatise omits the common fodder crops such as vetches and brassicas, and deals mainly with pasture grass mixtures. 

[2] A N McAlpine, the translator of Stebler & Schröter into English, was Professor of Botany, New Veterinary College Edinburgh and Botanist to the Highland and Agricultural Society. 

[3] curved flatlands article: Food security in the pandemic.

[4] Findlay, W M. 1925. Grassland in Scotland. In ‘Farm Crops’ edited by W G R Paterson. The Gresham Publishing Company, London. 

[5] curvedflatlands articles: Grass mix diversity a century past – for reference to books by RH Elliott and H Stevens; and 1800s mixed crops – lessons from the Agrostographia – gives examples of the Lawson’s (Edinburgh) crop and grass mixtures. 

Acknowledement Thanks to K Owen for allowing the use of her depictions of interlacing on Pictish symbol stones.

1800s mixed crops – lessons from the Agrostographia

The 1800s, especially the first three quarters of it, was a period of notable invention and experiment, building on the gains from the first phase of Improvement that began a century earlier. Mixtures of crops, of grass and of crops and grass together are repeatedly referenced in the various books and manuals published throughout the period.

Several of these mixtures are examined here, as possible pointers and templates for modern attempts to re-diversify agriculture. The main sources are those published by the Lawsons, seed merchants based in Edinburgh, notably their Agrostographia [1, 2], which appeared in various forms from 1833 to 1877. For example –

  • barley-sainfoin (cereal-legume) mixture, the barley sown as a ‘nurse’, sainfoin drilled at right angles to the barley (a line intercrop?)
  • barley-oat-weld, the first two harvested after the first season, the weld yielding the next year.
  • within-species field bean varietal mixtures.
  • legume-legume, for example, field bean and vetch/tare.
  • barley, oat or any corn sown with grass as a nurse to protect the more valuable grass-legume sward.

As in other articles on this web site about our cool-climate mixtures, all crops were sown as seed mixes rather than line or row intercrops (with the possible exception of barley-sainfoin).

Barley-sainfoin gridded at drilling

When considering which dicot forages to recommend, Agrostographia suggested that sainfoin Onobrychis sativa could be grown in several parts of Scotland, though it was primarily grown in more southern climates. It likes a ‘dry’ and well drained soil, and was also recommended as an addition to their perennial pasture mix on calcareous soil.

Barley and sainfoin are sown together, drilled at right angles, the barley growing quickly, ‘nursing’ the other, then harvested in late summer for grain or fodder. Sainfoin overwinters in the barley stubble, then grows into a full forage crop the next year, when it is cut for fodder. It regrows and is repeatedly cut for several years. Original drawings by K Owen.

As a sole forage, it sometimes suffered in the first year. Therefore to aid establishment, the Lawsons pointed out the practice of sowing a nurse crop, such as barley, first. Then in those situations where that crop was drilled, the sanfoin was drilled at right angles to it, in effect forming a grid, rows of sainfoin crossing rows of barley. The barley was harvested in the first year, as cereal grain or forage crop, leaving the sainfoin to over-winter as a small plant, then extend and flower the next year. It would have been cut one or more times in the summer of the second year, after which it became a perennial forage.

This practice presumably prevented the second drilling (that of the sainfoin) from interfering too much with the first. It might have created an interesting pattern if the drills were reasonably wide apart.

Unlike many mixed crops, the aim of this one was to encourage the legume to establish. Barley would have been sown at a smaller seed weight per acre than when sown for a sole crop, so as to form enough cover to protect the sainfoin without completely denying it light and nutrients. It is unclear whether any particular advantage came to the barley, since it would grow much faster than sainfoin in the first year. No information is available from that time on nodulation in the legume and whether it released any fixed nitrogen when the barley needed it. In recent experience, sainfoin grows luxuriantly at 58N, withstanding the mild maritime winters without any obvious setback [4].

Field bean variety mixtures

In their Agriculturists’ Manual (1836) and the later Synopsis (1852), the Lawsons’ list varieties of Vicia faba of which the main one grown at that time was named Common Scottish or Horse Bean. They write: “Beans enter the rotation of cropping in the early districts of Scotland, and are very successfully cultivated on all strong soils, forming an excellent preparation for wheat. The straw or haulm forms nutritious food for horses during the winter and spring months.”

This comment – on the successful cultivation of beans – contrasts with the decline in area of this crop, along with many other arable crops, during the economic depression after 1880 when agriculture made one of its shifts to grass, on this occasion because of low global grain prices.

Page from the Lawsons’ Synopsis of 1852 showing the description for Common Scottish or Horse bean, the 295th entry (after the cereals but before the forages and fruits).

The point of interest here is the comment of what appear to be crop variety mixtures, identified by the range of flower colour. The wording in the above is little different from that given in the earlier 1836 Agriculturist’s Manual, and extract of which is given below.

The authors could not be certain that the fields they referred to were intentionally sown mixtures. Many of them would have been landraces, maintained by farm-saved seed, or seed impurities or even ‘volunteers’ (which arise from seeds shed by a previous crop and emerging in the current crop). Certainly, faba bean today readily gives rise to short-lived volunteer populations on waysides and in fields of other broadleaf crops..

This note from the Lawsons’ experience shows that despite the seedsman’s quest for purity in seed stocks, diversity was hard to eradicate.

Barley-oat-weld – grain and dyestuff

The plant weld Reseda luteola was once cultivated widely for the yellow dye that can be extracted from its leaves, stems and flowers. Weld as a commercial product has been replaced by imported dyestuffs, but it remains a common wild plant, sometimes growing by roads and especially on wasteland and old industrial sites.

As a crop, it was typically sown in spring along with a corn, such as oats or barley. When they were harvested in autumn, the weld was left to overwinter, then harvested the next year. The plants “are pulled when in flower, or before the seed is fully ripe, and used either in a green or dry state” [3]. Thirsk [5], writing about weld cultivation in 1600s England, relates a similar sequence: barley or oats sown (sometimes buckwheat), weld harrowed in, the corn harvested in autumn and the weld “pulled up by the roots, dried and stored the next year”; and then an usual variation in Kent, weld undersown in barley, the field used for grazing in autumn and the weld again harvested the next summer.

The diagram shows barley and oat grown as a corn mixture, weld seedlings growing beneath them in the first year then weld plants flowering among the corn stubble the next summer [4].

Barley, oat and weld sown as a mixture in spring, the two cereals growing more quickly and harvested during the first summer for grain or fodder, weld much slower and lower. Weld over-winters as a ‘rosette’ then extends the next spring into a flowering plant, harvested green for dyestuff. Original drawings by K Owen.

Two legumes: field bean and common vetch

Agrostographia also describes an unusual mixture – the bean Vicia faba and a forage legume, common vetch Vicia sativa (also known as common tare). Common vetch, as were many other vetches and tares from the genus Vicia, was grown as a commercial fodder crop. Its cultivated forms were reported to be different from the smaller and more slender local wild form. The Synopsis [3] distinguishes the common or summer variety from the winter variety, and also the Hopetoun Tare, which appears to be a landrace selected from a field of the summer variety.

Common vetch was grown as a green fodder and also for seed. Agrostographia describes two types of crop mixture. In one, the vetch is sown with cereals. Agrostographia writes: “The practice of sowing one or other of the cereal grasses (oats or barley) among Tares is strongly recommended, not only as it ensures a greater bulk of produce from the stems of the grains rising above the Tares, but they also serve to prevent them lying on the ground, and so becoming injured in damp weather; cattle are also fonder of the fodder in a mixed than in an mixed state.” It appears from this statement that the mixed crop has at least three advantages: more grain from the cereals, support to keep the vetch off the soil and a more nutritious (balanced) fodder.

In the other mixture, vetch is grown with field bean. Two legumes – but the benefit of sowing them a mixture is unclear. Agrostographia: “When sown for their ripe seed, the Summer Tare is generally mixed with beans, or peas and beans, in the proportion of about a fourth part in bulk, or less …”. In contrast, the winter vetch, sown in autumn for seeds, was said to be generally sown alone, but the manual advises they should be sown with winter bean – “… the seeds being easily separated from the beans, when thrashed, by means of a proper sized riddle”. The beans must have given the vetch support as did the cereal crop in the other type of mixture, but what benefit came to the beans?

