February 2015 Vol. 3 No.2

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Berhe DH
Retta AN

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Review

Soil Improvement by Trees and Crop Production under Tropical Agroforestry Systems: A Review

Daniel Hagos Berhe^* and Abeba Nigussie Retta

Adigrat University, College of Agriculture and Environmental Science, Department of Natural Resources Management, P. O. Box 50, Ethiopia.

*Corresponding Author's Email: danielhgs829@gmail.com

Accepted February 26, 2015

Abstract

The expansion and intensification of the world’s agricultural lands poses the challenge on how to produce enough food without jeopardizing the state of the natural environment. This is especially true in tropical regions, where population growth rates are the highest in the world. At the same time, soils which are less suitable for agricultural production are relatively more abundant and the chemical inputs needed for high productivity are often in scarce supply in remote areas and beyond the economic grasp of smallholder farmers. To address the mentioned problems or challenges different options exists among which agroforestry; agriculture with tree is one. Trees can potentially improve soils through numerous processes including maintenance or increase of SOM, biological N2 fixation, uptake of nutrients from below the reach of crop roots, increased water infiltration and storage, reduced loss of nutrients by erosion and leaching, improved soil physical properties, reduced soil acidity and improved soil biological activity. Thus the purpose of this paper is to discuss on how trees improve the physico-chemical and biological soil conditions and the resulting site amelioration effect on crop productions of the tropics focusing on empirical researches conducted.

Keywords: Agroforestry, Biological N fixation, Fertilizer trees, inorganic fertilizers, Land Equivalent Ratio (LER), Soil Organic Mater, Soil properties