RESPONSE OF MAIZE (Zea mays L.) AND SELECTED SOIL PROPERTIES TO INTEGRATED SOIL FERTILITY MANAGEMENT IN ACIDIC SOILS OF ASSOSA, WESTERN ETHIOPIA

Abstract

Soil acidity, which is associated directly with deficiency of nutrients like phosphorus (P); nitrogen (N) and potassium (K) and is accompanied by toxicity of aluminium (Al), iron (Fe) and manganese (Mn) appear to be the major constraint to crop production in western parts of Ethiopia in particular. Therefore, three field experiments were carried out in the acidic soil of Assosa, western Ethiopia, for two years in 2014 and 2015 main growing seasons. Thus, the first experiment was conducted with the objective to assess the effect of integrated application of compost (0, 5 t ha-1), lime (0, 1.5, 3 t ha-1) and P (0, 20, 40 kg P ha-1) on growth, yield components, yield and P use efficiency of maize; and to assess subsequent changes on selected physico-chemical properties of the soil. The second experiment was conducted with the objective to assess the effect of integrated application of compost (0, 5 t ha-1), lime (0, 1.5, 3 t ha-1) and N (0, 69, 138 kg N ha-1) on growth, yield components, yield and agronomic efficiency of maize; and to assess subsequent changes on selected physico-chemical properties of the soil. The third experiment was conducted with the objective to assess the effect of integrated application of inorganic N (0, 69, 138 kg N ha-1), P (0, 20, 40 kg P ha-1) and K (0, 80 kg K ha-1) on growth, yield components, yield, and agronomic efficiency of maize; and to assess subsequent changes on selected physico-chemical properties of the soil. All experiments were laid out in randomized complete block design with three replications. The results of the first experiment showed significant (P<0.05) main effects of year, compost, lime and P on plant height, dry biomass yield, grain yield, agronomic P efficiency and P uptake. There was significant (P<0.05) interaction effects of year with P, compost with P and lime with P on the apparent recovery efficiency of maize. The main effects of lime and compost and interaction effects of lime and year showed significant (P<0.01) effect on the exchangeable Al. The interaction effects of year, lime and P significantly (P<0.01) affected the soil pH, organic carbon (OC), total N and exchangeable acidity of the soil. The interaction effects of year, compost, lime and P significantly (P<0.01) affected the available P of the soil. The results of the second experiment showed significant (P<0.05) interaction effects of year with N on the days to tasseling, LAI, number of ears per plant and grain yield of maize; interaction of year with lime on TKW, grain yield and; while the interaction of compost with lime showed xx significant (P<0.05) effect on plant height and dry biomass yield of maize; interaction of compost and N also showed significant difference on agronomic N efficiency of maize. The interaction effects of year, compost and lime showed significant (P<0.05) effect on the CEC, available P and exchangeable Al. The interactions amongst year, compost, lime and N also showed significant (P<0.05) effect on the soil pH, OC, total N and the exchangeable acidity. In the third experiment the LAI, plant height, ear length, number of kernels per ear, dry biomass yield, grain yield and agronomic P efficiency of maize were significantly (P<0.05) affected by the main effects of N, P and K. The days to tasseling, silking and agronomic N efficiency were significantly affected only by the main effect of K; while the harvest index and agronomic P efficiency were significantly affected by N alone. The main effect of P showed significant (P<0.05) effect on CEC and available P; and the main effect of N showed significant effect on the soil pH and exchangeable acidity. In general, there was a grain yield loss from the first (3.84 t ha-1) to the second (2.84 t ha-1) and to third (2.74 t ha-1) objectives. The soil pH decreased and exchangeable acidity increased due to increasing rate of N in the third experiment, but exchangeable acidity decreased in the first and second experiments due to applied compost and lime even in presence of N, as application of N together with compost and lime have not affected the soil pH and exchangeable acidity. On the other hand, the interaction of compost and lime when applied with P or N highly increased the available P in the first two objectives. Therefore, integrated application of compost (5 t ha-1) and lime (1.5 t ha-1) with P (20 kg P ha-1) or N (69 kg N ha-1) could best be use to improve yield of maize and the soil property.