Abstract

Alternative sources of plant nutrients have now become highly imperative especially for vegetable crop production in Nigeria. Due to the escalating costs, environmental and health problems associated with excessive use of inorganic fertilizers on continuously cropped fields, there is a need for more research on the use of organic manures and residues. A field experiment was conducted in the late growing season from September to December, 2012 in Calabar, a humid forest agroecology in south eastern Nigeria to evaluate the effects of two types of goat manure (GM) application (single and double split doses), five rates of GM (0, 5, 10, 15 and 20 t ha^-1) and 400kg ha^-1 NPK fertilizer (120:60:60 kg ha^-1) rate on soil chemical properties and agronomic performance of sweet maize (Zea mays L. saccharata Strut). Factorial combinations of the treatments were fitted into a randomized complete block design with three replications. The application of GM significantly (P ? 0.05) increased soil pH, organic matter (OM) content, total N, available P, exchangeable K, Ca, Mg and the cation exchange capacity (CEC) status of the soil. Soil exchangeable acidity (EA) was reduced from 1.76 to 0.64 cmol kg^-1 at 20 t ha^-1 GM rate. The 20 t ha^-1 also recorded the highest values for soil pH, OM, P, Ca, Mg and CEC, while the values for residual N and K peaked at the NPK fertilizer treatment. The double split application of GM recorded higher values for growth and yield attributes, and increased soil properties than the single application. Growth and yield parameters such as plant height, number of leaves, leaf area index (LAI), total dry matter (TDM), number and weight of grains/ear and total grain yield were significantly (P < 0.05) increased by GM and NPK fertilizer treatments. The values obtained for all growth and yield parameters except LAI at the 20 t ha^-1 GM rate were not significantly different from those at the NPK fertilizer treatments. The application of 5, 10, 15 and 20 t ha^-1 GM, and NPK fertilizer significantly increased TDM by 11.9, 74.3, 91.9, 106.2 and 104.6%; weight of grains/ear by 16.5, 54.6, 61.4, 100.6 and 94.4% and total grain yield by 46.9, 111.7, 121.0, 127.2 and 140.1% respectively, compared with the control treatment. The interactions between number of applications and rates showed that split applying GM at 20 t ha^-1 maximized TDM, weights of whole and dehusked green ears and total grain yield compared to other GM rates, hence it is recommended.

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