Influence of phosphorus fertiliser blends on grain yield, nutrient concentration, and profitability of soyabeans in the southern Guinea Savannah of Ghana

We conducted on-farm trials in the southern Guinea savannah of Ghana in 2016 and 2017 to evaluate soyabean response to three fertiliser blends to guide farmers towards profitable adoption of appropriate phosphorus fertiliser blend for improved soyabean production. Old Yara Legume, New Yara Legume and Triple Superphosphate fertiliser blends were evaluated. In both years, the phosphorus fertiliser blends were evaluated in a Randomised Complete Block Design with 20, 30, and 40 kg P ha−1 application rates together with control. Phosphorus fertiliser application increased soyabean yields by 1 070 kg ha−1. In 2016, fertiliser blend use efficiency ranged from 2.9 kg grain per kg fertiliser blend applied with the New Yara Legume applied at 40 kg P ha−1 to 7.4 kg grain per kg fertiliser blend applied with the Triple Superphosphate applied at 40 kg P ha−1 with significant differences between treatments. In 2017, blend use efficiency ranged from 2.5 kg grain per kg fertiliser blend applied with Old Yara Legume applied at 40 kg P ha−1 to 9.2 kg grain per kg fertiliser blend applied with the Triple Superphosphate applied at 40 kg P ha−1 with significant differences between treatments. However, phosphorus use efficiency did not significantly differ between the different treatments both in the 2016 and 2017 trials. In both 2016 and 2017 trials, the highest benefit cost ratio was attained at the lowest application rate for all the three fertiliser blends suggesting the need to review the current application rate of 30 kg P fertiliser ha−1 promoted in northern Ghana. Furthermore, the provision of credit and/or subsidy for farmers by the government is required to enable uptake and utilisation of fertilisers by farmers.