Nitrogen contribution from mineralization of vegetable crop residues

Vegetable crop residues can provide variable amounts of nitrogen to the following crop. However, the effects of the typical Quebec winter on this process are unclear. To understand these effects, a study was conducted using three residue management practices on the residues of three vegetable crops: cauliflower, red cabbage and spinach. The residues were: 1) incorporated into the soil in the fall (FI); 2) incorporated into the soil in the spring (SI) or; 3) mulched and deposited on the soil surface in the fall (M). Shortly after the SI, the entire surface of each plot was sown with wheat. Soil samples were taken throughout the experiment for monitoring nitrate status. Tissue analysis was carried out to obtain the nitrogen concentrations of the residues and the wheat. Residues contributed between 10 and 30 % of their initial N content (equivalent in this case to 27 to 77 kg N/ha) to the wheat. Results also showed that handling residues in the fall (FT and M) led to greater risk of nitrate leaching before the next growing season than spring handling of residues did. Fall handling of cauliflower residues and both incorporation treatments for red cabbage residues were the only treatments that contributed significant amounts of nitrogen to the following wheat crop. Spinach residues provided no significant N contribution to the wheat crop.