Does the Biennial Straw Return Have an Identical Characteristic of Soil Organic Carbon Sequestration as the Annual? A Case Study of Cornfield in Northeast China

Abstract

Straw return is a common cultivation to improve soil fertility and realize sustainable agricultural development. However, the effect of returning interval on the corn straw humification process in northeast China is little known. In this study, a four-year field trial was conducted to investigate the characteristics of soil carbon sequestration under the annual deep straw return (T1), the biennial deep straw return (T2), and the non-straw return (T3) in Jilin Province, China. In order to precisely evaluate the soil organic carbon density (SOCD), each soil horizon was divided differently according to the actual situation, rather than a fixed thickness. The results show that both the annual and the biennial deep straw return had a significantly positive influence on the content of soil organic carbon (SOC), humic acid, fulvic acid, and humin in the plough pan (straw-applied horizon), compared to the no-straw return. SOC of the cambic horizon and the C horizon in annual straw return was 28.78%, 47.44% higher than the biennial straw return, but it was 27.58% lower in the plough pan. The SOCD in the plough pan in the biennial straw return was higher than the annual straw return, but their difference in the entire soil profile was not significant. However, the conversion rate of straw carbon to SOC was 18.42% in the annual straw return and 21.05% in the biennial straw return. The straw return amount was not a key factor affecting the SOC sequestration in the cold area; it was restricted by the comprehensive effects of the cold weather, the intensity of soil disturbance, C/V and the initial SOC content. In conclusion, the biennial deep straw return was a better management tool, as it generally had an identical quality and quantity of soil organic carbon and a higher straw conversion rate relative to the annual deep straw return.