Title: Comparison of fertilizer nitrogen efficiency among field crops
Abstract: Abstract (1) Rice, winter wheat, maize, soybean, potato, and sugarbeet were grown with 0, 100, 200, and 300 kg N/ha, and the efficiency of fertilizer-N to produce dry matter of harvesting organs (yield) was analyzed using the following equations: Y=N(plant) • N-E=N(plant) • HI(N)/N%(h.o.), where Y=Yield, N(plant)=N accumulated in plants=Soil-N absorbed+(fertiIizer-N applied)-(absorption percentage of fertilizer-N), N-E=Efficiency of N(plant) for Y, HI(N)= Harvest index of N, and N%(h.o.)=N% of harvesting organ. (2) The yield was generally in the order of sugarbeet, potato > maize, wheat, rice > soybean. (3) The maximum yield was obtained at 100 kg N/ha in sugarbeet and rice, 200 kg N/ ha in wheat, and 300 kg N/ha in maize, potato, and soybean. The protein yield of potato at 200-300 kg N/ha was as high as that of soybean. (4) With the increase of the fertilizer-N level, the N(plant) increased, the absorption percentage decreased, the N-E decreased, the HI(N) decreased, and the N%(h.o.) increased. The magnitude of these increases and decreases differed among the crops. Thus, comparison of the efficiency of fertilizer-N among crops is complex. (5) Sugarbeet absorbed more actively soil-N as well as fertilizer-N, and the N-E was high due to the presence of a low N%(h.o.). However, at above 100 kg N/ha, the N-E decreased remarkably due to the increase of N%(h.o.). (6) Potato responded to fertilizer-N from 0 to 100 kg N/ha better than grain crops due to the high HI(N). The HI(N) remained high and the protein yield was high at high fertilizer-N levels. Key Words: nitrogen responseabsorption percentage of fertilizer nitrogenefficiency of nitrogenharvest index of nitrogen