Effect of Urea and Compost Amendments on Soil Microbial Activities and Chemical Properties

A pot experiment was conducted in the screenhouse of the College of Plant Science and Crop Production, University of Agriculture, Abeokuta, Nigeria to investigate the effect of urea and compost on maize (Zea mays L.), soil microbial activities and chemical properties. The experiment consisted of two rates of urea (0, 0.25 t/ha), and three rates of compost (0, 10 and 20 tonnes per hectares). Data were collected on the following parameters: Microbial N, Microbial biomass C, Microbial biomass P, Percentage nitrogen, Microbial respiration, C/N ratio, protease, urease, cellulase, plant height, stem girth and number of leaves. The data collected were subjected to analysis of variance. The plants in pots amended with urea had significantly higher (p ≤ 0.05) plant height, leaf area stem girth, fresh and dry root weight, fresh and dry shoot weight and soils amended with urea had significantly higher (p ≤ 0.05) microbial biomass (P), microbial respiration, phosphorus, organic carbon, protease, urease and cellulase. Plants amended with compost had significantly higher (p ≤ 0.05) plant height, leaf area number of leaves, fresh and dry root weight, fresh and dry shoot weight, urease, and cellulose. Compost did not have significant effect on stem girth. Similarly, soils amended with compost had significantly higher microbial biomass (N, P, and C), microbial respiration, phosphorus and organic carbon. Interaction of compost control (0 t/h) and urea was significantly lower that urea + 10 t/h compost and urea + 20 t/h for urease, protease, cellulose, phosphorous and organic carbon. It was however insignificant in the other treatments. Similarly, absolute control was significantly less than non urea + 10 t/h and non-urea + 20 t/h in plant height, stem girth, number of leaves, microbial respiration, urease, cellulose, phosphorus and organic carbon while the others were insignificant. Conclusively, integration of urea fertilizers with organic manures can be used with optimum rates to improve crop productivity on sustainable basis. However, this study will be useful in maintaining sustainable nutrient management programs in future to improve crop productivity with high efficiency and minimum nutrient loss.