Effects Of Biogas Slurry Application Rate On Rice Yield,Nutrient Uptake And Utilization And Soil Fertility

A field trail was conducted to study effects of biogas slurry on rice yield,nutrient uptake and utilization and soil fertility to obtain the optimal biogas slurry application rates in rice cultivation.The field experiment included five treatments,i.e.chemical fertilizer（CF）,50%chemical fertilizer+50%biogas liquid nitrogen（0.5NBS）,100%biogas liquid nitrogen（1NBS）,150%biogas liquid nitrogen（1.5NBS）,and 200%biogas liquid nitrogen（200%）.The main results and conclusions obtained are as follows:The results showed that rice yield increased with the increase of nitrogen application in the biogas slurry.The maximum yield of rice was reached when nitrogen rate was443.1kg·ha^-1 with the amount of biogas slurry of 939 t·ha^-1.In addition,with the increasing of phosphorus and potassium in biogas slurry application rates,the rice yield was also significantly increased.Compared with CF,other treatments did not significantly affect the seed setting rate of rice.Between biogas slurry treatments,the seed setting rate of 1.5NBS treatment was significantly higher than that of 2NBS treatment.Compared with CF,other treatments did not significantly affect panicle number,grain number and 1000 kernel grain weight.There was a significant correlation between panicle number and yield,but there was no significant correlation between grain number or 1000 kernel grain weight and yield.Application of biogas slurry did not significantly affect the content of N,P and K in rice straw and grain,and did not significantly affect the uptake amount of N,P and K in rice grain.The N,P and K uptake amount of grain in different treatments ranged from120-141kg·ha^-1,63-70kg·ha^-1 and 86-100kg·ha^-1,respectively.The partial factor productivity of N,P and K in different treatments ranged from21.0-39.7 kg·kg^-1,115.5-290.0kg·kg^-1,and 32.8-80.9 kg·kg^-1,respectively.With the increase of biogas slurry dosage,the utilization efficiency of nitrogen,phosphorus and potassium decreased.The apparent nutrient balance showed that the amount of nutrient input increased with the increase of the amount of biogas slurry,and the surplus of nitrogen and phosphorus obviously increased and the deficit of potassium decreased obviously.The application of biogas slurry has no significant effect on soil fertility indicators in0-20 cm and 40-60 cm soil depths,but significantly increased the content of soil organic matter and alkali hydrolysable nitrogen in the subsurface soil（20-40cm）.To sum up,under present experimental conditions,application of biogas slurry has no significant effect on soil fertility indicators.Application of biogas slurry with 939t·ha^-1,that contained nitrogen of 443.1kg·ha^-1,and the optimum yield of rice can be obtained.But high amount of biogas slurry application led to a high surplus of nitrogen and phosphorus,which may have a negative impact on the environment.