Main research question/goal
Can pig slurry be applied on catch crops sown in cereal stubble without increasing the risk of nitrate leaching in comparison with cereal stubble without slurry application and without a catch crop? What is the optimal manure dose on cereal stubble to increase the retention of nitrogen by catch crops during winter, and thus to reduce nitrate leaching? Are there effects on the soil organic carbon level and on the N supply by the catch crop residues incorporated in the soil?Research approach
The research is based on field trials on 4 locations with a range of soil textures (sand, sandy loam, loam and clay). The field are on the stubble of triticale, winter wheat or winter barley. Pig slurry is applied at doses of 0, 60 en 120 kg N/ha (total nitrogen). On each location 3 common catch crop species (white mustard, Italian ryegrass, black oats) are sown on two dates, in addition to a treatment without catch crops. On 3 locations a grass-clover mixture is sown as well, which is relevant to organic agriculture. Field measurements are extended with carbon and nitrogen mineralisation trials in the lab. The collected data are used for modelling the carbon and nitrogen dynamics in crop rotations with cereals.Relevance/Valorisation
The use of catch crops is an agro-environmental measure aimed at reducing the nitrogen losses after the preceding crops. Applying additional fertilizer on the grain stubble can be maintained in the manure decree if nitrogen losses by leaching are lower for the catch crop than for the unfertilized stubble without a catch crop. Furthermore, N losses should not be significantly higher than for soils with a catch crop on the stubble without additional fertilizer application. In case of higher catch crop biomass we expect a higher input of organic matter to the soil. Maintaining or increasing the soil organic matter levels is a major concern because of the strict fertilizer regulations in Flanders.