Combined Application of Inoculant, Phosphorus and Potassium Enhances Cowpea Yield in Savanna Soils
2020
Obianuju Chiamaka Emmanuel | Olayiwola Akin Akintola | Francis Marthy Tetteh | Olubukola Oluranti Babalola
Low soil phosphorus levels in savanna soils of Ghana limit cowpea response to inoculation. A two-year experiment was carried out on 2 soil types of the Guinea and Sudan savanna zones of Ghana based on the hypothesis that <i>Bradyrhizobia</i> inoculant (BR3267) in combination with phosphorus and potassium fertilizer will significantly increase cowpea root nodulation, growth and yield. The study aimed to determine the effect of phosphorus and potassium fertilizer on cowpea response to <i>Bradyrhizobia</i> inoculant. The treatments were laid out in Randomized Complete Block Design, replicated four times. The plot size was 8 × 3 m, with the sowing distance of 60 × 20 cm. The treatment comprises of commercial <i>Bradyrhizobia</i> inoculant, phosphorus (0, 30, 40 kg P<sub>2</sub>O<sub>5</sub> ha<sup>−1</sup>) and potassium (0, 10, 20, 30 K<sub>2</sub>O ha<sup>−1</sup>). Application of <i>Bradyrhizobia</i> inoculant with 30 kg P<sub>2</sub>O<sub>5</sub> ha<sup>−1</sup> and 20 kg K<sub>2</sub>O ha<sup>−1</sup> gave the highest grain yield (1.68 and 1.86 tons ha<sup>−1</sup>) at both soils which did not differ from the yield obtained from BR-40-30 kg ha<sup>−1</sup> P<sub>2</sub>O<sub>5</sub> and K<sub>2</sub>O ha<sup>−1</sup> on the Ferric Lixisol and BR-40-20 kg ha<sup>−1</sup> P<sub>2</sub>O<sub>5</sub> and K<sub>2</sub>O on the Ferric Luvisol. The same treatment also gave the highest nodule number and nodule dry weight. The results of this study have shown that the application of <i>Bradyrhizobia</i> inoculant followed by P and K fertilizer was effective for cowpea growth in field conditions.
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