Comparative effects of organic manure and inorganic fertilizer as nitrogen sources on leaf nutrient content and nitrogen use efficiency of cotton

A field experiment was conducted at the Research Farm of the College of Agriculture Jalingo, Taraba State in two planting seasons (2020 and 2021) to determine the influence of nitrogen sources and rates on nutrient concentration in leaf and nitrogen use efficiency of cotton. The experiment was a 5x4 factorial of four nitrogen sources (poultry manure, organo-mineral fertilizer, urea and NPK15:15:15) and five N rates (0, 150, 200, 250 and 300 kg/ha), laid out in a randomized complete block design (RCBD) in the field. Soil pH, organic C, N, exchangeable bases, CEC and base saturation were determined before planting. Nitrogen, K and P contents of the plant leaf increased with increasing N rate. Sources of nutrients increased the N concentration of the plant leaves. Nitrogen uptake increased with N application rate. However, at 300 kg N ha-1, N uptake decreased. Agronomic, internal use and recovery nitrogen efficiencies (aNUE, iNUE and NRE) decreased with increasing N rate. The highest value of N uptake, NRE and aNUE were obtained under NPK-treated plots, while iNUE and physiological nitrogen use efficiencies (pNUE) were at maximum under poultry manure amended plots. Cotton N use efficiency can be improved through conscientious use of fertilizers taking into consideration the soil nutrient status. Among the nitrogen sources, urea produced the lowest value for the nitrogen use efficiency of cotton. It is therefore, recommended that nitrogen dose of 150 kg/ha from either poultry manure or NPK be applied for optimum N use efficiency in the study area.