Corn as a nurse for grass

The main type of mixture described in Agrostographia was that of ‘grass’ comprising grasses, legumes and other dicot (broadeaf) plants. These highly diverse seed mixtures were generally more valuable and more costly to establish than crop mixes, but also more open to damage in the weeks and months after they were sown. To help grass mixtures to establish, they were sown with a corn crop, oats or barley, which was harvested or grazed after it had done its job of nursing the grass seedlings.

More on grass mixtures and corn nurses is given at Grass mix diversity a century past. Further articles on this theme are in preparation.

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Sources, references, links

[1] Agrostographia; a treatise on the cultivated grasses and other herbage and forage plants. Authors: The Lawson Seed and Nursery Company. Successors to Peter Lawson and Son. Date: 1877 (6th Edition, by David Syme, Manager). Publisher: William Blackwood & Sons, Edinburgh and London. Online through sources such as the Biodiversity Heritage Library. Information in the Agrostographia was first published in 1833, though not under that name, and then as part of The Agriculturist’s Manual in 1836 [3].

[2} Agrostographia as a title is of much older origin, being that of a major compendium on grasses written in Latin, by or edited by, Johannes Scheuchzer (1684-1738), published 1719, edition of 1775 viewed. Scheuchzer is credited with being a founder of the science of Agrostology – the study of grasses.

[3] The Lawsons’ Agriculturist’s Manual (1836) and Synopsis (1852), the latter an expanded version of the Manual, are invaluable sources for 1800s crops and their varieties, both available online, e.g. through the Biodiversity Heritage Library. Details:

The Agriculturist’s Manual. Peter Lawson and Son 1836. Edinburgh, London and Dublin. Being a familiar description of the Agricultural Plants Cultivated in Europe including practical observations respecting those suited to the Climate of Great Britain; and forming A Report of Lawson’s Agricultural Museum in Edinburgh (Seedsmen and Nurserymen to the Highland and Agricultural Society of Scotland).

Synopsis of the vegetable products of Scotland. Peter Lawson and Son. 1852. Private Press of Peter Lawson and Son. Prepared for the Great Exhibition and dedicated to William Jackson Hooker, Director of the Royal Botanic Gardens of Kew.  

[4] Sainfoin was grown in the Living Field garden at the James Hutton Institute, Dundee, for several years. It grew slowly in the first year but overwintered successfully and then flowered in the second and subsequent years. Weld grows easily at the Living Field, either flowering the same year as sowing or overwintering and flowering the next year. A mixture of oat, barley and weld was sown on one occasion but the weld failed!

[5] Thirsk J. 1997. Alternative agriculture: a history – from the Black Death to the Present Day. Oxford University Press.

Non-serious depiction of a barley-sainfoin mixture to show the practice of drilling barley in one direction then drilling sainfoin at right angles. Described in Agrostographia 1877. Images from plants grown in the Living Field Garden, Dundee.

form line, form square? … naargh just mix it!

Formal and informal mixed cropping. Mixed corn and mashlum (oats, beans) preferred historically in Scotland, seed mixed not sown in lines or squares. By mid-1900s, covering very small areas of cereal land. Dredge corn from SW Britain.  Unintended mixed grain from volunteer weeds. Mixes grown as a safeguard. Lessons from history.

Archaeological evidence from many landscapes across the globe shows agricultural land divided into geometric shapes. Linear features may have been constructed as drove-ways to move stock from one piece of land to another; or for cultivation by teams of animals dragging a plough that was difficult to turn. Squares or or other shapes with conserved side-length, are preferred when something has to be contained, such as stock animals or valuable crops that can be surrounded by a wall or fence.

Similar features occur when more than one species of crop is grown in a field. Such intercropping or mixed cropping is widely practiced in many agricultural regions. Smallholder gardens will often consist of small blocks, sometimes even single plants, grown close to each other, sometimes under the shade of a tree-crop. Perhaps the most widely observed configuration is that of lines or rows. One species might occupy one or more adjacent lines, then another species then back to the first species, as in the example below of an intercrop of chickpea and sunflower [1]. 

Chickpea field in which lines of sunflower have been sown, Burma (Myanmar), image by curvedflatlands.

Not all mixed crops are grown in formal configurations. Seeds can be mixed in the bag or mechanical sower and broadcast on the land. Two or more species then emerge together to form a mixed stand.

Also, unintended mixtures can occur when seed dropped on the soil by previous crops emerges in a later one (see below). Whether unintended or planned, simple mixtures have been recorded in agriculture since records began.

A new dawn for mixed cropping in Atlantic Europe?

Three factors need to be assessed when considering the (re)introduction or expansion of mixed cropping. One is whether a biological advantage results from growing the species in a mixture: if there is, the grower gets more from the land or resources than they would if the crops were grown alone over the same area. A second is whether the mixture provides a convenience: even without a biological advantage, it might simply be easier for sowing and harvesting to grow two or more crops in a particular configuration, especially if the grower wanted a varied output (e.g. cereals, legumes, fruit, vegetables) from a small plot of land. The third is whether the mix provides a safeguard or security against unexpected events: here, a biological advantage and ease of management may combine to ensure something is produced.  

The type of mixture used in previous times may also be a practical guide to what might still be feasible. In Scotland, and elsewhere in Britain, the most common sown mixtures from the 1700s to the early 1900s were intended for hay and grazing. They were rarely ‘grass only’, but comprised grasses, legumes and other broadleaf species in proportions varying with the intended use [2]. The legumes in the mix, the most abundant being white and red clover, fixed much of the nitrogen used by subsequent grain crops.

Also references are repeatedly made to assorted mixes of corn and grass, where barley or the landrace bere was sown as a ‘nurse’ for the more valuable and longer lasting hay or grazing mixture [3].

Mixed arable crops (no grass) were also mentioned in sources from the 1700s and 1800s, mainly as sown seed mixtures, very rarely if ever as line intercrops. But by the time formal agricultural census began in the later 1800s, sown crop mixtures such as mixed corn and mashlum were grown over a very small area. 

Mixed corn, dredge corn and mashlum

The two most widely grown crop mixtures in the north of Britain go under the names mixed corn or mixed grain and mashlum. Mixed corn consists of two or more cereals, barley and oats for example, while mashlum consists of a cereal and a grain legume, typically oats and beans (Vicia faba). Mashlum reached its 20th century peak during WW2 (Fig. 1). The subsequent fall but continued usage of mashlum was documented on the Living Field web site [4].

Mixed corn or mixed grain appeared as a separate entry among grain crops in the Agricultural Census of 1929 [5]. Its area expanded and contracted over the next 50 years but generally remained less than 0.05% of the combined cereal area (Fig. 1). There is little information of why mixed corn was grown and also why its area was so small. Oat dominated the cereals in the earlier part of the period shown, then gave way to barley and wheat. 

Fig. 1. The areas sown with mixed corn and mashlum in the Agricultural Census for Scotland [5]: mixed corn not identified from other cereals before 1929 and after 1978; mashlum grouped with other forages before 1944 and after 1960. Over the period shown, mixed corn comprised less than 0.05% of the combined cereal area.

Cereal mixtures grown elsewhere in the UK offer some explanation. A mixture of barley and oats named Dredge Corn was a feature of arable in the south west, mainly in Cornwall [6]. Its area was uncertain due the fact it was returned as ‘barley’ before 1919. As the quote at the top of the page implies, it was used as a safeguard, to ensure a reasonable yield under most conditions. It had a place in the crop rotation, sometimes replacing oats, sometimes barley, and was used in particular for a whole crop feed when the soil or the year was not capable of producing a pure crop of quality to sell as grain.  The proportions varied but were typically two parts oats to one barley. Wheat was added in some cases, making a three-part mixed grain.

