Dynamic Changes of Soil Surface Organic Carbon under Different Mulching Practices in Citrus Orchards on Sloping Land.

Chiming Gu,Runhua Zhang,Margot Brooks,Xiao Wang,Yi Liu,Fang Chen,Ibrahim Mohamed,Zhiguo Li,Min Jiang,Xinxin Nie,Dafeng Hui

doi:10.1371/journal.pone.0168384

Abstract

Mulching management has been used in many places all over the world to improve agricultural sustainability. However, the cycling of carbon in the soil under applications of mulch on sloping arable land is not yet fully understood. A four-year field experiment was carried out in Xiaofuling watershed of Danjiangkou reservoir in China. The object was to evaluate the effects of the application of straw mulch (ST) and grass mulch (GT) on dynamic changes in soil organic carbon and its fractions. Results showed that mulch applied on the soil surface increased the contents of SOC and its active fractions in the soil. Compared to the control without cover (CK), ST and GT treatments increased the contents of SOC, LOC, DOC, POC and EOC by 14.73%, 16.5%, 22.5%, 41.5% and 21%, respectively, in the 0–40 cm soil layer, and by 17%, 14%, 19%, and 30%, respectively, in the 0–100 cm soil layer. The contents of organic carbon and its active fractions decreased with increasing soil depth in all of the treatments. SOC was accumulated in the period of December to the following March. The contents of soil DOC and LOC were high in January to March, while the contents of soil POC and EOC were high in June to September. The relative contents of soil organic carbon fractions were POC > EOC > LOC > DOC over the four years. Straw mulching had no significant effect on the changes in soil organic carbon active fractions during the different periods. Based on this long-term field experiment in Danjiangkou reservoir, we found that straw mulching had a significant effect on soil, increasing SOC content and stock in slopping arable land, and that live grass mulching was more effective than rice straw mulching. We discuss possible optimal periods for the implementation of mulching practices on sloping land.

Highlights

Soil erosion in hill and mountain regions is a major issue, especially when combined with climate change
This uncertainty may be related to the complex processes of soil C sequestration [14], especially unclear for the dynamics of soil labile C fractions such as light organic carbon (LOC), dissolved organic carbon (DOC), particulate organic carbon (POC) and oxidizable organic carbon (EOC)
A four-year field experiment demonstrated that the adoption of grass clover mulching treatment (GT) and straw mulch (ST) could significantly increase the contents of total Soil organic carbon (SOC) and SOC fractions in sloping arable land

Summary

Introduction

Soil erosion in hill and mountain regions is a major issue, especially when combined with climate change. Previous studies indicated that these labile C fractions accounted for a small part of soil total organic carbon They had high turnover rates and fast mobility, and were altered according to local climate, soil texture and soil management, especially in disturbed agricultural systems, including arable lands [15]. They have a large effect on soil biochemical processes, nutrient and carbon cycling [16]. Understanding the character of SOC and labile C fractions, and their relationships with soil properties, is vital for a better assessment of the effects of management on soil properties, nutrient cycles, soil erosion, and C sequestration of sloping arable land

Objectives

Methods

Conclusion