Effects Of Various N, P And K Fertilizations On Early Rice Yield In Granitic Sandy 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 granitic sandy 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 fertilization efficiency model of late rice production in the tested soil of 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 fertilization efficiency model of late rice production in Xiangtan County has been gotten, and the application rates of N, P and K fertilizers were obtained as rice yield was maximum by use of computer technique. The N fertilization efficiency functions of 3 experiment sites, Shigu,Qingshanqiao and Jiangshe, were y = 224.00 +27.52 N-1.00N~2,y=229.02+50.81N-2.34N~2 andy=400.53+18.85N-0.83N~2,respectively. The P fertilization efficiency functions of 3 sites, Shigu,Qingshanqiao and Jiangshe, were y=431.91+3.40P-0.17P~2, y=380.18+71.19P-7.57P~2,and y=473.91+25.65P-2.78P~2,respectively. The K fertilization efficiency functions of 3 sites, Shigu,Qingshanqiao and Jiangshe, were y=406.6+13.05K-1.09K~2,y=384.81+50.44K-4.62K~2 and y=438.2+21.55K-1.85K~2,respectively.3. According to the result of "3414" field experiment, the composite fertilization efficiency functions of 3 sites, ZhongLupu,HeKou and WuShi, were also established. The composite fertilization efficiency functions of 3 sites werey=203.87+25.16N-18.65P+44.15K-1.47N~2+0.25P~2-0.7K~2+3.26NP-1.54NK-3.31 NK (Shigu site),y=237.65+7.06N+22.41P+47.74K-1.83N~2-4.35P~2-2.09K~2+4.78NP+1.23NK-5.5 5PK (Qingshanqiao site), andy=371.2+30.22N+7.44P-3.33K-1.00N~2-2.35P~2-2.79K~2-1.63NP+0.24NK+5.23P K (Jiangshe site), respectively.4. The experiment result of different basal fertilizer and topdressing fertilizer application rate showed that the rice grain yield was different when the proportion of basal fertilizer and topdressing fertilizer application were different under the same rate of fertilizer. As the proportion of the base fertilizer and top dressing fertilizer application was 7:3, the grain yield of early rice in Xiangtan County was the maximum.