ABSTRACT
Maize productivity is low in Nigeria due to declining soil fertility among other factors. This can be improved through balanced soil fertilization with the adoption of improved variety and optimum stand density. Trials were conducted in 2021 and 2022 on NPK, agrolyser and plant population for maize grain production at the Experimental Farm of the Faculty of Agriculture, University of Benin, Benin City, Nigeria. This study involved three experiments: (I) Evaluation of NPK fertilizer types and rates on growth and yield of two maize varieties. It involved two NPK fertilizer types (NPK 20:10:10 and NPK Mg 12:12:17: 2), two maize varieties (SUWAN-1-SR and Oba Super 13) and four NPK fertilizer rates (0, 400,600 and 800 kg ha-1 ) laid out in 2 x 2 x 4 factorial fitted into a randomized complete block design (RCBD) in three replicates (II) Influence of NPK fertilizer supplemented with agrolyser on the growth and yield of two maize varieties. This involved two maize varieties (SUWAN-1-SR and Oba Super 13), three NPK 15:15:15 rates (0, 400, and 600 kg ha-1 ), and four agrolyser rates (0, 0.8, 1.6, and 2.4 kg ha1 ) were laid out in 2 x 3 x 4 factorial arrangements fitted into a RCBD with three replicates. Experiment I and II were conducted in 2021. (III) Evaluation of number of plants per stand, NPK fertilizer and agrolyser rates for maize grain production. Three NPK 20:10:10 rates (0, 600, and 800 kg ha-1 ), three agrolyser rates (0, 1.6 and 2.4 kg ha-1 ) and number of plants per stand (1, 2, and 3 plants) were laid out in 3 x 3 x 3 factorial arrangement fitted into a RCBD and replicated three times. This trial was conducted twice (early and late cropping seasons) in 2022. Data were collected on vegetative characters, days to flowering, yield and yield components, nitrogen use efficiency (NUE), post-harvest soil chemical properties, nutrient content and uptake of maize grain. Results from experiment I showed that plants derived from Oba Super 13 variety were taller with larger leaf area index (LAI) than SUWAN-1-SR plants. Plants fertilized with NPK 20:10:10 produced larger LAI than those treated with NPK Mg 12:12:17: 2. Increased fertilizer application rates increased vegetative characters of maize. Grain yield was higher in Oba Super 13 than in SUWAN-1-SR variety. NPK 20:10:10 treated plants had higher grain yield and NUE than those that received NPK Mg 12:12:17: 2. The highest NUE was observed on plants fertilized with 600 and 800 kg ha-1 NPK. Grain produced from Oba xviii Super 13 had higher total revenue (TR), gross margin (GM), net profit (NP), return on investment (ROI) and benefit cost ratio (BCR) compared to SUWAN-1-SR. Both NPK types had similar total variable cost (TVC) and total cost (TC) but NPK 20:10:10 had higher yield quantity (Q), TR, GM, NP, ROI, and BCR than NPK Mg 12:12:17: 2. Plants treated with NPK applied at 600 and 800 kg ha-1 had the best TR, GM, NP, ROI and BCR. In experiment II, agrolyser application improved growth and yield. ROI and BCR were maximized for plants treated with agrolyser rates of 1.6 and 2.4 kg ha-1 . In experiment III, results revealed that NPK application enhanced crop growth, grain yield, NUE, nutrient content, uptake, and profitability. Grain yield and quality improved when NPK was supplemented with agrolyser. Higher number of plants per stand reduced plant growth, increased LAI, grain yield, nutrient uptake and profitability. Profitability was maximized when three plants per stand were treated with 600 kg ha-1 NPK 20:10:10 and 1.6 kg ha-1 agrolyser supplement. This combination produced the highest ROI and BCR, and is therefore suggested for adoption by maize producers (Oba Super 13) in ultisol environments.
