Intensive agriculture increases soil erosion, runoff, and organic matter decomposition, further resulting in depletion of soil organic carbon (SOC) and total nitrogen (TN). Many agriculture managements have been suggested to improve SOC pools, however, in different researches, the effects of SOC sequestration were contradictory.

Because of the frequent tillage, maize and soybean cultivation has been directly linked to karst land degradation. Therefore, rotation system of maize and soybean has been transformed into conservation agriculture systems (sugarcane, mulberry, and forage grass) in the past 30 years in southwest China. Whether the land use transformation could significantly increase SOC and TN pools remains unknown.

In order to determine whether the SOC and TN pools change following the transformation of maize-soybean fields to the three conservation agriculture systems, researchers from the Institute of Subtropical Agriculture (ISA) of the Chinese Academy of Sciences conducted a regional research in Guangxi Province, southwest China.

They measured microbial biomass C and N (MBC, MBN) and the content of SOC and TN, and further estimated SOC and TN pools in three soil horizons (0-10cm, 10-20cm, and 20-30cm) in maize-soybean rotation, sugarcane, mulberry, forage grass, and forest.

The researchers found that the SOC and TN pools were not significantly higher in sugarcane and mulberry fields than in maize-soybean rotation fields, while SOC and TN pools in forage grass fields were higher by 56.3 and 29.4% relative to the maize-soybean fields, but were lower by 38.3% and 21.8% compared to the forests, respectively.

"The concentrations of MBC and MBN varied in similar patterns as SOC and TN pools, and the MBC:SOC and MBN:TN ratios were higher in the forage grass fields, suggesting forage grass cultivation increased soil organic matter quality compared to other types of agriculture fields,” said Prof. LI Dejun.

The work was found by the National Key Research and Development Program of China, the National Key Basic Research Program of China, the Strategic Priority Research Program of Chinese Academy of Sciences, and the National Natural Science Foundation of China.

The study suggested that forage grass cultivation was identified as an efficient solution to promote SOC and TN pools, and has been published in the journal of Land Degradation and Development with the title of “Forage grass cultivation increases soil organic carbon and nitrogen pools in a karst region, southwest China”, (29) 12 October 2018, pages 4397- 4404. The details could be found at https://onlinelibrary.wiley.com/doi/pdf/10.1002/ldr.3200

Contact: LI Dejun

E-mail: dejunli@isa.ac.cn

Institute of Subtropical Agriculture, Chinese Academy of Sciences