Influence of split ammonium sulfate on nitrogen availability from N-15-labeled matured soybean as green manure for buckwheat (Fagopyrum esculentum moench)

A poc experiment was conducted at the Experimental Farm of Gifu University to study the effects of N-15-labeled matured soybean as green manure, with and without splitted ammonium sulfate, on the growth and nitrogen (N) nutrition of buckwheat. Crop yield ranged between 0.7 to 2.8g/pot. Applying green manure together with ammonium sulfate split in a ratio of 2 : 1 : I enhanced higher dry matter yield and seed nitrogen content. The crop derived 5.3% N from green manure when applied alone, and between 7.4 to 13.4% N when applied in combination with split ammonium sulfate and basal P2O3 and K2O. Nitrogen from green manure was most efficiently utilized by the crop when green manure was applied together with split ammonium sulphate at the ratio of 2 : 1 : 1. The ''added nitrogen interaction'' (ANI) was positive, indicating that the green manure did not furnish the crop with only N but also caused the effective utilization of soil resources as well.