Establishing Valuable Cover Crops (Catch Crops or Double Cropping)
In agriculture, a catch crop is an intermediate crop or a cover crop, with rapid growth, cultivated between two successive main annual crops during the more or less long so-called intercropping period.
It can be sown between a spring harvest and the autumn planting or sowing of certain crops.
Description and differences
A catch crop can be distinguished from other intermediate crops by a goal of production valorization. Within a crop rotation, the catch crop thus optimizes the use of available agricultural land. They can serve various purposes depending on the cropping system; the three examples below cover the main uses.
In arable cropping systems
Crops are selected for their short cycle (soybean, sunflower, maize, buckwheat, sorghum...) for grain harvest. They are planted between an early harvest crop (winter barley, pea, garlic, rapeseed...) and a winter (wheat, barley...) or spring (maize...) crop.
Example of implementation
Sowing of Sunflower (variety "100-day") in the days following the harvest of a Winter Barley. Removal of residues from the previous crop is preferred to avoid hindering emergence. Soil work is limited to 1-2 passes without deep tillage to avoid drying the surface horizon (but if the surface horizon is already dry at harvest, a plough followed by rolling after sowing can give better results). In the absence of rainfall in the days following sowing, irrigation is necessary to ensure rapid emergence. Generally, 2 to 4 irrigations are needed thereafter. Harvest can take place from mid-October, before planting a winter cereal. Yield potential is around 20 q/ha.
In crop-livestock systems
Preferably, crops with forage valorization are sown, harvested as silage, wrapped, or even mowed for green feeding (Italian ryegrass, millet, possibly mixed with clover, mixed crops …), or grazed (forage rapeseed, forage cabbage...).
Sowing can then take place during winter between two spring crops (Italian ryegrass between two maize crops...).
In organic farming, with often low nitrogen residues at harvest, legumes for forage purposes can be sown as catch crops (vetch, alfalfa, clover...).
In the case of forage crops or energy valorization, the goal of the catch crop is to produce a large amount of biomass in a short time to be valorized in various forms (grain harvest, forage, energy…). The choice of crop will therefore favor species with high biomass production.
In systems with methanization
In this specific case, the focus is on sowing CIVEs (Intermediate Crops for Energy Purposes). The whole plant is then harvested to feed the methanizer. Thanks to the fermentation of CIVEs, the methanizer can produce biogas, used as a source of heat or electricity. The methanizer also produces digestate which can be used to fertilize crops.
Two types of CIVEs are distinguished :
- The summer CIVEs (sorghum, maize, sunflower, associated or not with legumes), sown mainly between mid-June and late July to benefit from warm temperatures and longer days. Yields of these crops are very variable as their growth depends on summer rainfall.
- The winter CIVEs (mixtures based on grasses (e.g., rye, oat, triticale) and sometimes legumes) sown around October. These crops benefit from a long (over six months) and wet growing period.
Application of the technique to...
Implementation period : During the intercrop period.
Spatial scale of implementation : Plot
All crops : Generalization sometimes difficult
For grain harvest, only short-cycle crops (sunflower "100-day", soybean 000 or 0000 from 2013, early varieties of maize or sorghum or spring pea, buckwheat) are suitable for catch cropping.
All soil types : Generalization sometimes difficult
Except for hydromorphic soils which may make a harvest in October delicate in the case of grain valorization, the technique can be generalized to all soil types. Access to irrigation may be necessary to secure emergence and yield.
All climatic contexts : Generalization sometimes difficult
Crops sown as catch crops for grain valorization still require a minimum temperature sum to reach maturity (1,300 to 1,400 °C base 6 °C for a catch crop sunflower, 1420°C base 6°C for a soybean 000). This technique requires a frequent climatic analysis to determine how often it achieves the expected results, and the latest sowing date for catch crops. Catch cropping should be considered as an opportunity strategy to be implemented when the year's climatic conditions allow it (early harvest of the previous crop, for example). Catch cropping of forage crops can be considered in a wider range of climatic contexts.
Regulations
Regulatory influence
Warning: sowing a catch crop must be declared on plain paper to the DDT.
For more information on CAP rules and nitrate directive for catch crops: Sheet on CIPAN/Catch cover crops from the Chamber of Agriculture of Brittany.
Environmental criteria
Pollutant transfer to water (N, P, pesticides ...): Decrease.
The presence of a cover crop on the plot throughout the year limits pollutant transfer occurring between two main crops. However, sowing a catch crop may require additional herbicide applications to manage regrowth of the previous crop.
Pollutant transfer to air (N, P, pesticides ...): No knowledge on this impact.
Fossil energy consumption: Increase.
Even if soil work is limited, interventions related to sowing the catch crop involve fuel consumption. Moreover, some crops may require drying (sunflower, maize) and irrigation.
GHG emissions: No knowledge on impact.
Biomass production by the catch crop contributes to increasing the amount of fixed carbon, and reduced nitrate leaching decreases indirect N2O emissions. However, GHG emissions related to fuel consumption increase, especially for crops requiring drying and/or irrigation.
Agronomic criteria
Productivity : Increasing.
Grain-harvested crops have a reduced yield potential as catch crops due to a shorter cycle. The yield of main crops may also be affected if early varieties are deliberately chosen to extend the intercrop period. However, sowing catch crops in addition to main crops leads to a global increase in system productivity.
Soil fertility : Variable.
Sowing catch crops involves mineral element uptake which may reduce availability for the following crop.
Water stress : Variable.
Sowing catch crops involves water uptake which may reduce availability for the following crop.
Soil structure preservation : Variable.
In case of late harvest under poor conditions of the catch crop, risks of soil structure degradation exist. Conversely, in hydromorphic soil, a winter catch crop that extracts water can improve spring workability for sowing a spring crop.
Economic criteria
Operating costs : Increasing.
Sowing a catch crop involves costs related to seed purchase, phytosanitary products, irrigation, and possibly drying (200-300 €/ha in the case of a catch crop sunflower).
Mechanization costs : Increasing.
Sowing a catch crop generally involves more and costlier passes (soil work, sowing, harvest...) than leaving the soil bare during the intercrop period or sowing an unharvested intermediate crop.
Margin : Variable.
The margin of the catch crop strongly depends on the context of selling and input purchase prices, but it is lower than that of main crops due to reduced yield potential. However, it generally remains positive in adapted regions and contributes to improving the overall system margin.
Fuel consumption: Increase
Sowing, monitoring, and harvesting a catch crop involves higher fuel consumption than false seedbed preparation, sowing, and destruction of an unharvested intermediate crop.
Social criteria
Working time : Increasing.
The work rate of sowing and harvesting interventions for a catch crop is lower than that of stubble cultivation, sowing/destruction of unharvested intermediate crops.
Observation time : Increasing.
Sowing a catch crop requires additional observation time for irrigation management, essential in most situations.
For further information
- Frédéric Pagès produces two crops per year
- -Réussir arable farming n°246, p74-75, Press article, 2011
- Catch crop sunflower - Anticipate and sow early to succeed
- -CETIOM, Website, 2011
- Sunflower and soybean - Successfully sowing a catch crop
- -Lecomte V. (CETIOM) Agricultural Perspectives n°357, p93-95, Press article, 2009
- Three crops in two years with an additional sunflower, sorghum or maize
- -Réussir arable farming n°217, p40, Press article, 2008
Appendices
- Redirect Modèle:Pages liées
See the following crops :
