RUNOFF AND SEDIMENT YIELD CHARACTERISTICS OF SOIL UNDER TOMATO (Lycopersicon esculentum Mill) AND OIL PALM (Elaeis guineensis) CULTIVATION

Abstract

In Nigeria and some sub Saharan African countries, human-induced soil degradation is a common phenomenon. The main problem facing agricultural practices in Nigeria and other developing nations is the rate at which agricultural soil is gradually being lost to erosion. This study was conducted to determine the runoff and sediment yield characteristics of uncultivated bare soil and soils under tomato and oil palm plantation. In addition, impact of rainfall on soil erosion was evaluated. Nine runoff plots were used to examine two land use treatments and uncultivated bare plots in a replicated plot design. Runoff, sediment yield and soil loss were measured on a storm-by-storm basis i.e. for each rainfall event. The soil erosion was estimated for the period of experiment using the Universal Soil Loss Equation (USLE) model. Soil nutrient status and soil physical properties were measured at the end of the experimental season. Uncultivated bare soil plot has the highest mean values of rainfall, runoff and sediment yield (13.85 mm, 5.65 mm and 0.22 ton/ha) respectively, while the least mean values of rainfall (12.56 mm), runoff (4.74 mm) and sediment yield (0.15 ton/ha) were observed in the oil palm cultivation. Cumulative rainfall amounts were 475 mm, 450 mm and 442 mm for bare soil, tomato and oil palm plantation during the study period. A total of 163 mm, 187 mm and 159 mm of runoff volumes were recorded during the study period in tomato cultivation, bare soil plots and oil palm plantation respectively. Land use management significantly (p ≤ 0.001, p ≤ 0.01 and p ≤ 0.05 respectively) affected the nutrients and fertility status of the land use types. The results of the sediment yield analysis have demonstrated that the three different treatments led to different amounts of soil nutrients loss accompanying the sediments. Large loss of soil organic matter (SOM), soil organic carbon (SOC), total nitrogen (TN) and potassium (K) showed the loss of major soil nutrients accompanying sediment loss in the bare plots. The sand, silt and clay fractions were significantly affected by land uses, soil depths and the interaction of land uses (p ≤ 0.001). Soil erodibility index value was highest in uncultivated bare soil (0.097) and lowest in oil palm plantation (0.057). The annual soil loss showed an increasing trend in order: oil palm cultivation (2.53 ton/ha) < tomato cultivation (3.71 ton/ha) < uncultivated bare soil (9.78 ton/ha). Statistical analysis (one-way ANOVA) found a significant (p ≤ 0.05) treatment effect on total soil loss. Post hoc test found that uncultivated bare soil produced a significantly higher soil loss than the other two land use methods. Soil management has a major impact on agricultural productivity and ecosystem sustainability as soils differ in their response to different management. The study emphasizes the management of soil nutrients through effective runoff and sediment yield analysis. It also provides relevant data for effective land use planning and management and serves as a useful guide in the choice of appropriate conservation practice. Improvement in the management of land resource for sustainable agricultural use would be one of the most useful strategies that could help to protect biological diversity for ecosystem sustainability