Effects Of Various N, P And K Fertilizations On Late Rice Yield In Reddish Clayey Soil Of Xiangtan County, Hunan Province

A field plot experiment with "3414" design was carried out to examine N, P and K fertilization response to late rice on the reddish clayey soil which was developed from granite in Xiangtan County, Hunan Province, and to provide a scientific basis for reasonable fertilization of the local rice production to reduce wasting fertilizers and environmental pollution caused by unreasonable fertilization. The fertilizer response function of late rice production in Xiangtan County was established by use of computer technique based on the experiment result. The main results were as follows:1. Compared the treatment of straight fertilizer with that of not straight fertilizer, the biomass production has increased with applying straight fertilizer under fixing other two elements of N, P and K. In a certain applying rate range, the production has been increased as increasing the straight fertilizer. But when the straight fertilizer reached a certain amount, along with increasing the straight fertilizer, the production decreased. The biomass production of fertilization treatment increased observably compared with non-fertilization treatment.2.According to the results of "3414" field experiment, the fertilizer response function of late rice production in Xiangtan County has been gotten, and the application rates of N, P and K fertilizers as rice yield was maximum were obtained by use of computer technique. The N fertilizer response functions of 3 experiments, ZhongLupu,HeKou and WuShi, were y=337.05+12.26N-0.52N~2,y=348.08+36.81N-1.84N~2 and y=352.8+21.48N-1.03N~2,respectively. As the rice yield of 3 sites reached maximum(Zhong Lupu: 6.20 t/hm~2,He Kou:7.98 t/hm~2 and WuShi: 6.97 t/hm~2),N application rates of 3 sites were 176.85 kg/hm~2, 150.00 kg/hm~2 and 156.45 kg/hm~2,respectively. The P fertilizer response functions of 3 sites, ZhongLupu , HeKou and WuShi, were y=369.38+35.48P-5.83P~2, y=476.96+100.22P-24.51P~2 andy=404.39+53.95P-10.82P~2,and as the rice yield of 3 sites reached maximum(Zhong Lupu: 6.35 t/hm~2,He Kou: 8.69 t/hm~2 and WuShi: 7.07 t/hm~2), P application rates of 3 sites, ZhongLupu, HeKou and WuShi, were 45.60 kg/hm~2,30.60 kg/hm~2 and 37.35 kg/hm~2,respectively.The K fertilizer response functions of 3 sites, ZhongLupu, HeKou and WuShi, were y=388.88+18.20K-1.90K~2,y=410.62+46.12K-3.23K~2 and y=412.73+17.36K-1.36K~2.As and As the rice yield of 3 sites reached maximum(Zhong Lupu: 6.49 t/hm~2.He Kou: 8.63 t/hm~2 and WuShi: 7.02 t/hm~2),N application rates of 3 sites were 71.85 kg/hm~2,107.10 kg/hm~2 and 95.40 kg/hm~2,respectively.3. According to the result of "3414" field experiment, the integrated fertilizer response functions of 3 sites, ZhongLupu, HeKou and WuShi, were also established. The integrated fertilizer response functions of 3 sites werey=316.05+14.23N-1.54P+2.06K-0.53N~2-1.86P~2-0.83K~2+0.10NP-0.27NK +3.54PK (ZhongLupu site),y=306.24+34.64N+4.05P-21.07K-1.28N~2-1.39P~2+0.20K~2-4.79NP+l .20N -K+10.44PK (HeKou site), andy=323.99+22.19N-34.18P+3.04K-0.69N~2-2.57P~2-0.24K~2+1.29NP-1.38N--K+7.87PK (WuShi site), respectively.