Land Use Changes Affecting Soil Organic Matter Accumulation in Topsoil and Subsoil in Northeast Thailand

Benjapon Kunlanit,Laksanara Khwanchum,Patma Vityakon

doi:10.1155/2020/8241739

Abstract

The objectives of this study were to investigate effects of land use on accumulation of soil organic matter (SOM) in the soil profile (0–100 cm) and to determine pattern of SOM stock distribution in soil profiles. Soil samples were collected from five soil depths at 20 cm intervals from 0 to 100 cm under four adjacent land uses including forest, cassava, sugarcane, and paddy lands located in six districts of Maha Sarakham province in the Northeast of Thailand. When considering SOM stock among different land uses in all locations, forest soils had significantly higher total SOM stocks in 0–100 cm (193 Mg·C·ha−1) than those in cassava, sugarcane, and paddy soils in all locations. Leaf litter and remaining rice stover on soil surfaces resulted in a higher amount of SOM stocks in topsoil (0–20 cm) than subsoil (20–100 cm) in some forest and paddy land uses. General pattern of SOM stock distribution in soil profiles was such that the SOM stock declined with soil depth. Although SOM stocks decreased with depth, the subsoil stock contributes to longer term storage of C than topsoils as they are more stabilized through adsorption onto clay fraction in finer textured subsoil than those of the topsoils. Agricultural practices, notably applications of organic materials, such as cattle manure, could increase subsoil SOM stock as found in some agricultural land uses (cassava and sugarcane) in some location in our study. Upland agricultural land uses, notably cassava, caused high rate of soil degradation. To restore soil fertility of these agricultural lands, appropriate agronomic practices including application of organic soil amendments, return of crop residues, and reduction of soil disturbance to increase and maintain SOM stock, should be practiced.

Highlights

Soil organic matter (SOM) is a key integral indicator of soil quality [1, 2]
Soil depth is an important factor influencing the variation in SOM [49], and lower soil layers have been found to contribute to longer term storage of C than topsoils as the loss of soil C in lower soil layers is less than their upper layer counterpart [65, 66]
Our results have shown conclusively that land use exerted significant influence on SOM stocks in soil profiles

Summary

Introduction

Soil organic matter (SOM) is a key integral indicator of soil quality [1, 2]. Both soil organic carbon (SOC) and soil organic nitrogen (SON) are attributes of SOM used to describe SOM various functions [1]. e SOM dynamics are dependent on native vegetation, climatic conditions, soil types, management practices, land use history, and time of land conversion [3, 4]. Numerous studies around the world have shown that land use change encompassing changes in vegetation cover, crop type, and agricultural practices has bearings on SOM accumulation. In Ethiopia, SOM stock in forest soil at 0–20 cm depth was higher than in agricultural land (i.e., eucalyptus plantation, grazing land, and cropland) [3, 7, 8]. Another study in Brazil on land use affecting SOM was that of coconut orchard treated with chemical-organic fertilizer application, leguminous cover crops, and mulching compared with forest soil. Conversion from forest (close nutrient cycling system) to various crop cultivations (open system) with different agricultural practices alter soil processes involved in SOM formation and accumulation in topsoil and subsoil layers (>20–100 cm soil depth) of sandy soils. We hypothesized that land use change from forest to cropland reduces SOM stock in soil profile. In order to test this hypothesis, we examined stocks of SOM in the soil profile (0–100 cm) as influenced by land use changes in the selected locations

Materials and Methods

Results and Discussion

Conclusions