Department of Plant Sciences

Nitrogen (N) supply is a major factor controlling the yield and quality of vegetables. The purpose of the present study was to determine the effects of different rates of controlled-release N fertilizers (CRFs) and urea applications with cow manure on a) yield (Brassica napa L.), b) nitrate leaching from soil, and c) N2O flux in surface soil. The fertilizers were applied according to the following 6 type-rate combinations: 1) CM-CDU 450 (kg ha-1), 2) LP 450, 3) urea 450, 4) CM-CDU 360, and 5) LP 360, and 6) control (no fertilizer). Yield was significantly higher in theCM-CDU 450 and LP 450 whereas other fertilizer treatments did not show significant differences. The total amounts of leaching nitrate from soils were significantly higher in the urea treatment than in the CM-CDU and LP. Total amount of nitrous oxide (N2O) emission in the urea treatment was highest among the treatments during three cropping seasons. Emission factor (EF) in every treatment ranged from 0.2 to 0.3%.