While it was certainly grown as a safeguard, it was also attributed biological benefits [6]. It was stated to produce more grain than barley alone and generally more than oats alone, oats being deeper rooted and thereby accessing more resource. In dry years, barley grew to fill the ‘gaps’ left by dying oat tillers. The straw was of higher feeding value than the individual crops, due to better overall structure. But perhaps most relevant to the Atlantic climate, the mix was better able than barley or oat alone to withstand the forces of wind and rain to flatten the crop.  Similarly, one source reported that another variant – a mix of white and black oats – gave a greater yield (of straw) than either alone – the stronger stemmed white supporting the finer stemmed black. 

Despite such reports from farmers, there is little hard information on the yield advantage given by mixtures sown on the fringes of Atlantic Europe. They might have given the 1.1. to 1.3 times advantage widely recorded for intercrops, but without the experimental data from the 1920s or earlier, there is no way of knowing. 

Sown as a seed mix in April, no fertliser or pesticide: (left to right, 1 to 4) the bere barley grew quickly (1), then oat pushed through (2), bere matured first (3) and finally oat (4).

The widespread occurrence of unintended mixtures

It is the nature of small-grained cereals – oats, barley, wheat – to drop seed before or at harvest. The seed remains in the soil and, depending on conditions, emerges in a later crop. Today, such crop-weeds are commonly termed ‘volunteers’ [7]. The sown species and the volunteers in effect form a mixed crop (image below for wheat in barley). Other crops also generate volunteers. Those of oilseed rape are the most visible, but potato and field bean (Vicia faba) often produce mixed crops with cereals, though these broadleaf species may be really controlled by selective herbicides today. 

Unintended mixed crops have been a feature of cereal lands probably since domestication. If the intended product was whole-crop cereals to be fed to stock, then they would have been seen as a benefit – free seed. However, they may also create a problem. They are an unwanted nuisance when they have to be separated from the crop, for example when a pure seed-harvest is needed, and they could harbour and carry over disease. Volunteer cereals are not a recent problem: records from the 1500s [8] on oats relate “that they grow amongst wheat and barley without being sowen, as an evil and unprofitable thing ..”.

Maturing barley crop, golden brown, in which volunteer wheat (upright heads, dark grey-green) has established; younger, still green plants growing in the wheel lines.

Conclusions

Mixed corn, and mixtures of corn and grain legumes, have been recorded for centuries in Scotland, and more generally in Atlantic Europe, but their benefits have not been adequately quantified. Where they were grown, it was as broadcast seed mixtures rather than line intercrops. By the early 1900s, they were minor crops. After the 1940s, agriculture was aiming for the high yields promised by intensification: mixtures almost disappeared. 

Current reappraisal of crop mixtures might perhaps examine why in the early 1900s they never became major crops and why they were rarely grown as line intercrops.

Sources

[1] Photograph of chickpea-sunflower intercrop taken in Burma (Myanmar). Details on curvedflatlands at Mixed cropping in Burma.

[2] Seed mixtures for hay or grazing from the 1700s to the early 1900s are described in a related article on curvedflatlands: Grass mix diversity a century past.

[3] Crop mixtures are frequently referred to by Andrew Wight in the Present state of husbandry in Scotland (1778-84. Volumes 1 to 6), where one of the components (usually bere or barley)  is most commonly a ‘nurse’ crop, protecting the others, which are usually grass mixes (grasses, legumes and other broadleaf species) to be used for hay or grazing. 

[4] Mashlum, Scotland’s cereal-legume seed mix, still occasionally grown, is described on the Living Field web pages at Mashlum – a traditional mix of oats and beans  and Mashlum no more! Not yet.

[5] Data in Fig. 1 are taken from the online Agricultural Statistics in Scotland one of the Historical Agriculture Publications on the Scottish Government web site. Based on the 1965 census, Coppock created an atlas in which the small area sown with mixed corn was noted with the comment that it was ‘not grown in the great majority of parishes’. Ref: Coppock, JT. 1976. An agricultural atlas of Scotland. John Donald, Edinburgh.

[6] Borlase, W. 1925. Dredge corn. In: Farm Crops, Vol 1, pages 265-269.

[7] Volunteer weeds, derived from crops, and presently common in Scotland  are described at the Living Field web pages on Crop-weeds.

[8] Quote on oat from L’Agriculture et Maison Rustique by Estienne and Liebault, 1593 edition. Further details and origin on the Living Field web pages at: Ready, steady mundify (your barley) and  The Library of Innerpeffray.

 

 

Grass mix diversity a century past

Innovative seed mixtures from the early 1900s based on functional properties of species. Legumes around 20% of seed mix by weight. Increasing complexity to suit purpose and longevity of the sward. De-diversification in the last 100 years. One of a series of articles on crop-grass diversification.

Diverse grass fields were once a common feature of the agricultural landscape. Mixtures of grass, legumes and other species were widely trialled and adopted in the Improvements era after 1700 [1]. Mixtures were promoted throughout the late 1800s and early 1900s, the topic of this article.

The aim of mixtures was to provide a balanced diet for livestock and to regenerate soil condition and fertility. Nitrogen-fixing legumes in mixtures had the specific roles of enriching soil with nitrogen, before mineral fertiliser came to be widely used from the mid-1900s, and offering livestock a high-protein bite compared to the grasses.

Most traditional meadows have now been converted to fertilised grass or crop. Much of the grass now grown for hay or pasture consists of one or two grass species, with occasionally white clover and often some noxious weeds. Legume forages are now uncommon. Managed grass is usually supported by mineral fertiliser and by imports of high-protein legume-based feed supplement.

Grassland. Shapinsay, 27 May 2019

Change may be afoot! Recent EU funding rounds have brought together researchers and specialists to design and trial new food and feed systems which aim to reverse some damaging trends both in the field and the wider food supply chain [2]. Part of the solution is a re-diversification of agriculture.

To explore some of the main current themes, the Living Field [3] and this web site are running a series of articles on diversification in land use and food production. Many of the forgotten practices of the past are still relevant. Here we look at the structure of diverse ‘grass’ mixtures recommended in the late 1800s and early 1900s.

Groups and species

Traditionally in Scotland, managed ‘grass’ (as distinct from rough grazing) was rarely just left as permanent, untended grazing land. It was either sown for hay or pasture over one, two or three years or left longer as ‘permanent’ grass, but even the latter was usually re-sown after a time to re-introduce species forced out by the more competitive grasses. Published in 1925, W M Findlay went into some detail on how grass mixtures were managed, but the specific interest is that he described mixtures in terms of the mass of seed of each component species [3].

Fig. 1 A seed mix made up of grass (blue-green) and legume (red): the inner circle showing all grass and all legumes; the outer circle showing two grass and two legume species.

The lists in Findlay are here presented as circular diagrams of the type illustrated in Fig. 1. The inner circle shows the percentage of seed from the grass family (blue – green) and the legume family (red). The outer circle shows the percentage seed of each species of grass or legume, individual species distinguished by different colours or shades.

In the example shown, the grass makes up about 80% and the legume 20%. There are two species of grass and two species of legume. This is a simple mixture but is still more diverse than many grass fields today.

Cattle on rolled hay field, Inverness-shire, 22 June 2019

Mixtures of increasing complexity

Four mixtures are shown in Fig. 2, the one top left is that from Fig. 1 but with species indicated. It is a mixture recommended for one year’s hay, after which it will be cultivated and turned to arable or transformed into another mix. The next three, moving clockwise, are mixtures of increasing complexity – top right is for two years’ grazing,  lower right for hay followed by grazing and the lower left for permanent grass.

The number of species increases in both grass and legume categories from top left clockwise. The permanent grass mix contains a third category – broadleaf or ‘dicot’ species that are not legumes (orange brown). Of the latter category, chicory and yarrow are included but not plantain which was commonly sown in ‘grass’ mixtures in the Improvements era.

