| Silicon(Si)is an essential nutrient for the growth and development of rice.However,Si deficiency has become an important factor limiting the high yield of rice in southern China.Therefore,it is particularly important to improve the content of soil available Si.At present,the organic amendment is considered to be an economical and effective practice to improve soil Si level.In this study,the effects of organic amendments(straw,straw biochar,and milk vetch)on the transformation and availability of soil silicon,soil chemical properties,rice yield and silicon nutrient absorption were investigated.Two soils were used in this study,including sandy soil and paddy soil.Soil incubation experiment,pot experiment,and field experiment were conducted.The main results are as follows:(1)Effects of returning organic amendments to fields on soil chemical properties:The results of indoor soil culture tests showed that: after straw and biochar were added,soil p H value,EC value and SOC content increased significantly compared with CK,and p H value increased by 0.17 to 1.57 units.Straw had a better effect on SOC than biochar,while biochar had a better effect on EC.In field experiments,organic material returning(MSF and SF)significantly increased soil p H value by 0.10 and 0.09 units,respectively,under constant nutrient conditions.Meanwhile,MSF and SF treatments significantly increased the contents of soil organic matter and available nutrients,and the increase of organic matter was 13.20%-14.63%,and the content of soil available nutrients was the highest in SF treatment.In the pot experiment,straw and biochar significantly increased soil p H when the same nutrients were added,but the effect of straw and biochar on soil nutrients was not obvious compared with the single application of chemical fertilizer.However,straw and biochar input had more obvious regulation on soil phosphorus and potassium.(2)Effect of returning organic amendments on soil silicon fractions: In the soil culture experiment,the amount of available silicon pool in soil was proportional to the amount of straw and biochar,and the amount of available silicon in biochar treatment was higher at the same silicon input level.The contents of mobile silicon,adsorbed silicon and organic bonded silicon in soil and their proportion in amorphous silicon increased with the addition of straw and biochar,and their contents increased by6.17%-258%,3.6%-510% and 19.85%-110%,respectively,and biochar treatment had the best effect.There was a significant positive correlation between the amount of amorphous silicon in soil and the amount of straw,and a negative correlation between the amount of biochar.The results of field and pot experiments showed that returning organic materials to field increased the content of adsorbed silicon and amorphous silicon in soil.In the field test,under the condition of equal nutrients,MSF and SF treatments increased the adsorbed silicon by 21.41% and 21.01% compared with F treatment.In the pot experiment,compared with CK treatment,the increase of soil adsorption silicon of early rice and middle rice was 20.05%-31.64% and 30.67%-57.76%,respectively.The results of correlation analysis and path analysis showed that soil movable dynamic silicon could be used as effective silicon source,while soil adsorbed silicon,organic bonded silicon,(hydrogen)oxide bonded silicon and biological amorphous silicon could be used as slow effect silicon source.(3)Effects of organic amendments returning on rice yield and silicon absorption:the yield of potted early rice and field late rice under organic amendments returning was basically the same as that under chemical fertilizer alone,but the yield of potted medium rice was significantly lower than that under chemical fertilizer alone.Returning organic amendments to the field increased the content of silicon in rice shoots and promoted the absorption of silicon in rice.Correlation analysis showed that there was a significant positive correlation between the amount of silicon absorbed by rice and the contents of movable dynamic silicon,adsorbed silicon,organic bonded silicon,soil(hydrogen)oxide bonded silicon and amorphous silicon in soil,indicating that the absorption of silicon by rice was closely related to the transformation of soil silicon fractions.In summary,organic amendments can effectively increase soil p H value,soil organic matter and nutrient content,improve soil acidic environment,and maintain soil fertility.The addition of organic amendments can significantly increase the soil mobile Si and adsorption Si content,which is more effective for enhancing the soil available Si pool,and at the same time,it can also increase the content of soil organic bounded Si and amorphous Si,which is conducive to increasing the slow-acting silicon pool of the soil. |
