Abstract: Effect of straw returning in field scale on soil organic carbon(SOC) and grain yield was studied to explore more reasonable farming management models,which was helpful to provide a theoretical basis for soil cultivation and sustainable agricultural development in Guanzhong Plain.With the actual situation of agricultural production in test area,the trends of SOC,active organic carbon(AC) content and grain yield in different treatments were examined to clear the effect of straw returning through a comprehensive comparison.After the returning of wheat straw to cropland,the summer maize was grown.The result showed that SOC in topsoil(0-40 cm) have been improved in straw application,and that soil AC and carbon pool management index(CPMI) of 0-20 cm soil layer were slightly lowered in high stubble in field,while soil AC and CPMI were increased through smashing the wheat straw into field,which didn't make their mutation change.Subsequently,the result showed that maize stalks were returned to the field in three models,and that,after the wheat growing season,SOC content in the topsoil has increased significantly through the straw returning treatment,and that,through smashing straw into field twice the SOC content can increase by 1.86 g/kg in 0-20 cm soil and 1.69 g/kg in 20-40 cm soil respectively.And also,the returning of crops stalk to the cropland can increase the AC content in the topsoil strikingly-especially,when wheat straw is smashed into the field,the AC content in the topsoil can increase more strikingly,that is,a average AC content can increase by 0.90 g/kg respectively in 0-20 cm and 0.85 g/kg in 20-40 cm soil;And straw returning significantly increased CPMI,especially through smashing straw into field treatments.Under the conditions of climate in Guanzhong Plain,soil organic carbon condition could be improved significantly through returning straw to field scale,especially,the SOC quality can be improved.Therefore,in the short run,smashing and returning the straw to the field can change the SOC more obviously.For there easily appear seasonal drought in the study area,it was useful to improve water use efficiency in maize growth period effectively to ensure the stable or higher yield trough high-stubble of wheat straw in field.It was the optimal model combination of high stubble of wheat with maize straw smashed into field in a whole rotation period for productive and efficient agriculture in this region,which can make a full use of water and heat resources in Guanzhong Plain.

Key words: Guanzhong Plain, Straw returning, Soil organic carbon, C pool management index, Grain yield

CLC Number: 

• S141