Fig. 2 Four ‘grass’ seed mixes of increasing complexity from top left clockwise, intended for different purposes shown above each circle. Plant species and their proportions, based on sown seed mass, are indicated by different blue-green colours for grasses, red for legumes and orange-brown for broadleaf-but-not-legume plants. Original data in Findlay (1925)

In all categories, grass occupied about 80% (four fifths) of the mixture and legumes 20%, or a little less in permanent grass. The legumes include red clover (two forms), white clover (including a ‘wild’ version), alsike and kidney vetch. The permanent grass mix also has chicory and yarrow.

Findlay also gives an example (Fig. 3 here) of one of R H Elliot’s mixtures from his book Agricultural Changes (1898) which was later published as The Clifton Park System of Farming [5]. Notable in Elliot’s mix is the presence of legumes but also the much greater proportion of other broadleaf plants, most of which were included for specific functional properties [6]. Findlay does not agree wholeheartedly with Elliot’s recommendations, relating for example from his own trials that some of the broadleaf plants did not penetrate a hard soil pan, as Elliot suggested they would.

Fig. 3 Proportions of main groups and species in one of Elliot’s seed mixes [5] given in Findlay [4]: grasses, blue-green; legumes, red; other, orange yellow.

The proportion of seed in mixes was based on trials to assess how much seed of each was needed to cover an acre. Then seed mass was adjusted to suit the balance in the mixture, seed size and germinability and whether hay (flowering heads, less dense) or pasture (leaf, more dense) was the aim.

Were native plants used? Many of the grasses and legumes are native to Britain, but there was an international trade in seed then as now. Many varieties were imported for testing and usage. Over time, lays and pastures would have become a mix of native and imported populations.

The mixtures recommended by Findlay and those by Elliot are based on serious investigative studies that imply a sound knowledge of plants. They were devised at a time before mineral nitrogen fertiliser became cheaply available and among the primary aims of the mixtures was to increase the ‘health’ and fertility of soil as well as feed livestock.

Hay field recently cut & baled, Carse of Gowrie, 20 July 2019

The contribution of nitrogen fixing legumes

By the early 1800s, forage legumes had become standard in sown grass mixtures.  Writing well before Findlay and Elliot, H Stephens in The Book of the Farm [6], first published 1841,  gave weights of the grasses and legumes in mixtures designed for a range of purposes. (The author farmed in Angus for part of his life.) Stephens gives the seed weights for mixtures suited to various durations and conditions: he even includes all-legume mixes and his short-term lay contains about one-third legumes by seed weight.

In all these accounts, the main forage legumes were red clover Trifolium pratense in various forms and white clover T. repens. Others referred to by these authors, included in mixes for specified durations and soils, were alsike T. hybridum,  suckling clover T. minus and crimson clover T. incarnatum (the latter generally considered unsuitable for northern latitudes of Britain but will grow here).  Other species were the medic or hop-trefoil Medicago lupulina, bird’s-foot trefoil Lotus corniculatus,  lucerne Medicago sativa and kidney vetch Anthyllis vulneraria.

These are by no means the only ones trialled in Scotland. There was clearly a thirst in the 1700s and 1800s to explore a wide range of species before settling on the clovers. In The Book of the Farm (1908 edition revised by MacDonald), they write about clovers:

” …. the most valuable herbage plants adapted to European agriculture – the white and red clovers. Notwithstanding what has been said of the superiority of lucerne, and of the excellence of sainfoin in forage and hay, the red clover for mowing and the white for pasturage, excel, and probably ever will, all other plants.”

Despite the uncertainty in how seed mass translated to plant mass, Findlay provides one of very few quantitative descriptions of the proportion of nitrogen-fixing legumes in a mix from the period shortly after WW1 when the scientific study and practice of agriculture was becoming established.

Clovers used in grass mixtures: (top left c’wise) red, white, crimson with white, crimson flower and alsike.

Mixtures were planned based on functional characteristics

The mixtures suggest there was a practical understanding of how species would interact when growing in a field. The author points to eight different properties that should be considered in choosing a mix.

  • Adapted to the local soil:  particularly to sandy or peaty soils.
  • Longevity: early or fast growth coupled to short life, e.g. red clover not expected to survive in permanent grass.
  • Habit of growth: a correct mix of ‘top’ plants that provide much of the fodder and ‘bottom’ plants that cover soil and ensure no gaps.
  • Time of year: a correct mix of developmental phases to ensure growing foliage is present for as long as possible.
  • Readily eaten by stock: (fairly obvious but) need to avoid plants that are less palatable or which become unpalatable with age.
  • Feeding quality: (again fairly obvious but) need by experience to assess quality depending on local conditions and manage so as not to diminish quality (and Findlay admits that quality was at that time difficult to measure).
  • Must die when ploughed: so as not to occur as weeds in subsequent crops (less important if permanent pasture is the aim).
What happened next?

One of the great uncertainties in defining agricultural trends is how the composition of grass mixtures changed since the annual census began over 100 years ago. Whereas, the areas sown with grains such as peas and beans were recorded [8], legumes in grass mixtures were not recorded. The census restricts managed grassland to the two main categories, short-term and ‘permanent’. For a time, the census also recorded the proportion of each used for hay or grazing.

There has been no consistent recording of the composition of grass, so the trajectory from the recommendations of the 1920s to the present is unknown. Yet travelling around the country, observing grass and crops, usually from the other side of the fence, leads to the conclusion that most current grass is far from diverse. In some fields there is one or two species, typically perennial ryegrass and timothy. Legumes except for the occasional white clover are absent. In the main, managed grass in Scotland has been de-diversified.

But not all of it …… [Further articles in this series will look at remaining sources of grassland diversity in low-input and organic farming and in commercial seed mixtures.]

 Sources, references, links

[1] Andrew Wight’s travels in the late 1700s describe first hand the improvements in field practice that commonly included sowing mixtures of grasses, legumes and other plants. Available online: Wight, A. 1778-1784. Present State of Husbandry in Scotland. Extracted from Reports made to the Commissioners of the Annexed Estates, and published by their authority. Edinburgh: William Creesh. Vols I-VI (e.g. search for title in Google Books).

[2] Recent EU research funding in agricultural and food systems is distinguished by the inclusion of a wide range of small enterprises that will be effective in rediversification. Agroecology at the James Hutton Institute (Dundee, UK) is leading several EU initiatives of this type including TRUE true-project.eu and Diversify plant-teams.eu.

[3] The Living Field project www.livingfield.co.uk at the James Hutton Institute promotes outreach and education. Its garden near Dundee displays many of the plants grown for food and feed, including most of those noted above.

[4] Findlay, W M. 1925. Grassland in Scotland. In ‘Farm Crops’ edited by W G R Paterson. The Gresham Publishing Company, London.

[5] Elliot RH. 1898. Agricultural Changes, later published as The Clifton Park System of Farming. Available online at journeytoforever.org.

[6] Stephens H. 1841. The Book of the Farm. Blackwood, Edinburgh. Printed in many subsequent editions in the later versions of which, revised and re-written, it was named Stephens’ Book of the Farm. Available online from various sources.

[7] Most plants in Fig. 2 and Fig. 3 are recognisable from the common names given by Findlay.  Burnet probably refers to fodder burnet, now given the botanical name Sanguisorba minor and recognised as subspecies muricata to distinguish it from salad burnet (subspecies minor).

[8] Trends in grain legumes and the benefits of increasing their presence in modern agriculture and food supply chains are examined by: Squire, Quesada, Begg & Iannetta. 2019. Transitions to a greater legumes inclusion in cropland ….. Food and Energy Security https://doi.org/10.1002/fes3.175 doi (available free online).

Author/contact: geoff.squire@outlook.com or geoff.squire@hutton.ac.uk.

Funding  The author currently has honorary (unfunded) status at the James Hutton Institute. A background knowledge of crop-grass mixtures was gained in past years through funding from the Scottish Government Strategic Research Programme and EU projects, mainly TRUE [2].

Resilience in a three-grain production system

Summary 

Cereal farming in the north Atlantic region improved to a point in the mid 1900s where starvation and famine were a distant memory. Half a century on from then, impending pressures through soil, climate and economics are threatening stable and reliable grain production. Yet the dire predictions of some commentators are unlikely to happen. Cereal farming has repeatedly adapted and survived since the first settlers brought grain to these islands.

