EVALUATION OF SOIL ACIDITY AND EFFECTS OF AMENDMENTS ON SELECTED SOIL PROPERTIES AND YIELD OF MAIZE (Zea mays L.) IN EBANTU DISTRICT, WESTERN HIGHLANDS OF ETHIOPIA

Abstract

In highly weathered and leached soils, acid soil infertility is a major limitation to crop production. Three major experiments were conducted under laboratory, greenhouse, and field conditions to assess soil acidity status of surface soils under three land use types (forest, cultivated, and grazing lands), evaluate the effects of lime, vermicompost (VC), and chemical phosphorus (P) fertilizer on selected soil properties, and investigate the effects of the three amendments on selected post-harvest soil properties and yield of maize, respectively. For the incubation experiment, three lime rates (2, 4, and 6 tons CaCO3 ha-1), three VC rates (2.5, 5, and 7.5 tons ha-1), and three chemical P fertilizer rates (20, 40, and 60 kg P ha-1) were used. For the field experiment, two lime rates (0 and 4 t CaCO3 ha-1), three VC rates (0, 2.5, and 5 t VC ha-1), and three chemical P fertilizer rates (0, 20, and 40 kg P ha-1) were used. The results indicate that the pH (H2O) of the surface soils ranged from 4.85 (very strongly acidic) in cultivated lands to 5.33 (strongly acidic) in the forest land, indicating that soil acidity is a serious problem in the study area. The exchangeable acidity varied from 0.73 cmolc kg-1 in the forest land to 2.44 cmolc kg-1in the cultivated land while the exchangeable Al ranged from 0.15 cmolckg-1 in the forest land to 2.01 cmolc kg-1in the cultivated land. The percentage acid saturation ranged from 3% in soils under forest land to 13% in soils of the cultivated land. The highest increment of pH from 4.83 to 6.05 and decrement of exchangeable Al from 1.70 to 0.09 cmolc kg-1 were obtained with combined use of lime at 4 tons CaCO3 ha-1 and 7.5 tons ha-1 VC. A 93% reduction in exchangeable acidity was recorded from the use of 6 tons CaCO3 ha-1 alone, while combined application of 4 tons CaCO3 ha-1 with 7.5 tons ha-1 VC reduced soil acidity by 81%. Various combinations of the treatments also improved soil OM, TN, available P and exchangeable bases significantly as compared to soils that did not receive any of the treatments. The results of twoyears field experiments revealed that significantly higher early tasseling days (102), silking days (109), leaf area index (5.91), plant height (3.48 m), cob length (47.8 cm), number of grain per cob (644), and above ground dry biomass yield (22 t ha-1) were recorded in treatments that received 5 t ha-1 VC and chemical P fertilizer at the rate of 40 kg ha-1 combined with 4 tha-1 lime. The highest 1000-seed weight (508 g), grain yield (4.87 t ha-1), and harvest index (24%) were obtained from combined application of 2.5 t ha-1 VC and 40 kg P ha-1 with lime (4 t CaCO3 ha-1). The integrated application of 5 t VC ha-1with lime increased pH, available P, exchangeable bases, cation exchange capacity, and decreased exchangeable acidity and Al. Organic matter and total N also increased by the application of VC and lime. Understanding the current status of surface soil acidity and application of VC alone or integrated application of VC and chemical xix P fertilizer with lime to strongly acidic soils can be recommended for ameliorating acidity of the soils and optimum production of maize.