Soil Erosion Risks and Farmers’ Adaptation Strategies in Anambra State, Nigeria

Abstract

Soil erosion is a major land degradation problem in Anambra State, Nigeria. Research attention has focused mainly on gully erosion to the neglect of interrill erosion. Farmers’ response to manage erosion menace is also scarcely studied. The study investigated soil erosion risks and farmers’ adaptation strategies. The study objectives comprised the following: 1. Assessed the variability in rainfall in Anambra State, 2. Assessed soil characteristics and determined the in-situ soil loss, 3. Modelled soil erosion using the RUSLE model and 4. Appraised the farmers’ adaptation strategies in Anambra State. The variations in rainfall were assessed using trend analysis, extraction of climate change indices following the ETCCDI, and the climatic water balance. Regression and correlation were used to determine the relationship between rainfall, and soil moisture with soil loss. The in-situ assessment was done during the 2022 rainy season at Isu-Aniocha, Aguleri, and Oko using runoff plots. The RUSLE model was used to determine the mean annual soil erosion rate in Anambra State. Then, the farmers were purposively surveyed using questionnaire to elicit information on their perception of soil erosion risks and their adaptation strategies. The results show that there was an increasing trend in the monthly, annual, and seasonal rainfall except for the MAM season. A significant positive correlation exists between soil loss and soil moisture. However, at Aguleri, it is not significant. High permeability of the soil suppressed the impact of soil moisture. Soil loss from the bare fallow was 6 to 11 times higher than that from the vegetated plot depending on the plot size. The mean annual soil loss in the field was 27.76 t ha-1yr-1 and that from the model was 25.25 t ha-1yr-1. The models' performance had a mean bias error (MBE) of -3.00 t ha-1 yr-1, MAE of 9.34 t ha-1 yr-1, and correlation coefficient of 0.88 indicating an underestimation of the soil erosion but with a good performance. This showed that the RUSLE model is good for erosion modelling and soil conservation planning in the State. Soil erosion increased from 2017 to 2022 (21.32 to 25.25 t ha-1 yr-1) and to 31.22 and 31.79 t ha-1 yr-1 in 2060 under the SSP245 and SSP585 scenarios. The results showed that interannual changes in soil loss were highly influenced by the C-factor more than the erosivity. This does not necessarily imply that erosivity is unimportant but rather that its role in interannual variation was outweighed by the dynamics of the C-factor. The farmers perceive soil erosion as an environmental problem. However, their adaptation strategies were low. Thus, due to the rising soil erosion and poor adaptation by farmers in the State, the authority should embark on mass awareness creation by engaging the farmers on the need for the implementation of soil conservation measures.