Relationship between Rainfall, Surface Runoff and Soil Loss on an Experimental Farm in the Middle Belt of Nigeria

Abstract

Rainfall induced depletion of soil nutrients resulting from runoff and soil erosion are a main threat for agricultural lands, tending to reducing soil fertility, soil productivity and eventually leading to the un-sustainability of agricultural production systems. It is based on the problems associated with soil loss that the required mulch type, mulch cover and slope of the farming field need to be properly investigated and determined. This research therefore analyzed surface runoff and soil loss under different mulch treatment at a farm site in Benue State, in the middle-belt region of Nigeria. The main aim is to analyze the effect of varied mulching will have on runoff and soil loss volumes resulting from rainfall and examine the implication of the results on soil management practice in the region. Experimental plots of 20m long by 3m wide were carved out with an outlet down slope of 1.5m² (20m×3m+1.5m² = 61.5m² ) were bordered with corrugated iron sheets and inserted with runoff and soil loss receptors. The experimental plots were treated with weighted organic materials (mulching, in tons) and planted with maize with plots of zero (0) tons as control (T1). The maize planted was spaced 25cm on row and 75cm on columns. The experimental plots were replicated and symbolized as (T1) = bare surface (0 tons A, B and C), (T2) = surface mulch +maize (4 tons A, B and C) and (T3)= surface mulch + maize (8 tons A, B and C). Rainfall data was collected over ten (10) rain events and runoff and soil loss measurements was analyzed with using correlation statistics, variability and regression. The results show that 96.14% runoff occurs on T1, 3.22% and 0.63% runs off on the T2 and T3 respectively with corresponding 193.7kg, 3.1kg and 0.5kg soil loss. The study finds out that mulching reduces simultaneously both runoff and soil loss in the region. The amount rainfall only has no significant effect on amount of runoff and volume of soil loss. The study revealed that, surface cover combined with simple cropping controls runoff and soil loss by 67% and 61% respectively. This will be useful to farmers in addition to the fact that mulching also has a collateral benefit of stimulating microbial activities and regulating soil moisture and temperature.