Best practice for the cultivation of grain legumes

One grain legume is not like another! Lupins have other requirements in addition to the pH-value, soil type and soil conditions and other site-specific factors as peas or field beans. Soybeans, for example need a certain heat summation for good growth, maturation and on-time harvest. All these factors impact successful legume cultivation and must be strictly observed when choosing a grain legume for cultivation.

The recommendation for peas was extended to 9-10 years due to project results. Mainly because of the soil-borne pathogens such as pathogens Ascochyta pisi, Mycosphaerella pinodes and Phoma medicaginis or Fusarium that require long cultivation breaks. In addition there are interactions with other legumes, such as red clover or alfalfa in the crop rotation. To study the "soil or legumes fatigue" we recommend the differential diagnostic test system as a practical tool which can help to avoid high-risk plots - so far the system has been tested primarily for peas.

To achieve this goal, homogeneous crop stands must be established. This starts with an intensive stubble cultivation, which reduces weed infestation or, with a site-adapted seed bed preparation in combination with well-dried and trafficable soils. The specific sowing densities of grain legumes have to be taken into account, thousand kernel weight and germination rate, as well as the corresponding sowing depths and sowing in a sufficiently warmed soil so that seeds can germinate quickly.

Homogeneous crop stands have a better ability to suppress weeds, they also increase the efficiency of direct measures for weed control (harrowing, hoeing). An intercropping of grain legumes and cereals or, depending on the grain legume, also with other crops such as camelina, guarantees crop stands with a high weed suppressive effects. Intercropping permits the use of reduced tillage systems, precisely because mixed cultivation suppresses weeds in an excellent way.

For peas and vetches the mixed partner ‘cereal’ increases the lodging resistance of the grain legumes. The intercropped stands can be safely harvested.

Even the attack of the grain legumes by aphids is significantly reduced in intercropped stands. We were able to demonstrate this for the cultivation of intercropped winter peas with triticale.

At this time, normal-leafed, long winter forms of peas often show sufficient winter hardiness. However, these require an intercropping partner with a good supporting effect such as triticale or wheat. Winter forms of peas are characterized by higher yields and N2-fixing rates compared to semi-leafless winter and spring peas.

When soil analysis shows a need for K-, P- and Mg-fertilizer, it is recommended to apply the fertilizer directly to the grain legumes, except of soybeans. Attention should also be paid to an adequate supply of sulfur, because sulfur is needed for N2-fixation as well as for the synthesis of amino acids. In Organic Farming only the permitted fertilizers can be used.

The various grain legumes have different pH-value requirements; this must be taken into account in the choice of the crop. If the pH-level is too low, the nitrogen-fixing soil bacteria are hindered - the nitrogen fixation rate decreased. Therefore, the pH values should be in the optimal range depending on the site and the soil types. If is nonetheless necessary to lime the soil, this can be done directly to the legume or after harvest of preceding crop.

If soils are supplied with adequate organic matter, the soil structure is improved, as well as the water-holding capacity – here the grain legumes will benefit as they all require a steady water supply. A good soil structure also promotes legume development, in particular for peas. Examples of positive effects of a targeted supply of organic fertilizers: yard waste compost significantly reduces the pressure of pathogens; the application of chopped green material reduces weed infestation in the cultivation of the coarse-grained grain legumes.