COMPARATIVE EFFECTS OF LIME, POULTRY MANURE AND NPK COMPOUND FERTILIZER ON SOIL PHYSICOCHEMICAL PROPERTIES AND YIELD OF MAIZE IN AN ULTISOL OF SOUTHEASTERN NIGERIA.
Field and greenhouse experiments were conducted at the University of Nigeria, Nsukka, in 2011, to examine the effects of lime, poultry manure and NPK 15-15-15 on the soil nutrient content and yield of maize. The experiment was first carried out in the greenhouse and later evaluated in the field. The experimental designs used were 6 x 4 factorial in completely randomized design (CRD) and randomized complete block design (RCBD) for the greenhouse and field experiments respectively. Two factors were considered in the experiments. Factor A: different fertilizer rates and their combinations viz: T1 (200 kgha- NPK + 6 tha-1 PM), T2 (300 kgha-1NPK + 4 tha-1 PM), T3 (400 kgha-1NPK + 2 tha-1 PM), T4 (400 kgha-1NPK only), T5 (8 tha-1 PM only), T6 (Control; no fertilizer application). Factor B: liming levels: pH 6.0, pH 6.5, pH 7.0 and pH 5.5 (control). Maize plant was used as a test crop. In the greenhouse trial, among the six treatments applied, T5 (8 tha-1 PM only) had significant (P < 0.05) effect on soil available P, soil pH, cation exchange capacity and exchangeable magnesium but not on other parameters measured. For the field evaluation, treatment T1 had significant (P < 0.05) effect only on soil aggregate stability but not on mean weight diameter (MWD), aggregate stability (AS), bulk density, total porosity and hydraulic conductivity. Also this treatment had significant (P < 0.05) effect on the soil nutrient contents than other treatments applied. This was similar to that obtained from the greenhouse trial. Soil limed to pH 7.0 significantly (P < 0.05) decreased the soil acidity and increased the exchangeable calcium. A combination of NPK and poultry manure at various rates had better effects than either sole application of NPK or poultry manure on maize parameters measured namely: plant height, leaf number, leaf area index, tasselling number, cob weight, chaff weight, and dry matter. Similarly, liming the soil to different pH levels had significant (P < 0.05) effect on maize plant performance. The highest plant physiological parameters were obtained from the soil limed to pH 7.0 while soil limed to pH 6.0 gave the least plant parameters. The order of performance was as follows: soil limed to pH 7.0 > pH 5.5 (control) > pH 6.5 > pH6.0 in plant parameters namely plant height, cob weight, tasselling number, and seed weight. From the study, soil of pH 5.5 with the application of 200 kgha-1 NPK + 6 tha-1 or 8 tha-1 PM only is recommended for maize production.