Effective Practices in Mitigating Soil Erosion from Fields
This is an advance summary of a forthcoming article in the Oxford Research Encyclopedia of Environmental Science. Please check back later for the full article.
Soil erosion by water is a natural process that cannot be prevented. Soil erosion depends on many factors, and a distinction has to be made between humanly unchangeable (e.g., rainfall) and modifiable (e.g., length of the field) soil erosion factors. Soil erosion has both on-site and off-site effects. Soil conservation tries to combine modifiable factors so as to maintain erosion in an area of interest to an acceptable level. Strategies to control soil erosion have to be adapted to the desired land use. Knowledge of soil loss tolerance, T (i.e. the maximum admissible erosion from a given field), allows the technician or the farmer to establish whether soil conservation practices need to be applied in the area or not. Accurately determining the tolerable soil erosion level for an area of interest is crucial for choosing effective practices to mitigate this phenomenon. Excessively strict standards for T would imply over-expenditure of natural, financial, and labor resources. Excessively low T values may lead to excessive soil erosion and hence to decline of soil fertility and productivity and to soil degradation. In this last case, less money is probably spent for soil conservation, but ineffectively. Basic principles to control erosion for different land uses include maintaining vegetative and ground cover, incorporating biomass into the soil, minimizing soil disturbance, increasing infiltration, and avoiding long field lengths. Preference is generally given to agronomic measures over mechanical measures since the agronomic measures reduce raindrop impact, increase infiltration, and reduce runoff volumes and water velocities. Agronomic measures for soil erosion control include choice of the crops and crop rotation, applied tillage practices, use of fertilizers and amendments, and installation of vegetative barriers at the downslope end of the field. Mechanical measures include contour, ridging, and terracing. These measures cannot prevent detachment of soil particles, but they oppose to the sediment transport downhill and can be unavoidable in certain circumstances, at least to supplement agronomic measures. Simple methods can be applied to approximately predict the effect of a given soil conservation measure on soil loss of an area of interest. In particular, the simplest way to quantitatively predict mitigation of soil erosion due to a particular conservation method is the Universal Soil Loss Equation. Despite its empirical nature, this model still represents the best compromise between reliability of the predictions and simplicity in terms of input data, which are generally very difficult to obtain for other soil erosion prediction models. Soil erosion has to be controlled soon after burning.