Study On Effects Of Different Organic Fertilizers On Rice Yield And Soil Characteristics In Double-cropping Rice Area Of Eastern Hunan

Since the 1980s,chemical fertilizers have gradually become irreplaceable in crop production in China,while organic fertilizer have been more and more overlooked.Therefore,there are some negative influences,including soil quality reducing,yield stability reducing and environmental pollution due to long-term utilization of chemical fertilizers.Exploring suitable mode of organic fertilizer application in triple-cropping double-cropping rice area has a great meaning on improving the quality of cultivated land and ensuring stable and increasing yield of double-cropping rice.This study mainly constituted by two-year positioning experiments,and 100%chemical nitrogen fertilizer（T5）was used as control to research the effects of different organic fertilizers(T1:Chinese milk vetch（early rice）/rice straw（late rice）+chemical fertilizer,T2:biological carbon+chemical fertilizer,T3:barnyard manure+chemical fertilizer,T4:rapeseed cake fertilizer+chemical fertilizer.replacing proportion of organic fertilizer to chemical nitrogen fertilizer in T1,T3 and T4 was25%,and application rate of biological carbon in T2 treatment was 15 t hm^-2)on growth and development,yield components,nitrogen utilization efficiency and soil properties of double-cropping rice.The main findings are as follows:（1）In the same nitrogen application level,organic fertilizer replacing partial basal chemical nitrogen fertilizer could delay the attenuation of LAI and decrease of chlorophyll content in the late stage of rice,and lay a foundation for increasing rice yield.Additionally,the yield could be averagely increased by 4.35%and 4.33%in the organic fertilizer treatments.There was a best yield-increasing effect for early rice in Chinese Milk Vetch treatment,averagely increased by 4.86%,and there were better yield-increasing effect for late rice in manure and cake fertilizer treatments,averagely increased by 5.90%and 5.60%,respectively.（2）Organic fertilizer could improve nitrogen content in rice organs,and increasing nitrogen accumulation in the late stage.Both of T2 and T5 treatment had a positive effect in growth,nitrogen content and accumulation at the early stage,but they were lower in late stage of rice.T1,T3 and T4 treatment could improve nitrogen content in late stage of rice,among which T3 and T4 treatment had the highest nitrogen accumulation in early and late rice respectively.（3）Organic fertilizer could increase nitrogen utilization efficiency.Organic fertilizer could improve partial productivity of nitrogen fertilizer,and the average increasing extent was 2.43 kg/kg.There were higher nitrogen dry matter production efficiency and nitrogen grain production efficiency in T2 treatment,and nitrogen transport efficiency was highest in T1 and T4 treatment was highest for early and late rice respectively.The highest nitrogen harvest index was gained in T1 treatment,which was higher than that of T5 by 2.81%.（4）There were no obvious differences in total nutrient content among years,and T1,T3and T4 treatment had nitrogen late release effect.T2 of early rice and T3 of late rice had certain function on improving soil total phosphorus content.All organic fertilizer treatments could increase soil total potassium content,and there showed the more obvious effect in early rice.T3 and T4 treatment could significantly improve soil alkaline nitrogen content,and T2 treatment could significantly improve soil available phosphorus and available potassium.（5）T1,T3 and T4 could increase the soil urease activity in late stage of rice.Soil organic matter content had a stable performance in two years,and which in T2 treatment was significantly higher than that of other treatments.In summary,replacing partial base application chemical nitrogen fertilizer with Chinese milk vetch,cake fertilizer,barnyard manure could ensure increasing and stabilizing yield of double-cropping rice in double-cropping rice area in Eastern Hunan and effectively fertilize soil,and biological carbon had the better improvement effect on soil while it could not showed the significant yield-increasing effect in the short term.