UPTAKE AND EFFICIENCY OF NITROGEN, PHOSPHORUS AND POTASSIUM IN MAIZE PRODUCTION AS INFLUENCED BY NEEM (Azadirachta indica L.) SOIL AMENDMENTS IN THE GUINEA SAVANNAH ECOLOGICAL ZONE OF GHANA

Abstract

The cultivation of maize (Zea mays L.) in northern Ghana is synonymous with fertilizer application, but efficient nutrient uptake and utilization are major factors that influence yield parameters and grain yield. The impact of neem cake (NC) and its oil as soil amendments on nutrient uptake and efficiency of Nitrogen (N), Phosphorus (P), and Potassium (K), as well as growth, yield components and yield of maize, was investigated. The trial was conducted at two locations, Tamale Technical University and the University for Development Studies farms in Tamale and at Nyankpala close to Tamale, respectively in northern Ghana in 2021 cropping season. This was a 2 × 3 × 3 factorial experiment with treatment arranged in a Randomized Complete Block Design with three replications. Treatments that were applied included NC with 0, 200, and 400 kg/ha, neem oil (NL) with 0, 10, and 20 l/ha, and NPK at 0 and 250 kg/ha with fertilizer grade 15:15:15, the latter and in situ nutrient in soil supported as sources of NPK. The study found increasing the rate of NC from 200 to 400 kg/ha combined with 250 kg NPK/ha increased plant height, shoot dry weight, LAI, uptake and efficiency of uptake of NPK, grain yield, and harvest index (HI) of maize. Plant height, shoot dry weight, LAI, N, P, and K uptake and uptake efficiency, grain yield and HI of the crop diminished with increasing NL rate, beginning with 10 l NL/ha to 20 l NL/ha merged with 250 kg NPK/ha. The results showed combining 250 kg NPK/ha with 10 l/ha NL boosted N uptake for maize by 7.3 % (from 150.4 kg/ha to 161 kg/ha) over the approved NPK rate in maize. P uptake in maize increased by 6.8% (from 54.5 kg/ha to 58.2 kg/ha) with 250 kg NPK/ha combined with 10 l/ha NL. When 250 kg NPK/ha was combined with 400 kg/ha NC, the percentage increase for P uptake was 28% (from 47.7 kg/ha to 61.1 kg/ha) over the control. Incorporation of 250 kg NPK/ha gave uptake efficiency of 0.036 kg N/kg, 0.056 kg P/kg, and 0.048 kg K/kg as maximum entries. NC at 400 kg/ha recorded an economic yield of 1172 kg/ha. Grain yield was positively correlated with N, P and K uptake and N uptake efficiency, but not with P and K uptake efficiency, respectively with r = 0.91**, 0.82**, and 0.85**; and 0.20*, 0.01, and 0.03. The combined data analysis showed only location by NPK interaction on the majority of parameters, which was likely due to differences in the baseline soil fertility status. The study revealed 250 kg NPK/ha combined with 400 kg NC/ha manifested explicit role for optimum N, P and K uptake and efficiency, growth and yield of maize in the Guinea savannah ecological zone of Ghana. 10 l/ha NL combined with 250 kg NPK/ha also iii was another most economical treatment and are therefore recommended for optimum N, P and K uptake and efficiency, growth and grain yield of maize in the Guinea savannah ecological zone of Ghana.