Effects of Stone Terracing on Available Phosphorus and Yields on Highly Eroded Slopes in Tigray, Ethiopia

Abstract

ABSTRACT Stone terraces have been widely constructed in the Tigray region of Ethiopia as a response to the severe soil erosion and land degradation of the area. In order to study the effects of stone terracing on plant available phosphorus 42 composite soil samples from 210 test plots were collected and analysed. The results showed increases in plant available P on terrace benches compared to the soil loss zone of terraces and non-terraced land. Mean Olsen-P values were 14.07 mg/kg, 10.35 mg/kg and 10.69 mg/kg from terrace benches, soil loss zone of terraces and non-terraced land, respectively. Calcium phosphate was by far the most dominant P fraction, but it was relatively insoluble in that it did not seem to contribute to plant available P. The iron phosphate fraction was active or labile, however, and seemed to contribute to available P in the soils of the study. The clay and silt textural classes also showed positive correlations with Olsen extract-able P. Grain yield for wheat (Triticum durum) was highest on the terrace benches. It correlated with available P concentrations and silt content only. KEYWORDS: Ethiopiaphosphorussoil conservationstone terracingyields