Effects of land management practices on soil physicochemical properties of selected sites in the Migina catchment, Kansi sector, Gisagara District, southern province of Rwanda

Abstract

Land use changes from natural ecosystems into managed ecosystems may have impacts on soil structure and quality. Land management practices contribute to the change of soil properties and agriculture production. Rwanda's livelihood and social economy is strongly dependent on agriculture. Moreover, the exponential Rwandan population growth is making a severe pressure on natural resources including forests. In order to contribute to sustainable and environmentally friendly agriculture, the present research focused on the impact of land management on soil quality. Many scholars have proved that even the downhill surface water quality is mainly affected by unsustainable land management practices. This research was carried out to determine the impact of land management on soil quality in order to contribute to its protection and a sustainable agricultural production for food security, soil and water conservation. This study was conducted at Akaboti cell, Kansi Sector, Gisagara District of the Rwandan Southern Province, exactly in the Migina catchment watershed with different agricultural activities for comparison. The following physicochemical characteristics were evaluated: soil reaction (pH), organic carbon, Nitrogen, Phosphorus, Exchangeable basis (Calcium, Sodium, Magnesium, Potassium), exchangeable acidity, soil texture, moisture content, bulk density, and electrical conductivity. The laboratory results showed that soils across the different land management practices were dominated by the soil texture classified as sandy loam textural class. The soil bulk density varied between 0.96 and 1.44 g /cm-3, the soil porosity was 50.2 to 52.08 % in terraced land; 47.2 to 58.16 % in trenches; 53.8 to 63.87 % in agroforestry and 53.08 to 53.8 % in forested land. In general values for this parameter ranged from 56.39 to 58.9 % in managed lands and 45.9 to 51.84% in non-managed land (the control). The soil pH ranged from 4.73 to 5.14 for the radical terraced land, 5.79 to 5.29 for trenches, 6.29 to 5.79 for agroforestry land, 4.49 to 4.93 for forested land, 5.11 to 6.34 for amended soil and 4.69 to 5.27 for the control. The electrical conductivity was low in all treatments ranging from 0.076 to 0.39. The values of mineral nitrogen measured in managed lands were higher compared to those measured in the control. Ammonium values ranged from 2.55 to 7.24 mg kg-1 while those of nitrate ranged from 4.36 to 28 mg kg-1. Available P values were higher in the managed land than in the control. The values of available P ranged from 8.55 to 17.10 mg kg-1. The values of exchangeable bases were slightly higher in managed land than in control; however, those values were generally low. Generally, the agroforestry land showed high nutrients values compared to the control and other treatments. From the results of this study, it is clear that the land management practices have generally a positive impact on soil properties. Farmers are therefore advised to adopt those practices, especially agroforestry.