Combined Application of Inoculant, Phosphorus and Potassium Enhances Cowpea Yield in Savanna Soils

Obianuju Chiamaka Emmanuel,Francis Marthy Tetteh,Olayiwola Akin Akintola,Olubukola Oluranti Babalola

doi:10.3390/agronomy11010015

Obianuju Chiamaka Emmanuel, Francis Marthy Tetteh + Show 2 more

Open Access

https://doi.org/10.3390/agronomy11010015

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Abstract

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 Bradyrhizobia 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 Bradyrhizobia 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 Bradyrhizobia inoculant, phosphorus (0, 30, 40 kg P2O5 ha−1) and potassium (0, 10, 20, 30 K2O ha−1). Application of Bradyrhizobia inoculant with 30 kg P2O5 ha−1 and 20 kg K2O ha−1 gave the highest grain yield (1.68 and 1.86 tons ha−1) at both soils which did not differ from the yield obtained from BR-40-30 kg ha−1 P2O5 and K2O ha−1 on the Ferric Lixisol and BR-40-20 kg ha−1 P2O5 and K2O 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 Bradyrhizobia inoculant followed by P and K fertilizer was effective for cowpea growth in field conditions.

Highlights

Cowpea is a major staple food consumed in Ghana as it contributes to the protein, vitamins and minerals intake of households
The combined application of Bradyrhizobia inoculant with 30 and 40 kg P2 O5 ha−1 while omitting K2 O increased dry matter yield (29% more than control for the Ferric Lixisol and 25% for the Ferric Luvisol) which did not differ statistically to the weight produced by plants that received Bradyrhizobia inoculant only (Table 2)
This study evaluated the effect of inoculating cowpea with Bradyrhizobia inoculant together with P and K fertilizer at 2 soils of the Savanna zones of Ghana (Table 2)

Summary

Introduction

Cowpea is a major staple food consumed in Ghana as it contributes to the protein, vitamins and minerals intake of households. Constraints to cowpea production in Ghana are related more to its management than suitable variety [2] This is evident as there are improved cowpea varieties appropriate for different agroecological zones of Ghana [3]. Some of these varieties have been estimated to have a potential yield of about 3 tons ha−1 for high rainfall regions and about 2 tons ha−1 for drier regions [4]. These improved varieties did not live up to expectation, in terms of yield, in the investigated area. It was reported to require less nitrogen fertilizer application (between 15–30 kg ha−1 ) as it can fix nitrogen through a symbiotic association between its root nodules and Bradyrhizobia [6]

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