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Gros plan de gousse de pois protéagineux.. © INRA, WEBER Jean

Legumes to appease

Legume crops necessary to organic agriculture

The use of legume crops, able to supply nitrogen to the soil, would seem essential to organic agriculture systems. Yet pulses, which can be used in animal feeds, often pose technical problems when sown in pure crops. This is why researchers are investigating legume–grain associations and are developing specialised tools to evaluate these combinations in organic agriculture settings.
 

By Pascale Mollier, translated by Daniel McKinnon
Updated on 02/21/2014
Published on 01/17/2014

Flowers of protein-rich spring yellow pea (‘Respect’). © Jean Weber. © INRA, WEBER Jean
Flowers of protein-rich spring yellow pea (‘Respect’). © Jean Weber © INRA, WEBER Jean

Less nitrogen fertiliser

Although production in Europe has been falling since the 1980s, legume crops merit increased attention owing to their agronomic benefits, particularly their contribution to crop nitrogen nutrition. The “free” supply of nitrogen provided by legume crops in crop rotations is all the more important in organic agriculture systems where nitrogen fertilisers are very costly, and all the more so when the organic system does not include livestock able to supply natural nitrogen fertiliser.

Grain–legume associations: ideas to build on

Despite their value, fodder legumes do not often find a place in grain crop systems. Pulses, frequently used in animal feed, present a number of appreciable technical challenges. For example, the choice pulse crop for France’s climate, peas, can be difficult to grow because yields are affected by limiting factors such as weeds, which often easily out-compete pea crops, issues such as lodging, or insect pests such as the pea weevil.

A promising development is the association of peas grown with grain crops such as wheat (peas and wheat are thus sown and harvested at the same time). Most of the problems identified for pea cultivation can be controlled through this association. In addition, yields are higher, owing to a better use of resources, as is the wheat grain’s protein content, while the need for nitrogen fertiliser is greatly reduced, and residual nitrogen in the soil after harvest is less than for pure pea crops.

Another way to include legume crops in organic farming practices is to use them as intermediate plants (1). To benefit fully from the services intermediate plants can provide, such as supplying nitrogen to the system and controlling weeds, it is better to sow them in spring, once the cash crop is already in place. The legume crop considerably reduces the density of weeds under the wheat and also provides substantial amounts of nitrogen for the next crop. Across a number of trials in the Rhône-Alpes region, the association with legume crops had no negative effect on wheat yields. In one third of cases, however, the wheat protein content was reduced.

See publication on intercropping (PerfCom project, ANR’s Systerra programme, 2009–2012):
INRA Toulouse article on intercropping

Tools to evaluate these new techniques

Adding legume crops to crop rotations has a quite substantial impact on the rotation itself and to the techniques applied to the crops in the rotation. Considerable adjustments are involved and farmers want to have an idea of the kind of performance that can be expected before they commit to any changes. Through the DIM ASTREA programme (2), PERSYST, a predictive assessment tool, was adapted for organic farming in Île-de-France. The tool draws on local knowledge to simulate crop system performance. It has already been used in the region to forecast developments in the most promising systems (see boxed text).

Cultivating industries and markets

The ANR LEGITIMES research programme, which launches in 2014, will work on a wider scale to design and evaluate crop systems and seek ways to reintroduce legume crop cultivation throughout France. The programme will study a number of legume species (pulses, fodder legumes, etc.) and applicable agricultural practices (intercropping, intermediate crops, etc.). The programme will also investigate the new industries and market opportunities needed to rekindle interest in legume crops.

(1) An “intermediate plant” is a species grown in the same plot as a cash crop, which confers a benefit such as protection from disease or pests, or a better use of organic or mineral resources. 
(2) DIM ASTREA: Agriscience, Regional Ecology, and Agrifood (ASTREA) was identified as an Area of Major Interest (DIM) and was recognised as such by the Île de-France regional government on 18 November 2011 for the 2012–2015 period. The programme is designed to encourage research in those thematic areas through doctoral research grant funding over the three-year period, to provide funding to organise science-related events, and to finance investment projects and the purchase of medium-duty equipment (total cost > €200K).

Contact(s)
Scientific contact(s):

Associated Division(s):
Environment and Agronomy
Associated Centre(s):
Versailles-Grignon

Quantitative assessments of crop systems

PERSYST (Agronomic, Economic, and Environmental Performance of Crop Systems) is an open access web application for predicting crop system performance. It can be used to estimate crop yields resulting from the specific crop rotations and management techniques of a given crop system. Environmental and economic indicators specific to the crop system, calculated over a multiyear period, are also used to make the assessment. Initially developed for use with conventional farming practices, PERSYST was adapted for use with organic farming in Île-de-France in 2012.
Contact: laurence.guichard@grignon.inra.fr

In numbers

  • Following a pea crop, wheat yields are 840kg/ha higher than for a wheat crop that follows another wheat crop
  • Plots incorporating pea cultivation  for three years emit 20% less greenhouse gas emissions than a plot without peas
  • Occurrence of eyespot is reduced 54% in a rapeseed/pea/wheat rotation compared to a corn/wheat/wheat rotation