| Songnen Plain is located in the provinces of Heilongjiang and Jilin.It is the main producing area of maize and soybean in China.In 2015,the maize production of the two provinces was 35.441 million tons and 28.057 million tons respectively,and the maize straw amount reached 42.53 million tons and 33.668 million tons respectively.The soybean production was 4.373 million tons and 0.486 million tons respectively,and the amount of soybean straw was 8.744 million tons and 0.972 million tons respectively.Excess straw resources have caused a large amount of straw to be burned in the open,causing serious pollution to the environment.Straw returning can not only solve the problem of environmental pollution caused by incineration of straw,but also return various nutrients contained in straw directly to the soil to maintain soil fertility.At the same time,returning straw also affects the phosphorus absorption and yield of the crop.In the soil and climate conditions of the farmland in the central part of the Songnen Plain,the nylon mesh bag method was used to study the one-year and multi-year decomposing rules and nutrient release characteristics of soybean and maize straw.Soybean and maize were used as the research object.There are three methods of returning,straw was not returning,returning straw directly and straw burning returing.Simultaneously,two levels of phosphorus application,no application of phosphate fertilizer and normal application of phosphorus,were set to study the effect of straw returning on phosphorus absorption and yield of soybean and maize.The results showed that:The maize and soybean decomposition rate of returning straws were mainly concentrated in the first three years of returning.The rate of decomposing in the first year was the fastest,and the total decomposing rate of maize and soybean straws reached 57.39% to 60.63% and 64.13% to 65.04% in the first year.The accumulated decomposition rate for the three years was 91.70% and 92.67%.In the first year of returning straw,it was the fastest to decompose from May to September.The release of nutrients from returning maize and soybean straw was mainly concentrated in the first three years of field return,and the release rate was K>P>C>N.First year after returning to field,the release rates of K,P,C,and N from maize and soybean straw were 95.06% and 89.72%,63.01% and 72.42%,62.44% and 64.29%,58.92% and 49.58%,respectively.After three years of decomposition,the accumulative release rates of K,P,C,and N from maize and soybean straw were 99.10% and 99.05%,92.03% and 91.80%,90.96% and 90.70%,89.43%and 87.40%.The hemicellulosic decomposition rate of maize straw returned to the field was the fastest,cellulose was the second,and lignin was the slowest.The rate of cellulose decomposition in soybean straw was the fastest,followed by hemicellulose and slowest in lignin.In the first year of returning straw,the decomposition rates of cellulose,hemicellulose,and lignin in maize and soybean straw were 62.32% and 71.79%,71.40% and 69.67%,33.16% and 41.66%.After four years of decomposition,the decomposition rates of cellulose,hemicellulose,and lignin in maize and soybean straw reached 92.94% and 97.41%,97.71% and 95.77%,87.21% and 91.43%.Under the condition of applying phosphate fertilizer and not applying phosphate fertilizer,the phosphorus content in the soybean and maize plant during the growth period of the straw is expressed as the application of the phosphorus fertilizer can increase the phosphorus content of the plant.There was no significant difference in the impact of straw return on soybean yield under both phosphorus and no phosphate fertilizer application.The effect of straw return on maize yield was significantly different under the conditions of phosphorus application,but the application of phosphate fertilizer could increase the yield of plant. |
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