| The rice-wheat rotation is the main producing mode of grain crops in China.It occupies nearly 13 million hm2 area in China and its total output accounts for more than 1/4 of the national grain output.However,with the rapid development of society which leads to that the area of agricultural arable land has decreased while the population has continued to increase,Chinese food security issues gradually become more prominent.Raising the grain yield per acre land of our country is one of the important means to ensure food security.To ensure the normal growth of crops and grain production during the process of planting agricultural crops,a certain amount of phosphate fertilizer is required.However,because the phosphate fertilizer in the soil is often fixed,the efficiency of phosphate fertilizer utilization is in a low level.This study focuses on the key problems in rice and wheat rotation,such as low phosphorus nutrient utilization rate,exploring the effects of different fertilization measures on the production of rice and wheat as well as the phosphorus components in soil.By this,it can achieve a common development in between the improvement of phosphate fertilizer using rate and the efficient utilization of phosphorus element,which provides some practical significances on regulating the efficient use of phosphorus element in soil and reducing the environmental pollution of phosphate fertilizer.This experiment was conducted from 2018 to 2019 in the long-term test fields that belong to Liyang Technology Research Demonstration Base of Nanjing Agricultural University,located in Qianjiaxu Village,Nandu Town,Liyang City,Jiangsu Province,and Rugao Agricultural Science Research Institute,located in Rugao City,Jiangsu Province.These two areas,in Liyang City and Rugao City,are both typical rice-wheat rotation ecosystems.The fertilization treatments in the two test sites are:No Phosphorus Treatment(NK),Chemical Fertilizer Optimization Fertilizer(OPT),20%Reduction in Phosphorus by Pig Manure Based on Optimized Fertilization 20%Treatment(HERP20%PMSP20%).20%Replacement of Phosphorus by Pig Manure Based on Optimized Fertilizer Treatment(PM SP20%).The planting system is rice-wheat rotation,twice cropping a year.This experiment will analyze the following items that will be influenced by different fertilization measuresthe quantity of crop yield and its components,the efficiency of phosphorus utilization,the results of crop absorbing and utilizing the phosphorus nutrient,the conversion of the phosphorus element in soil,and the phosphorus combination in soil.In the meanwhile,it will also provide a theoretical basis for efficient use of phosphorus as well as the high and stable crop yield.The main results of this experiment are as follows:1.Application of phosphate fertilizer can increase rice and wheat yield and also increase utilization rate of phosphate fertilizer.In the rice season,the yield of it can be increased mainly by increasing the number of tillers,which can reach to 4.9%～15.8%;while on wheat,the yield of it can be increased by increasing the number of spikes and the grain number per spike,which can reach to 8.99%～17.5%.Application of the Phosphorus fertilizer can increase 22.5%一 53.4%of the annual phosphorus accumulation of rice and wheat.After applying organic fertilizer,it significantly improves the agronomic utilization rate of phosphorus fertilizer,the partial productivity of phosphate fertilizer and the absorption utilization rate of phosphate fertilizer.And this is more conducive for crops in phosphorus absorption and utilization,and improves the utilization rate of phosphate fertilizer.2.The phosphorus activation coefficient of the soil increases after the phosphorus fertilizer being used,it can increase by 9.40%一 35.4%in the rice season;it can increase by 27.4%～87.7%in the wheat season.However,it is the most effective when the organic fertilizer is used.Applying the organic fertilizer can significantly increase the microbial carbon and nitrogen content in the soil in the rice and wheat season,respectively increased by 30.5%～127%and 27.1%～151%.After applying organic fertilizer,the activity of microbial biomass phosphorus and acid-base phosphatase in the soil is significantly improved,promoting the conversion of phosphorus.3.After applying the phosphorus fertilizer,with the input of phosphorus,the total inorganic phosphorus content in the phosphorus combination can be increased by 44.1%～75.4%in the rice season;and 37.8%～73.6%in the wheat season.The total organic phosphorus content can be increased by 14%～57.7%in the rice,and 9.63%～30.9%in the wheat.It can be found that the application of organic fertilizer can increase the proportion of active phosphorus reservoirs,Resin-Pi and NaHCO3-Pi,in the phosphorus combination,while reduce the proportion of residual phosphorus reservoirs.It shows that the application of organic fertilizer can improve the effectiveness of soil phosphorus.4.With the application of phosphate fertilizer,it shows that there are some phosphorus surpluses in the soil.By the OPT treatment,the surplus value gets the highest level,which is average in 101.1 kg/hm2.Applying the organic fertilizer can reduce the surplus value,among which the RP-PMSP treatment makes the surplus get to the lowest level,average in 39.25 kg/hm2.Application of organic fertilizer can increase phosphorus absorption of rice-wheat rotation crops and maintain annual phosphorus balance.In summary,application of the phosphate fertilizer,especially organic fertilizer replacement treatment can optimize the composition of crop yield as well as the phosphorus accumulation and distribution.It also cultivates the soil better,improving the utilization of phosphorus fertilizer and the availability of phosphorus.Eventually,the goal of stabilizing and increasing crops production can be achieved,which provides a theoretical basis for the high and stable yield of rice-wheat rotation crops and the rational utilization of the phosphate fertilizer resources. |
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