This article summarises the changes that have occurred over the past century and suggests the system has in-built resilience through its combination of three grains – oat, barley and wheat. 

Cereal country, Scottish Borders, August during harvest (@curvedflatlands)

Cropland in the northern part of the British Isles has grown barley, wheat and oat as its main cereal grains for thousands of years. Barley and wheat have been recorded since the neolithic, oats perhaps later. Cultivation of all three has sustained people and had been demonstrably sustainable, in that it continues.  There is no reason in principle why it should not continue well into the future.

Until the mid-1900s, these three home-grown grains were the main food of people and livestock. Other crops such as rye have occupied little area. However, at no time were the areas or proportions or uses of these crops fixed. Rather, they have changed as part of long term societal trends and over shorter time scales in response to international markets and bad-weather years.

In 1900, oats dominated. Then the next 100 years saw major changes in the proportional area of the three cereals (Fig. 1).

Fig. 1 The proportions of oats, barley and wheat in selected years of the annual agricultural census for Scotland [1, 2]. In 1990 and 2018 w and s refer to winter and spring barley.

It is sometimes assumed that the period of agricultural intensification following WWII, and operating mainly between 1960 and 1990, caused the greatest upheavals in the history of agriculture, but major change in crops and output occurred during the Improvements after 1700 and then in the later 1800s.

Winter wheat, ripening in late August (@curvedflatlands)
Change at the turn of the century – 1900

Figures taken from the official agricultural statistics from 1883 [1] show a steady decrease in the area grown with arable crops compensated by an increase in the area of ‘permanent’ pasture. The total land area grown with all crops and grass was more stable.

In just less than two decades before 1900, around 10% of the cereal area was lost to grass. Turnips and swedes – the winter lifeline for people and stock since the 1700s Improvements – had begun a steady descent that was to continue well into the next century, and the grain legumes – peas and beans – had even then become minor crops.

Fig. 2 Proportions of the three cereals in 1900 at a time when the area of grass was rising and arable (tilled) crops was falling. The area grown with cereals is shown under the pie diagram [1].

Symon labelled the period 1875-1914 ‘Forty bleak years’ [3],the bleakness caused as least as much by international trade pressures and inequalities in local society than anything biophysical. Yet he pointed to Scottish farming being ‘elastic’, enable to withstand the shocks of depression due to the three grains and the varied stockraising.

In and around 1900, oat occupied about three-quarters of the cereal area, barley around 10% and wheat the rest. The proportions of the three cereals changed little until after WWII. Economically, oats was less profitable than the other two but was hardier and easier to grow on the little nutrient resource available.

Spring barley, sown early, photographed 24 April, Angus coast (@curvedflatlands)
Intensification 1960 to 1990

The hard lessons of agricultural insufficiency in 1914, repeated in the 1940s, led to government-backed programmes for agricultural improvement, which also took advantage of new opportunities for international trade and technological advances [4]. Deeper cultivation allowed roots to explore an increasing volume of soil. Mineral nitrogen fertiliser became widely available and relatively inexpensive; and from the late 1970s chemical pesticides proliferated to control the many weeds and diseases that sought their share of the nitrogen! New cultivars were introduced with higher yield potential, mostly through a larger the grain ‘sink’, allowing a rising harvest index (grain/total mass).

Fig. 3 Proportions of area (pie diagrams) and total area (figures beneath) sown with oats, barley and wheat in 1945 and 1990. Barley in 1990 is separated into winter and spring varieties [1, 2].

The results of intensification were stunning. Cereal yields increased sharply from the 1960s. Most of the wheat was autumn sown, as was a proportion of the barley. Together these ‘winter’ crops came to occupy about 20% of the total cereal area. Compared to spring barley and oats, they were in full leaf at the time of peak solar income in late May, June and July. This shift in timing enabled them to accrue more photosynthetic mass to feed their higher grain ‘sink’.

Barley and wheat became more profitable as sources of alcohol and stockfeed. Oats – the only one of the three now used to feed people – declined to an area equivalent to that of wheat a century earlier. Most other cereal carbohydrate eaten by people is imported as bread, pasta, rice and maize.

Winter barley ready for harvest, late July, Borders (@curvedflatlands)

A quarter century of level output

During intensification, the area grown with cereals recommenced its pre-war decline (Fig. 3). By 1990, the cereal area was 90% of that in 1945.

But another and more significant change occurred. By the early 1990s, the rapid rise in yield due to intensification came to an end in the main cereal areas (for reasons that are not entirely clear). Yield increased a little over the next decade but then more or less levelled. Despite many technological advances, the rise in yield that began in the 1960s had been halted [3].

A similar pattern of levelling outputs has occurred in many parts of Europe and much farther afield. Is all now stagnation and decline?

Not quite. Recent records of yield and sown area suggest that while yield may be sensitive to bad weather years, such as the wet 2012 and dry 2018, farming has a capacity to shift land between the three cereals to offset the worst the weather can throw at it. Moreover, the yield per unit area of oats has increased to become close to that of spring barley [5].

Despite cereals giving poor economic returns at this time, the system is not mired and should be still able to respond to the inevitable impending change.

Whole-crop oats, being cut 30 July, Orkney (@curvedflatlands)
External and internal pressures / capacity for adaptation

The cereal- and grass-based croplands of lowland Scotland face a set of internal and external pressures to which they must adapt. They include –

  • internal degradation of soil, element cycles and food webs due to intense cultivation, a factor likely to increase pressure on surrounding ecosystems but also to decrease the capacity of land to yield;
  • climatic change and extreme events of the type that dented output in 2012/3 and 2018;
  • continued reliance on external sources of nitrogen and phosphate fertiliser;
  • further pressure on the economic  position for mass-market grain, for example, owing to competition from other countries, trade wars and blockades.

One threat that should be no longer feared, however, is that of repeated crop failure, starvation and famine that hit parts of the country as recently as the mid-1800s. And there are increasing positives –

  • Greater demand for home-grown cereal products, for example through an increased desire for local, sustainable food and drink.
  • Technical innovations in cereal varieties and agronomy that open new higher-value markets.
Winter wheat ripening before harvest, late August, Borders (@curvedflatlands)
Retaining flexibility

The line of census records since the early 1880s has shown massive shifts in the total and relative areas cultivated with the species and in the agronomic inputs to those areas. If farming has adapted in a certain way, then it should be able to repeat or reverse the change. There are many options.

  1. Broad scale shifts in the proportions of crops and grass, possibly reversing in part the shift towards grass (Fig. 3).
  2. Continued decrease in the area grown with cereals but concentrating on higher-value products or higher yield, i.e. by taking cereals off the less productive land, a trend already apparent.
  3. Altering the proportions of winter and spring varieties to manipulate the trade offs between yield, inputs and biodiversity.
  4. Replacement of high-input winter cereals with less demanding spring oats in response to challenging conditions- as happened in the 2012-2013 wet years.
  5. Reintroducing wheat varieties for milling, for bread, biscuits and cakes, to reduce dependence on imports, and consequently shifting the aims to nutritional quality and away from bulk.
  6. Growing more ‘mixed grain’ – two or more cereals in the one field – or cereal-legume mixtures such as mashlum that need fewer agronomic inputs [6].
  7. Introducing grain legumes or grass-legume leys into cereal systems to reduce reliance on mineral nitrogen, improve soil and cut GHG emissions.

Now these might not seem like anything markedly out of the ordinary (when surveying the past 150 years) and indeed they are not. Yet cereal farming in many parts of the world would envy these possibilities: there are vast areas in some continents grown with only one main cereal that offers little scope to engineer change.

Moreover, the climate here, on the Atlantic seaboard, will probably not extend to real extremes due to its oceanicity. Complete crop failure caused by weather is still very unlikely here compared to places (for example) like New South Wales and Victoria in Australia where much of the cereal farming is already at risk without irrigation in a ‘normal’ year, and parts of Africa, where land is abandoned, too dry for growing maize.

