Effect of lucerne on nitrate-N accumulation in a long-term maize-wheat double cropping experiment

Yield and soil nitrate-N were measured in a long-term nutrient supply exper iment established in Kompolt, Hungary in 1961. Five of the 12 treatments we re selected (control, two levels of NPK supply, and addition of FYM or crop residues) in a traditional maize-winter wheat double cropping system and i n addition a four-year lucerne sequence was grown at the same time. The obj ective of the study was to examine the after-effect of lucerne on a winter wheath-maize double cropping system. The results suggest that lucerne had a significant effect on the soil nitrate-N content in the 0-300 cm layer. Th e nutrient supply modified this effect. The peak of nitrate-N accumulation occured at a depth of 150 cm in both sequences. At the highest (176 kp N/ha ) treatment level in the rotation without lucerne the maximum amount of nit rate-N was less than 100 kg N/ha, while it reached more than 200 kg N/ha wi th lucerne between a depth of 100-150 cm. The yield of winter wheat showed a significant difference only in the contr ol after lucerne.