Soil Organic Carbon and Nitrogen Stocks Following Land Use Changes in a Sub-Humid Climate

Abstract

There has been an incessant conversion of natural forests to agricultural land uses such as farmlands, grasslands and parkland agro-forestry in Africa during the last century. This study investigated changes in soil organic carbon (SOC) and total nitrogen (TN) stocks following the conversion of a natural forest to coffee-based agro-forestry, grazing grassland and well-managed maize farm in a sub-humid tropical climate of Ethiopia. Soil samples (up to 1m depth) were taken from each of these four land use types. Taking the natural forest as a baseline and with duration of 35 years since land use conversion, the total SOC and TN stocks were not significantly different (P > 0.05) among the different land use types when the entire 1m soil depth was considered. However, in the upper 0-10cm soil depth, the SOC and TN stocks were significantly higher (P < 0.05) in the natural forest than the agricultural land use types. There were different patterns of SOC and TN distributions along the soil depths for the different land use types. The SOC stocks decreased with depth in natural forest, but did not show any increasing or decreasing trends in maize farm, grazing grassland, and coffee-based agroforestry. The results of this study revealed that the negative effects of converting natural forests to agricultural land use types on SOC and TN can be prevented through appropriate land management practices in cultivated and grazing lands and use of proper agroforestry practices in a sub-humid tropical climate.

Effects of Land-Use Dynamics on Soil Organic Carbon and Total Nitrogen Stock, Western Ethiopia

“…Tis was attributed to an increase in the mineralization rate and a decrease in the soil accumulation of soil organic carbon and total nitrogen stock; even though the results of a one-way ANOVA revealed an insignifcant diference in the carbon-to-nitrogen ratio, it was estimated to decline by 3.32% with natural forestland use types. Te higher correlation between soil organic carbon and total nitrogen stock showed that the main source of total nitrogen is the decomposition of organic matter [55,63]. In general, the soil C : N ratio is an essential indicator of the soil nutrient storage and recycling capacity, carbon storage, greenhouse gas emissions, and the microorganism community structure that changes the soil quality of ecosystems.…”