Soil carbon and nitrogen dynamics under catch crops following winter cereals


In temperate humid climates, catch crops have proven to be a useful tool in the abatement of soil erosion, nutrient leaching and soil organic carbon losses. In Flanders, the environmental policy allows farmers to apply manure after harvest of winter cereals at a rate of 60 kg N ha-1, if a catch crop is sown before the 1st of September (on light textures) or before the 15th of October (on heavy textures). Farmers claim that fertilization stimulates catch crop growth and in that way increases benefits of catch crops. Nevertheless, the question was raised whether fertilizing catch crops would affect N losses during winter. A research project was initiated by the Flemish Land Agency (VLM) to investigate whether the application of pig slurry to catch crops sown after the harvest of winter cereals does not result in higher N losses from the soil between autumn and early spring compared to non-fertilized catch crops.

 

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Field experiments were installed during two consecutive years (2011-2013), each year on 4 locations with different soil textures. After harvest of the winter cereals, pig slurry was applied at rates of 0, ±60 and ±120 kg total N ha-1. On each location 3 to 4 common catch crop species were sown: white mustard (Sinapsis alba), Italian ryegrass (Lolium multiflorum), black oat (Avena strigosa) and a grass-clover mixture (Lolium perenne, Trifolium repens, Trifolium pratense). A bare fallow was included. Catch crops were sown on 2 different dates, 2-4 weeks apart. Soil mineral nitrogen content in the 0-90 cm layer, aboveground dry matter yield and aboveground nitrogen yield were monitored. With the collected data, nitrate leaching and denitrification will be simulated with the EU-rotate_N model, allowing a comparison of N losses between the different treatments.

Researcher: ir. Jeroen De Waele
Period: 2011-2015
Financing body: VLM
Promoter: Prof. dr. ir. Stefaan De Neve