Source: Alegre, J.C., and D.K. Cassel. 1996. Dynamics of soil physical properties under alternative systems to slash-and-burn. Agric. Ecosys. Environ. 58:39-48.

The traditional slash-and-burn cropping system of the humid tropics is being replaced by continuous cropping systems as demand for land increases with the rapidly growing population. Methods of clearing the land and subsequent agricultural management systems impact the physical structure of the soil. Soil structure is important to long term productivity and sustainability of the agricultural system. This paper examines the impact of slash-and-burn and some alternative cropping systems on the physical properties of the soil. Long term experiments were conducted using three methods of clearing the land: slash-and-burn, bulldozing with a straight blade, and bulldozing with a shear blade. After clearing, different systems of tillage and cropping were examined including planting in raised beds and four agroforestry systems: multistrata alley cropping, peach palm production, low input shifting agriculture, and high input continuous cropping. The soil physical properties that were measured were bulk density, the soil water characteristic, infiltration rate, aggregate stability, and penetrometer cone resistance. Bulk density of the top layer of soil was 1.46 Mg/m3 on land cleared by slash-and-burn, compared with 1.63 Mg/m3 for land cleared by bulldozer. Mechanical clearing with a straight blade reduced the infiltration rate from 420 mm/hour before clearing to 35 mm/hour after clearing. Bulk density of the top layer of soil continued to increase for mechanized, high input systems while bulk density eventually decreased for agroforestry systems. The authors conclude that mechanical land clearing changes the soil physical properties the most (more than slash and burn), but agroforestry systems using cover crops and trees actually improve the soil physical properties.

Abstract author: Erin C. Cudney, 26 October 1999.

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