Effects Of Straw-returning On Soil Silicon Species And Nutrient Status Of Rice Plants

Straw-returning to soil is one of the most important approaches of agricultural waste resourceutilization.The rice plants are rich in Si,but there are few studies on the effectiveness and morphological transformation of the soil Si in rice straw returning.In this study,we conducted field and control experiments to investigate the effects of different doses of straw-returning(0 kg hm-2,3000 kg · hm-2,6000 kg · hm-2 and 9000 kg·hm-2)on soil siliconforms and transformation,soil nutrients,soil microbial activity and plant growth and nutrient traits.The results showed that:(1)Straw-returning to field can improve the content of alkali nitrogen and available potassium in soil,but no significant influence on soil available phosphorous content.(2)Straw returning could improve rice biomass accumulation,but had no significant effect on rice biomass.Straw returning could increase panicle number per plant,,grain number,total grain number,grain number per panicle,1000 grain weight and seed setting rate,and reduce the number of empty grains.(3)Different doses of straw-returning did not influence soil acid phosphatase,soil urease and soil sucrose activity.(4)During the experiment,the nitrogen and phosphorus concentration in rice leaves and the stems were reduced by middle straw-returning treatment(6000kg·hm-2);and N and P content in rice leaves and stems were increased firstly and then decreased.Si content in rice leaves and stems was higher at late season than that at early season.(5)The Acid Na acetate–Si content in soil can be improved by straw returning to field,and the releasing speed of Acid Na acetate–Si is: 0 kg·hm-2>3000 kg·hm-2>6000 kg·hm-2>9000 kg·hm-2.The cement pool experiment showed that the Acid Na acetate–Si content in soil at tillering stage was negatively significantly correlated with the amount of straw-returning.The content of the soil H2O2–Si and NH2OH·HC l–Si was significantly different in the early and late season.Soil H2O2–Si content was higher in the early season(≥ 100 mg· kg-1),but lower in the late season(40~100 mg·kg-1),and there was no significant correlation with the amount of straw-returning;Soil N H2OH·HC l–Si content(50~100 mg kg-1)was significantly larger than that in early season(≥150mg·kg-1).The correlation between the content of NH2OH·HC l–Si in soil and the amount of straw returning was opposite,which showed positive correlation in early season field test,and negative correlation of late season cement pool test in tillering stage.Soil Na OH-Sicontent has a very significant positive correlation with the amount of straw returning in the late-season heading period.