Optimizing Nitrogen Rates and Plant Density for Cotton Cultivars (Gossypium spp.) in the Nigerian Savanna

Cotton production in Nigeria has been severely limited by low or blanket nutrient (especially nitrogen, N) input and poor crop management, involving use of low yielding varieties and sub-optimal plant spacing. Field experiment was conducted during the wet season (June-October) of 2013 at two locations within the Research Farm, College of Agriculture, Jalingo (longitude 11° 09’ and 11° 30’ East and latitude 8° 17’ and 9° 01’ North) to determine the (i) adaptability of three improved cotton cultivars to local climates, (ii) appropriate rate of N for optimizing cottonseed yield and (iii) optimal plant density for economic yield. The experiment was a 4 x 3 x 2 factorial arranged in a randomized complete block design (RCBD) replicated three times. The treatment combinations consisted of four nitrogen (N) rates (0, 120, 150, 200 kg ha-1), three cotton varieties (Jalingo Local, Samcot-13, Sketch-8) and two plant densities [75 x 30 cm or 44,444 plants ha-1 and 60 x 30 cm or 60,000 plants ha-1]. Data were collected on plant height, boll weight, cottonseed yield, biological (biomass) yield and numbers of monopodial and sympodial branches. Data collected were subjected to analysis of variance using the StatView Software and LSD (Least Significant Difference Test) at the 5% level of probability was used for comparison of treatment means. Plant height, boll weight, cottonseed yield, biological yield, monopodial and sympodial branches increased significantly (P < 0.05) with N application. The growth and yield components of cotton were optimum at 150 kg Nha-1. For cottonseed (lint and seed yield) yield per boll, Samcot-13 treated with 150 kg Nha-1 was the best. Cottonseed yield was best at 150 kg Nha-1 with Jalingo Local variety at 44,444 plants ha-1 density. Therefore, Jalingo Local sown at 44,444 plants ha-1 with application of 150 kg N ha-1 as urea in two equal splits (21 and 50 DAS) is recommended in the study area.