Cereals fields in stubble, January, Strathspey (@curvedflatlands)

Sources, references

[1] Agricultural Statistics 1912. Volume 1, Part 1. Acreage and livestock returns of Scotland, with a summary for the United Kingdom. Board of Agriculture for Scotland. Some data included for the census years back to 1883. And subsequent yearbooks in this series up to 1978.

[2] Economic Report on Scottish Agriculture: 1980 onwards. Scottish Government – links to all data at Agriculture and Fisheries -Publications.

[3] Symon JA. 1959. Scottish farming: past and present. Edinburgh, London: Oliver and Boyd.

[4] Squire GR. 2017. Defining sustainable limits before and after intensification in a maritime agricultural ecosystem. Ecosystem Health and Sustainability 3/8 (open access, available at https://doi.org/10.1080/20964129.2017.1368873

[5] Cereal and oilseed rape harvest: 2018 final estimates. Scottish Government. Published 12 December 2018. Downloads available from link.

[6] For references to cereal-legume mixtures: Living Field posts Mashlum  – a traditional mix of oats and beans and Mashlum no more! Not yet.

Author/contact: geoff.squire@outlook.com

Funding  The author currently has honorary (unfunded) status at the James Hutton Institute, where he worked for 25 years. A background knowledge of crops, weather and climate was gained previously through funding from the UK Overseas Development Administration and UK Department of the Environment while based at Nottingham University (1970s, 1980s) and more recently through the Scottish Government Strategic Research Programme.

[Page last updated 5 April 2022]

Transitions to a legume-based food and agriculture

A summary with diagrams and photographs of an invited talk at the recent Conference on Advances in Legume Science and Practice organised by the Association of Applied Biologists in Glasgow 21-22 March 2018. Topics at the meeting covered a wide range of experience and disciplines from crop physiology, nutrition, molecular and traditional breeding, symbioses, landscape processes and food security.

Background – summary

Our invited presentation on Transitions to a legume based food and agriculture [1] introduced the aims and approach of the EU TRUE project, notably its central matrix consisting, first, of the quality chain from production through to markets and consumption, and second, sustainability, assessed through  economic, societal and environmental indicators.

The argument runs as follows. (A) Crops and their management alter the flows of energy and matter to various functions in the managed ecosystem. (B) Legume crops and forages have unique roles in channelling energy and matter to crucial functions related to soil quality, the nitrogen economy, pollinators and the production of plant protein. (C) To achieve a balanced and sustainable system, different types of crop, including legumes, need to be grown in planned configurations, whether within fields as mixtures, in  sequences or rotations and in spatial mosaics in the landscape. Practical designs need to consider those configurations that achieve the desired combination of functions.


Fig. 1 Faba beans Vicia faba: young crop, plant in flower, pods and fresh beans, and (small squares l to r) dried beans, flour, shelled split beans and bran.

Increasing legume production and output can be designed and managed in three stages. First, the area grown with existing legume crops such as field bean (Fig. 1)  can be increased with no change to the existing system. Second, the existing system can be modified – but not fundamentally changed – through (for example) mixed cropping of legumes and cereals, rhizobial inoculation of legume seed and  new legume products. Third, the system can be changed completely, with new crops, biotechnology and methods and untried configurations.

The presentation concentrated on  stage 1, but related work in Agroecology at the Hutton is already advancing in stage 2 though experimentation with crop mixtures, rhizobia and new products such as bread, beer and tofu made from beans [2].

Diversifying agriculture using grain and forage legumes

The flows of energy in production systems are investigated through a chain of effect linking interventions, such as agronomic management and choice of crop, through biota, including crops, to ecological processes which in combination satisfy (or not) desired higher level outputs [3].

The main crops in temperate Europe today are managed so that most of the energy is channelled to grain, oilseed or tuber yield (Fig. 2). In consequence,  other channels have been closed, or at least severely restricted, leading to long term declines in farmland wildlife and soil quality. Ultimately, such losses will feed back to limit economic output itself.

Fig. 2 The flow of energy in a winter cereal is concentrated into resource capture by the crop, then formation of yield and product, at the expense of trophic functions and soil.

The solution is to diversify the production systems of the region, in effect opening and regulating channels to other functions.  The diagram in Fig. 3 offers a highly simplified depiction of the wider balance of flows that should be realised in a forage legume.

Fig. 3 The flow of energy in a legume forage is distributed across a range of functions, notably N-fixation and trophic activity, e.g. through invertebrates.

The scope for diversification is being examined in this way for the case study of lowland Scotland. Grain legumes, mainly peas Pisum sativum and beans Vicia faba have been present from the neolithic and bronze periods and a wide range of forage species have been tried and grown over the millennia. Grains and forages are therefore being quantified as to their effect on flows such as represented in Fig. 2 and Fig. 3. Species are then modelling alone and in various spatial and temporal combinations to find optimum states.

Much can be learned from the way legumes and other crops have been grow in in the past, including in-field mixtures, often broadcast from a single ‘bag’ of mixed seed, such as mashlum, and temporal sequences, in some of which the legume and non-legume overlap (Fig. 4). Fields and sequences then combine to give additional properties at the scale of the landscape.

Fig. 4 Examples of crop diversification used traditionally in the region: B is a legume and A another crop (e.g. a cereal, root, oilseed, grass); C is an in-field mixture, such as mashlum, D a blocked, in-field mixture where the crops are separated, Ea a sequence or rotation, Eb a sequence in which some crops overlap in time (e.g. nurse crops and undersowings) and F a spatial configuration in a landscape.

The main problem facing the study was uncertainty in the locations within the region in which legumes appeared historically. However, crop census data, beginning in the mid-1800s is being examined to get the missing information.

First census of the mid-1800s

Legumes became integral to both crop sequences and forage mixtures in the Improvements era after 1700, but while some records suggest legumes occurred  1 in 4 years [4], there is little hard data on the areas grown with them compared with cereals such as oat and barley.

The 1700s and 1800s witnessed a phase of innovation and trialling of both grain and forage legumes, but for reasons that will be explored elsewhere on these pages, most forage legumes dropped out of mainstream usage with the exceptions of clovers and vetches, while grain legumes were reduced to various forms of pea Pisum sativum and bean Vicia faba.

The census of crops and grass in 1854 carried out by the Highland Society, covered most of Scotland and initiated a period of regular crop censuses which have proved invaluable in charting the phasing in and out of different crops. Data on the main crops [5], summarised for each of the old counties of Scotland (current up to to 1890), were transcribed from the 1854 records. Data were available for peas, beans and vetches: as an example, that for vetches is shown in Fig. 5, where the area of the circles, each representing an old county, indicate the relative area occupied by each crop. The circle out to the north-east represents Orkney and Shetland.

Fig. 5 Distribution of the vetches crop in 1854, sown areas represented by circles centred on the old counties of Scotland, superimposed on current administrative areas.

Beans occupied the largest area, followed by vetches and peas which covered similar areas. Most of the crops would have been grown for animal feed. Their combined areas were small, about 5% of that grown with cereals. Other sources specify that mixed forages, such as red clover, ryegrass and plantain, were also grown extensively, but no records are available of their composition and coverage. One of the recurring deficiencies of agricultural census is the classification of mixed forages as ‘grass’.

The distributions of vetches (Fig. 5) and peas were similar, both concentrated in the east and today’s central belt, but extending both south-west and north to Orkney and Shetland. That of beans was more concentrated in the east and centre.

Various crop census after the 1880s continued to show a similar distribution. When peas and beans were distinguished as to whether they were intended for human and animal consumption, those for human occupied a more restricted area in the east of centre.

Grain legume coverage today

Going forward 160 years, IACS data – from the EU’s Integrated Administration and Control System [6] – allows more precise definition of the current area grown with grain legumes.  There is still no data for grass-legume forages which must all classified under one or other of the forms of ‘grass’. Four types of grain legume are reported,  in decreasing order of area – beans for animal consumption, peas for human and for animal consumption, and least, beans for human consumption.

