Is it possible to improve the yield and grain protein concentration of organically-farmed wheat using cover crops or intercrops?

The objective of our work was to investigate innovative sustainable cropping systems to produce regular yields of wheat with a satisfactory grain protein concentration in organic farming systems. Achieving good production levels in stockless French organic farming systems is a major challenge due to strong N limitation. Our approach is mainly based on a better valorisation of the natural nitrogen resources from soil mineralisation and symbiotic fixation of legumes, and not by an increase in the use of organic fertiliser. Two experiments were carried out in southwestern France where winter wheat and durum wheat were grown for their use in human consumption (bread and pasta, respectively). On one hand, cover crops were sown in summer and were incorporated in early November just before the wheat was sown. On the other hand, wheat was cultivated in mixture (intercropping) with a grain legume such as winter pea or fababean. The cover crops were found to be effective in the case of rainy winter years i) because of their role as a nitrate catch crop to mitigate nitrate leaching and ii) because they made it possible to increase the yield and the protein concentration of wheat grains by increasing available N (role of green manure). In the case of intercropping, wheat yield was reduced in comparison to a wheat crop alone, as expected, but the protein concentration was significantly increased and the whole grain yield (wheat + legume) was increased. Thus, in organic farming, intercrops seem to be more effective for enhancing natural nitrogen resources. However, it is still necessary: (i) to optimise the technical sequences of these two farming systems, and; ii) to determine the role of intercrops within rotations and to analyse their effect for both pests and diseases management, which is crucial in organic farming systems

Pea–wheat intercrops in low-input conditions combine high economic performances and low environmental impacts

Intensive agriculture ensures high yields but can cause serious environmental damages. The optimal use of soil and atmospheric sources of nitrogen in cereal–legume mixtures may allow farmers to maintain high production levels and good quality with low external N inputs, and could potentially decrease environmental impacts, particularly through a more efficient energy use. These potential advantages are presented in an overall assessment of cereal–legume systems, accounting for the agronomic, environmental, energetic, and economic performances. Based on a low-input experimental field network including 16 site-years, we found that yields of pea–wheat intercrops (about 4.5 Mg ha−1 whatever the amount of applied fertiliser) were higher than sole pea and close to conventionally managed wheat yields (5.4 Mg ha−1 on average), the intercrop requiring less than half of the nitrogen fertiliser per ton of grain compared to the sole wheat. The land equivalent ratio and a statistical analysis based on the Price\u27s equation showed that the crop mixture was more efficient than sole crops particularly under unfertilised situations. The estimated amount of energy consumed per ton of harvested grains was two to three times higher with conventionally managed wheat than with pea–wheat mixtures (fertilised or not). The intercrops allowed (i) maintaining wheat grain protein concentration and gross margin compared to wheat sole crop and (ii) increased the contribution of N2 fixation to total N accumulation of pea crop in the mixture compared to pea sole crop. They also led to a reduction of (i) pesticide use compared to sole crops and (ii) soil mineral nitrogen after harvest compared to pea sole crop. Our results demonstrate that pea–wheat intercropping is a promising way to produce cereal grains in an efficient, economically sustainable and environmentally friendly way

Mutual legume intercropping for forage production in temperate regions

International audienceCarefully designed intercropping systems can have many advantages in comparison to monocropping such as increased forage yield, enhanced weed control, reduced soil erosion and, in the case of legumes, improved soil fertility due to their symbiosis with nitrogen-fixating bacteria. In addition the use of forage legumes is increasing for the rations of ruminants because legumes supply animal husbandrywith protein-rich diets. Due to lower forage yield from perennial legumes in the first planting year and a critical standing ability of annual forage legumes, farmers tend to establish these crops with a companion crop. The first trials in Serbia studied the role an annual legume in the establishment of a perennial legume. Field pea cultivars with reduced plant height, semi-leafless leaf types and improved lodging tolerance were included together with a pure red clover stand and its mixture with oats as controls. When sown as the companion crop an annual forage legume can provide an economic yield during the perennial forage crop establishment. In average, field pea as a companion crop increases forage annual dry matter yield by 2.56 t ha 1 and reduces weeds in red clover stand by 29%. Another group of trials involved mixtures of autumn-sown cool season, springsown cool season and warm season annual legumes for forage production. Here one plant had good and another poor standing ability and with concurring development stages and similar growth habit. There were economically justified intercrops with Land Equivalent Ratio (LER) values of forage dry matter yield higher than 1, such as winter faba bean with winter common vetch (1.42), spring faba bean with spring grass pea (1.44) and pigeon pea with lablab bean (1.12). The achieved results in the mutual legume intercropping research in Serbia encourage the similar research in the neighbouringWest Balkan Countries and other European temperate regions