Evaluation of Alley Cropping with Selected Leguminous Multipurpose Tree Species on Maize Production and Soil Fertility at Abaya District, West Guji Zone, Southern Oromia, Ethiopia

Agroforestry as a dynamic ecologically-based natural resources management system that through the integration of trees on farms and in the agricultural landscape diversifies and sustains production for increased socio-economic and environmental benefits. Among those, alley cropping is one of the agroforestry practices which is growing food crops between hedgerows of planted shrubs and trees, preferably leguminous species. A study was conducted to evaluate the contributions of alley cropping for improving maize yield and to evaluate the role of alley cropping for soil fertility improvement in the study area. Susbania sesban and Cajanus cajan trees/shrubs were selected for their potential to improve soil fertility (nitrogen fixing) and have other uses such as fodder. The experiment was designed with four treatments and laid out in randomized complete block design with three replications (block) along the slope gradient. The size of a sampling units (a plot) for each treatment were 20 m x 13 m and the distance between treatments (plots) was 2 m, while; the distance between blocks were 3 m. Alley crop was designed in doubled alley per study plot and the size of an alley crop was 20 m x 5 m. The selected variety of maize (Gibe 2) was sown between alleys of trees/shrubs with recommended spacing of 25 cm and 75 cm between plant and rows of maize respectively. Soil samples were collected and analyzed to evaluate the change made to soil fertility improvement. As a result, a significant difference among arrangements of maize alley cropping in grain yield was observed at (P<0.001). The highest total grain yield was obtained from maize sown with recommended fertilizer (5.16 ton/ha) in 2018 cropping season and maize grown in between alley of Cajanus cajan (4.33 ton/ha) in 2019 cropping season. The soil chemical properties under the alleys plots improved compared to control plots. Positive changes in the soil fertility in terms of soil organic C, total N, soil pH, available K, and exchangeable Ca, Mg and CEC of the top soil layer were detected in alley cropping system. Tree/shrub species of Cajanus cajan seemed to be better than Susbania sesban in improving soil health. Accordingly, it is recommended to grown maize with recommended application of fertilizer and in between alleys of Cajanus cajan tree/shrub species as it has multipurpose importance.