SOIL CHARACTERIZATION, LAND USE TYPES AND EFFECTS OF LIMING AND PHOSPHORUS ON SELECTED SOIL PROPERTIES AND MAIZE (Zea mays L.) YIELD IN TIRO AFETA DISTRICT OF JIMMA ZONE, SOUTH-WEST ETHIOPIA

Abstract

Sustainable agricultural production to meet the increasing demands forfood, fiber and fuel requires understanding of soil characteristics, distribution over an area and effects of land use types and management on soil properties for efficient utilization of limited land resources. A field study was conducted in Tiro Afeta District of Jimma Zone, Southwest Ethiopia, to characterize and classify soils along a toposequence; assess the effects of land use types on selected soil properties; and investigate the effects of liming and phosphorus fertilizer application on soil properties and performance of maize. Five representative pedons were opened for the first objective; soil samples were collected from the 0-20 cm depth of five adjacent land use types (forest, grazing, cultivated, degraded and coffee lands) for the second objective; and five levels of lime (0, 0.5, 1.0, 1.5 and 2 tones h-1 ) and P fertilizer (0, 46, 92, 138 and 184 kg P2O5 ha-1 ) were used for achieving the third objective. Soils of the study area showed spatial variability in their properties within and across pedons. The soils have a clay texture, with bulk density values ranged from 1.11 to 1.33 g cm-3 . The pH-H2O values varied from 5.6-5.8 at the surface layers and 5.74 to 6.30 in sub-surface layers. The soils had 0.50-1.50% organic carbon, 10.50-13.95 mg kg-1 available P, and 20.05-26.40 cmolc kg-1 soil cation exchange capacity. The Reference Soil Groups identified are Haplic Nitisols (Orthodystric), Gleyic Vertisols (Mesotrophic), Stagnic Vertisols (Eutric), Haplic Nitisols (Orthoeutric) and Vermic Phaeozems (Chromic). The results of study on effects of land use types on soil properties revealed the negative impact of cultivation on most of the soil parameters as compared to the forestland. The field experiment results indicated that phosphorus fertilization did not significantly increase maize production as compared to the control treatments due probably to the rates were not high enough to bring about statistically significant changes. However, there were improvements of different levels in the measured plant parameters as compared to the control treatment. The results further demonstrated that soil properties, such as pH, available P, exchangeable Ca2+ , cation exchange capacity, and percent base saturation were increased with combined application of lime and P fertilizer at optimum rates. From the results obtained, it can be concluded that, as a result of differences in soil properties along the toposequence, different soil types were developed with different potentials and constraints and application of lime and P fertilizer could improve productivity of maize in the study area.