Agroforestry for Soil Conservation

Abstract

Soil conservation refers to the maintenance of soil fertility and erosion control. Soil fertility maintenance in agroforestry systems is achieved through the addition of organic matter, typically through litterfall and mulching, while erosion control is achieved through the mitigation of soil losses. Agroforestry systems have been proven to be efficient in soil erosion control. In semiarid Kenya, Senna siamea mulch cover reduced soil losses to only 13 % of the standard average loss and barrier hedgerows reduced the loss to 2 %. Leucaenea leucocephala-maize plots in a subhumid climate in Malawi reduced soil loss on a steep (44 % gradient) to 2 tons ha⁻¹ year⁻¹, compared with a loss of 80 tons ha^-1 year^-1 in maize plots without agroforestry on a similar slope. On a less steep slope (4 %) in the Himalayan valley of India, runoff was reduced by 27 %, and soil loss by 45 % using a contour cultivation of maize. Contour tree rows or Leucaena hedges reduced runoff and soil loss by 40 % and 48 %, respectively, compared to the maize plot. Soil loss was reduced to about 12.5 Mg (or tons) ha⁻¹ year⁻¹, a significant improvement over fallow plots, which lost about 39 tons ha⁻¹ year⁻¹. Agroforestry practices that are widely used in the tropics for erosion control include crop combinations, multi-storey tree gardens, alley cropping, and windbreaks or shelterbelts. Effective windbreaks provide semi-permeable barriers to wind over their full size, from the base of the windbreak up to the top of the tallest trees.