The total areas grown today are even smaller than the combined area of legumes in the 1850s. Maps of legume distribution after 2000 are in preparation. Examples  can be seen at the Living Field post Can we grow more vegetables? and further analysis of changes over time will be given later in these pages. However, the combined areas of the four legume types recorded tend to remain <2% and in some years near 1% of the total cereal acreage.

Low inclusion of legumes in a dynamic production ecosystem

The main conclusion so far is that grain legumes (pulses) were minor components of agriculture in the mid-1800s and have remained minor. Yet many aspects of the the crop and grass production systems in the region have been far from stable. For example, ‘root’ crops, mainly swede and turnip, covered large expanses in the late 1800s, but are relatively minor now, while of the cereals, oat was dominant in the 1800s and early 1900s but  supplanted by barley and now occupies less than 10% of the cereal area.

Recently, other crops have risen to much greater coverage than the legumes, notably winter wheat and oilseed rape in the later part of the 1900s. During all these changes, grain legume areas remained small or decreased.

One of the questions being examined is why legumes have occupied such low acreage in the region and whether and where they could be increased. Investigations of the phenomenon are continuing but one reported contribution is a greater reliance historically on clover and other legume forages for soil fertility.

There seems no particular reason, however, due to limitations of soil or climate, for the restricted area grown with legumes today within the eastern and central ranges shown in Fig. 5. Nor should it be assumed that increases will come only from existing crops. In response to CAP Greening measures, small fields of assorted legumes have appeared in the region.

That in Fig. 6 comprised three species of clover, the well know red Trifolium pratense and white Trifolium repens species, but also an unusual one, crimson clover Trifolium incarnatum which was once tried as a forage at these latitudes. A few plants of sainfoin were seen near the edge of the field, but it was not certain they were sown as part of the mixture.

Fig. 6 Legume forage, mainly of white, red and crimson clover: (top l c’wise) the field, young and older flowering head of crimson clover, sainfoin (image from plant in the Living Field garden) and  plants in an approx 0.5 m width of field (images by curvedflatlands).

Assessment by multi-attribute decision modelling

Opportunities for expanding the area of existing grain legumes are now being examined. It should also be possible to quantify potential savings of mineral nitrogen fertiliser and pesticide as the legume area is increased. The IACS data again provides the wherewithal, allowing us to assess not only which fields contained grain legumes in any year, but also which other crops were grown in the same fields in years before and after the legume. With knowledge of the crops grown in each field, nominal attributes can be assigned based on the pesticide and fertiliser applied to each crop as quantified from national surveys.

Each field can then be given a nominal agronomic ‘intensity’.  The reduction of intensity due to the substitution of an existing crop with a grain legume can then be calculated, as can the trade offs in the areas and output of other crops and products such cereal grain. The four current grain legumes offer plenty of scope for substitution, since some are grown with high-input crops, mainly winter wheat and potato, while others are grown with short-term grass and spring cereals.

Placing a value on each system, and then comparing systems, is facilitated by multi-attribute decision models (MADM) built in DEXi software [7]. A  part of the ‘tree’ structure of the current MADM is shown in Fig. 7. The interventions are shown to the right. They affect in turn the biota and ecosystem processes that determine a higher-level attribute, in this case the N loss in water leaving a field. The full MADM will include the wide range of attributes determining the economic, environmental and societal contributions of production systems.

Fig. 7 Part of a decision tree or multi-attrbute decision model built in DEXi software showing the way interventions combine in effect to influence field-scale attributes, in this case loss of nitrogen (N) in water.

Sites for expansion of legumes are therefore being selected on the basis that (a) they lie within an area, soil and climate in which grain legumes are or have been grown, and (b) they have a balance of crops very close to those fields that already include legumes in the crop sequence.

The aim is to quantify the benefits of legume expansion for the purpose of informing government policy and encouraging food and agriculture to use and grow more legumes. While concentrating on the grains at this stage, there is no reason why the approach cannot be extended to forages such as those in Fig. 8. More widely, the results will form a comprehensive study in the EU TRUE project of an approach to define long term trajectories of legume-based production systems and to extend those trajectories across Europe and farther afield.

Fig. 8 Legume species historically trialled in the region as forages: (top l, c’wise) sainfoin, milk vetch, kidney vetch, tufted vetch and white melilot,all grown in the Living Field garden (images by www.livingfield.co.uk)

Acknowledgement of funding

The main work summarised here and presented at Glasgow was funded as part of the EU TRUE project.  Background knowledge of the maritime production system of lowland Scotland was acquired with funding from Scottish Government (Rural and Environment Science and Analytical Services Division). The authors are based at The James Hutton Institute, Dundee UK.

Sources, references

[1] Squire GR, Iannetta PPM. 2018. Transition paths to sustainable legume production. Aspects of Applied Biology 138, 121-130.  Squire GR, Quesada N, Begg G, Iannetta P. 2018. Transition paths to sustainable legume production. Invited presentation at Advances in Legume Science and Practice, Association of Applied Biologists Glasgow UK, 21-22 March 2018.

[2] Links to bean beer on the Hutton website – Feed the world, help the environment and make great beer. Link to ‘tofu’ make from beans on the Living Field web site – Scofu: the quest for an indigenous Scottish tofu. See also Feel the Pulse.

[3] Squire GR 2017. Defining sustainable limits before and after intensification in a maritime agricultural ecosystem. Ecosystem Health and Sustainability, 3:8, DOI: 10.1080/20964129.2017.1368873

[4] Wight, A. 1778-1784. Present State of Husbandry in Scotland. Extracted from Reports made to the Commissioners of the Annexed Estates, and published by their authority. Edinburgh: William Creesh. Vol I, Vol II, Vol III Part I, Vol III Part II, Vol IV part I, Volume IV Part II. All available online via Google Books. Note from GS: Wight’s journals of his travels through the agricultural regions of Scotland present an unrivalled account by a farmer of the state of agriculture in the Improvements era.

[5] The agricultural census of the Highland Society, 1854, summarised by:  Thorburn T 1855. Diagrams, Agricultural Statistics of Scotland for 1854. London: Effingham Wilson. The Living Field web site has more on Thorburn  at Thorburn’s Diagrams.

[6] Integrated Administration and Control System, IACS on the EU web site.

[7] Decision trees, multi-attribute modelling and DEXi software at Marko Bohanec’s web site DEXI: a programme for Multi-Attribute Decision Making.

Contact: geoff.squire@hutton.ac.uk

 

 

New EU TRUE project holds first meeting

Fantastic news that one of our new EU-funded H2020 project is getting underway. The inaugural meeting was held in Edinburgh, 19-21 April 2017. Around 50 people attended from all EU partners.

The project is coordinated by Pete Iannetta from Agroecology at the Hutton. The aims and methods of the various Workpackages were aired and discussed during two full days. A great feeling among partners of delight that the project would be funded and of looking forward to several years of intense collaborative effort ahead.

Here is the first group photograph.

Project description to follow …..

mixed cropping in Burma

Growing crops as mixtures of different species in the same field was commonplace in Britain during the Improvements era but gradually fell out of favour in the 19oos as single crops became easier to manage and could command a high value on the grain market. ‘Grass seeds’ in the 1700s often meant not just one or more grass species, but a mix of a grass, a clover or several legumes and another species such as ribwort plantain. A cereal (corn) and a nitrogen fixing legume (pea) were also broadcast over the same field, as were mixtures of different cereals.

Mixed cropping is now being reconsidered in northern Europe as a possible means to producing the same with less input of fertiliser and pesticide. In our most recent outing, at the December 2016 meeting of the British Ecological Society, Pete Iannetta talked about the benefits of a barley-pea intercrop grown at the Institute (links at Latest). But for inspiration we can look to other places.

Mixed cropping is still widespread in the tropics, but the reasons for planting different species close together, sometimes in strict spatial patterns, are not always obvious. The scientific tendency is usually to look for a biophysical mechanism behind the pattern. Perhaps the two or more species take resource from different parts of the environment or use the resource more efficiently. Mixed cropping works – the two species together tend to produce 1.1 to 1.3 (110 to 130%) times the equivalent yield of the crops grown alone.

