The Nutrient Releasing Regularity Of Crop Stalks Under Different Conditions

Crop stalk is a valuable renewable organic resources, it can improve and ameliorate soil fertility and increase crop yields after stalk returning. Stalk returning has already become the most direct and effective way to improve soil fertility. The experiment was carried out in the Agricultural technology promotion center of Shuangcheng and box planted field of Heilongjiang Academy of Agricultural Sciences on May26,2010and June8,2011. Net bag method was used to determine decomposition rate, nutrient characteristics of crop stalks, and regulation organic matter under different incorporation method into the field. At the same time determination the impact on soil microbial biomass carbon and nitrogen, and self-toxicity and his sense of effect on the after-cropping. So that we can find provide the basis for the rational application of straw and soil improvement. Based on the data analysis, the result of the study indicated that:1. The results showed that after120days, biomass decomposition rate of maize stalks in different depths were the depth of10cm> depth of5cm> depth of2cm, organic carbon decomposition rate of the three treatments showed the same trend, and gradually increased with time passing. Organic carbon decomposition rate of depth10cm,5cm and2cm were about60%after120days, respectively. P and K decomposition rate were faster than N. and the releasing rate of N, P and K were63.3%～65.8%,86.9%～90.5%,82.8%～90.7%.respectively: while the depth of10cm and depth of5cm significantly faster than the depth of2cm in the releasing of K, the depth of10cm is more suitable for maize stalks decomposition.2. Decomposition of maize stalk and soybean stalk under different lengths after two years, biomass decomposition rate of the first year was about55%, biomass decomposition rate of maize stalk was more than soybean stalk; biomass decomposition rate was77%～88%in the second year, soybean stalk was more than maize stalk. Decomposition of maize stalk in length2cm was the fastest, soybean stalk was in length6cm. Organic carbon decomposition of maize stalk and soybean stalk were about88%under different lengths, the releasing rate of maize stalks were2cm>6cm>10cm, soybean stalks were6cm>10cm>2cm. N release rate of stalks returning into soil were63%～80%under different lengths. P and K release rate were about90%indicated that the release rate of stalk returning did not significantly difference between different lengths. So stalk returning in length2cm recommended was better than other length and soybean stalk was6cm in agricultural production.3. Biomass decomposition rate of maize stems and leaves were53.5%、64.1%respectively after120days. N release rate of stems were27.7%higher than leaves; Organic carbon decomposition rate of stems was12.2%lower than leaves. Microbial carbon and nitrogen content of maize leaves surrounding soil were higher than the stem treatment, and that was the most obvious within early30days.4. The decomposition rate of maize stalk biomass were been enhanced adjust the C/N; N release rate of stalk were lower than the contrast adjust the C/N, P release rate and organic carbon decomposition of stalk were higher than the contrast. Adjust the C/N, microbial biomass carbon content increased significantly from stalk surrounding soil.5. Mineralization rate and humification coefficient of the maize stalks by Jenny model can predict the dynamic and balance of soil organic matter after stalk returned. the result of the study indicated that:organic matter content of soil can be maintained at around3.5%if continuous application of stalk for10years, annual application of6.2t/hm2maize stalk and5.7t/hm2soybean stalk. These may regulate organic matter content of soil, and determine the nature and quantitative target of soil fertility.6. Maize stalks self-toxicity and his sense of effect indicated that:in the absence of exogenous N supply conditions, stalk decomposition restrained maize growth after30days and60days. However, decomposition of stalk under different concentrations restrained more and more weakened on maize growth with time passed. His sense of effect of maize stalks indicated that, the low concentrations promoted obviously to wheat seedling height, and concentrations increase promoted more and more weakened.