Harvesting cereal-legume associations at an immature stage
The cereal-legume mixtures, also called mixed cropping, are said to be immature when harvested at an early stage with the aim of producing a forage resource (silage, wrapped forage or possibly hay, even grazing).
Cereals can also be grown alone for this same purpose (see page « Harvesting cereals at an immature stage »).
1. Presentation
Characterization of the technique
Details on the technique:
One of the benefits of this technique, beyond the forage it produces, is the early release of plots on which other annual crops can be quickly established, especially in a year of drought. "With associations, you know what you sow, and you observe what you harvest": indeed, one of the main difficulties in managing this type of crops lies in the inability to predict the proportion of the different species in the final mixture, with very strong variability observed between sites and production years. According to several trials, the composition at harvest of a cereal-legume mixture would depend on the availability of mineral nitrogen in the soil, an element that could then be used to target a production goal.
Implementation period
On established crop
Spatial scale of implementation
- Plot
- Farm
Application of the technique to...
All crops:
The technique concerns only cereals and legumes used for forage. The criteria for choosing species for a cereal-legume association are similar to those considered for a mixture intended for grain harvest.
All soil types:
Generalization sometimes difficult
The species chosen for the mixture will vary according to the soil types.
All climatic contexts:
Generalization sometimes difficult
The species chosen for the mixture will vary according to the climatic context.
3. Effects on the sustainability of the cropping system
"Environmental" criteria
Effect on air quality:
Increasing
GHG emissions: DECREASE
Effect on water quality:
Increasing
N.P.: DECREASE
pesticides: DECREASE
Effect on fossil resource consumption:
Decreasing
fossil energy consumption: DECREASE
Other:
No effect (neutral)
The presence of legumes in the mixtures reduces nitrogen needs and allows leaving an interesting nitrogen residue for the following crop. Moreover, the smothering effect of the mixtures helps avoid weed control operations and resistance to pests and diseases is increased thanks to a lower density of each species and a barrier effect between them.
Productivity:
Variable:
Yields are higher and more stable thanks to the complementarity between species. Indeed, the various species present have different development and adaptation characteristics to pedoclimatic conditions, so that depending on the year's conditions, one or the other species will be able to ensure the yield. This yield is generally higher than that of a pure cereal silage (+ 5 to 15%).
Quality of production:
Variable:
Cereal-legume associations, or mixed cropping, generally constitute a balanced (with 30% legumes in the final mixture) and versatile forage. The protein and energy values of these mixtures are higher than those of pure immature cereals, notably due to the presence of legumes in the final forage. However, compared to maize or sorghum silage, the main nutritional limitation of a cereal-legume association silage is its low energy density (about 0.75), coupled with a significant bulk.
These species also provide an interesting supply of minerals, as well as a good content of cellulose (27 to 28%) and thus good fiber content.
Given the variability of the harvested mixture composition, for animal feeding, many authors recommend that farmers analyze their forage mixture at harvest to best adjust the ration.
Soil fertility:
Increasing
The presence of legumes in the mixtures reduces nitrogen needs and allows leaving an interesting nitrogen residue for the following crop. Moreover, varied root systems and a large root biomass help maintain a good soil structure.
Water stress:
Variable
Cereal-legume mixtures deplete soil water reserves less than, for example, a ryegrass undersown crop.
Other agronomic criteria:
Variable
Weed management: increasing
The smothering effect of the mixtures often helps avoid weed control operations.
Pest and disease management: increasing
Resistance to pests and diseases is increased thanks to a lower density of each species and a barrier effect between them.
Previous crop:
These associations are good predecessors for grasslands sown at the end of summer or for a fast-cycle forage crop.
"Economic" criteria
Margin:
Variable
Forages from immature cereal-legume mixtures are produced at lower costs thanks to a simple cropping system, with expenses mainly concentrated on seeds, and thanks to yields generally equivalent to those of maize silage. The economic interest of immature cereals or mixtures depends on the availability of other forage resources that could have been used. Note that harvesting for silage is at the expense of grain harvest and thus part of the farm income.
Peak period:
Increasing
Immature cereals and cereal-legume associations are most frequently harvested in spring or summer, generally from mid-May to mid-June, even early July in some regions. This period can sometimes coincide with haymaking operations, which can cause organizational difficulties for farmers. Moreover, the possible harvest window is relatively short (less than a week to about ten days depending on sources), hence the importance of closely monitoring the crop as the optimal harvest stage approaches.
Annexes
Est complémentaire des leviers
S'applique aux cultures suivantes
Défavorise les bioagresseurs suivants