This is a useful but not a great advantage, and it may well be that the plants are grown in mixtures for other reasons also. Sometimes the arrangement might arise simply out of convenience or as a means of lowering the risk of not putting all your eggs (i.e. the few seed of one crop) into one basket (i.e. a small area of soil).

This mixed cropping, named intercropping when the plants are in rows, was frequently observed on a self-funded trip to Burma (Myanmar) during the dry season of 2014. Our interpreter, knowledgeable about local farming, was still not always able to explain what was behind the crop configurations.

Planned intercrops

The biophysical basis of the intercrop was best appreciated for perennial plants such as the pigeon pea Cajanus cajan grown at Bagan with cotton, probably one of the shrubby species, and another plant that had shrivelled to unrecognition in the dryness. The pigeon pea would have fixed and released nitrogen to the soil for the cotton to take up. In some fields, the pea had recently been cut back to stop it using water, whereas the cotton, most likely deep rooting, was in full flower and fruit and using the water and nutrients stored in the ample soil-space between cotton rows.

On the banks of the Irrawaddy, highly regimented rows of groundnut Arachis hypogaea had maize Zea mays sown within every 5th row (image below). The land would have been awash as the river rose in the wet season, when presumably the silty soil, and any nitrogen fixed previously by a legume, would have been picked up in the current and deposited somewhere else.

The crops were therefore growing on nutrient-rich alluvium and soil-stored water. The maize was starting to flower but the groundnut was still in leaf only. It was unlikely that this year’s N fixation by the groundnut would have ‘leaked out’ so early in its growth. Rather, the maize was taking advantage of additional resources, sunlight above ground and residual soil nitrogen from the bordering rows.

Elsewhere, a field of the nitrogen-fixing chickpea Cicer arietinum had been planted with widely spaced rows of sunflower Helianthus annuus.  The sunflower would have benefitted as the maize in the previous example, but it was difficult to see the advantage to the chickpea. Possibly, the farmers wanted some sunflower seed or oil and grew a few plants in what was otherwise a chickpea field.

But why plant in rows …? Rows are generally easier to establish with animal-drawn implements than are small blocks of crop. Intercrop rows also make it more difficult for a farmer to lose a large proportion of one or other species. Repeatedly, patches of a few square metres occurred in the intercropped fields where the crops were stunted or dead, probably due to poor soil or disease. Planting in rows allows both crops to experience the whole field, its good and bad parts.

Unplanned(?) intercrops

In a further set of configurations, the growers appeared not to have planned the mixture. Rather, they took advantage of a situation in which other species emerged with the sown crop.

One such was a small plot of groundnut in which plants of the Chenopodium genus (probably C. album) were growing in a random configuration. Someone nearby, who knew the practice, said that Chenopodium appeared whenever groundnut was grown. It probably emerged from the soil seedbank, stimulated by conditions peculiar to groundnut cultivation. It was encouraged – the ‘weed’ is widely used as a salad vegetable, as it was once in Britain.

Another example was a field of groundnut again, but one that appeared invaded by two or three other species. Chenopodium was there again but also maize and sunflower, and each was located irregularly, not in rows. The groundnut had been sown but the others, including the two crops, had emerged from the soil seedbank. They were ‘volunteer’ weeds, and had been left, not weeded out.

Multiple crops

In Shan agriculture, a mixed crop new to my experience was one of taro Colocasia esculenta, ginger (Zingiberaceae, species uncertain) and chillie, species of Capsicum. It was easy to walk past the field, because the chillies had been harvested and the taro tubers and ginger were mostly invisible underground.  This was an intentional mixed crop. There would have been biological interactions between the three, but perhaps the main advantage was one of getting three crops from the same bit of land in one year – the chillies first, finally the taro.

Repeatedly, crops were seen growing in intended and apparently random configurations. Fruit trees were grown in small orchards, where they usually had an understorey of legumes or mustards. Fruit trees were also dotted around the landscape, enjoying the benefit of nearby fixers and fumigants.

Palms were common, often grown in lines or groves within the general mix of annual cropping. On the high land, fruit and beverage trees were commonly grown in planned (tea and oranges) or semi-random configurations.

Comment

This brief experience, over only a few weeks, introduced the sheer diversity of crops and farming methods here, the ubiquity of legumes, the widespread use of ‘wild’ plants, and the frequent desegregation of the sown and the wild.

Perhaps the lasting impression is one of nitrogen-fixing legumes being among the commonest crops, essential to the mix, whereas in north-west Europe, they have been reduced to minor status.

In some areas, the people had a very advanced understanding of how plants complement each other and together provide human dietary needs, an understanding that has almost lapsed in mainstream farming in north west Europe.

Subsequent pages will deal in more detail with (2) perennial pigeon pea-cotton at Bagan, (3) groundnut-maize by the Irrawaddy and chickpea-sunflower near Mandalay and (4) assorted mixtures which may or may not have any biological advantage.

Sisal plants in the foreground, grown for the fibres in their leaves. The small trees just behind them have been pruned, with one ‘lung’ (a leafy branch) remaining.

Author’s note and further reading

We visited Burma, not in any official capacity, but as ‘tourists’. I had intentionally not read any of the reports from international development agencies before going there, wanting instead to get a first-hand (even if fleeting and random) feel for the soil, people, plants and agriculture. Many of the reports read since have seemed to me to be a bit impersonal, not fully accepting and promoting the great ingenuity and knowledge of the people who live and farm there.

We were more than fortunate to be guided during a crucial part of the visit by Ei Ei Lin (or Lin Latt). Her farming background and natural curiosity introduced us to many hidden wonders of (plant) life in the dry season.

For factual and largely non-judgemental information, the following report offers much on the conditions in Burma’s dry zone:

Improving water management in Myanmar’s Dry zone – for food security, livelihoods and health. 2015. International Water Management Institute (IWMI) 52 pages. doi:10.5337/2015.213. Based on 3 reports published in 2013. http://www.iwmi.cgiar.org/Publications/Other/Reports/PDF/improving-water-management-in-myanmars-dry-zone-for-food-security-livelihoods-and-health.pdf?

Books read during the visit included (and both freely available in bookshops there):

Aung San Suu Kyi. 2010. Letters from Burma. Penguin.

Emma Larkin. 2006. Finding George Orwell in Burma. Penguin Random House.

Pages: Page 1, Page 2, Page 3, Page 4

why so few estimates of nitrogen fixation?

A recent open-access paper Iannetta et al. 2016 gives a comprehensive account of the contribution of legume crops and forages to the nitrogen cycle in temperate agriculture.

Iannetta et al. 2016. A comparative  nitrogen balance and productivity analysis of legume and non-legume supported cropping systems: the potential role of biological nitrogen fixation. Frontiers in Plant Science, 21 November 2016 http://dx.doi.org/10.3389/fpls.2016.01700

Using data from existing field experiments across Europe, nitrogen fixation by legumes was estimated as a residual when other main fluxes of N were accounted for. Annual fixation ranged from 30 to 115 kg/ha of nitrogen. For comparison, the upper figure is a little higher than the fertiliser N given each year to spring cereals.

Why are these figures important? There’s a dearth of estimates or measures of biological N fixation in north temperate agriculture. But while such information is essential for designing sustainable systems, it is not in itself considered to be high-profile (and therefore fundable) science.

Hence the need to add value to existing datasets to get these first estimates. Work is in progress to measure actual fixation rate in arable fields.

Hutton Agroecology group contributions to this paper are as follows. Pete Iannetta developed the overall concept and fronted the paper. Graham Begg designed and led the statistical analysis and modelling. PI, GB and Mark Young carried out the N balance calculations. Geoff Squire and Euan James offered specialist insights.

Page 2 gives some background to the article.

Images: the red clover looked to be part of a natural patch (i.e. not sown) growing locally; the vetch root and nodules were unearthed on a field trip in Attica, Greece during the EU Legume Futures project.

Pages: Page 1, Page 2