COMPARATIVE EVALUATION OF ORGANIC MANURES, NPK FERTILIZER, AND THEIR INTEGRATION ON MAIZE NITROGEN UPTAKE AND YIELD

Abstract

A field experiment was conducted at the Oyo State College of Agriculture Research Farm, Igbo-Ora, during the 2022–2024 cropping seasons to evaluate the effects of different nitrogen sources on soil nitrogen status, nitrogen uptake, and maize yield. The experiment followed a randomized complete block design with three replications. Treatments included a control, sole applications of compost, poultry manure, pig manure, cow dung (all at 5 t/ha), NPK fertilizer (120 kg/ha), and their integrations (2.5 t/ha organic manure + 60 kg/ha NPK). Data were collected on soil nitrogen, plant N uptake, grain yield, and residual effects. The result revealed that in the first planting season, NPK and its integrations produced the highest grain yield and N uptake. However, residual effects in the second planting season showed superior performance of sole compost (6.0 t/ha), followed by poultry and pig manures, while NPK alone produced lower residual yield (3.6 t/ha). Nitrogen uptake patterns at 4, 8, and 12 weeks after planting reflected similar trends, with compost consistently enhancing soil N levels. The study concludes that while integrated NPK and compost applications improve short-term maize performance, sole compost and other organic manures provide better residual soil fertility and sustainable yield benefits. Application of compost at 5 t/ha, or integration of compost at 2.5 t/ha with 60 kg/ha NPK, is recommended for resource-poor farmers.