Influence of Agricultural Land Use Change on the Selected Physico-Chemical Soil Properties in Kilombero Valley Floodplain, Southeastern Tanzania

Abstract

Land use change attributed to increased population pressure, government policies, economic development, and biophysical factors has affected the soil properties, which plays an important role in agricultural productivity. Thus, this study investigated the effects of changes in land use on some selected soil physicochemical properties in the Kilombero valley floodplain, Tanzania. Soils were collected from the pristine wetland, forest, upland cultivation, and rice farm. The agricultural land considered for this study has been converted from forest and wetland, and under cultivation for over 10 years. The total of 48 soil samples were collected from depth of 0-20cm and 20-40cm to investigate the variance of cation exchange capacity (CEC), total organic matter (TOM), total nitrogen (TN), soil pH, bulk density (BD), total phosphorus (TP), soil moisture content (SMW) and water stable aggregates (WSA) in the four selected land use types. The two-way analysis of variance (ANOVA) was employed. The results showed that TOM, TN, CEC, SMC, and WSA have significantly decreased (p-value, <0.05) while BD, soil pH and TP have significantly increased (p-value, <0.05) as the forest and wetland converted to upland cultivation and rice farm, respectively. Moreover, Post Hoc Test of LSD revealed that there is a significant difference at P<0.05 for all the selected soil physicochemical properties between wetland and rice farm, showing that the wetland is highly sensitive to declining soil fertility, particularly organic matter. Therefore, this study recommends the imposition of agricultural practices such as agro forestry, incorporation of crop residues, the use of organic manures, minimum tillage, and crop rotation to facilitate soil organic matter building up. Moreover, to reduce the encroachment of farmers into wetland and forest area serious attention should be given to the development of sustainable land use planning and management in the Kilombero valley floodplain.