Cow Dung and Rice Husk Biochar Types as Phosphorus Sources for Cowpea (Vigna Unguiculatal.) Production in a Calciustert.

Abstract

Production of cowpea (Vigna unguiculata L.) in Ghana has relied heavily on inorganic sources of phosphorus. However, with dwindling sources of the apatite rock worldwide, the high cost and associated contamination of inorganic P fertilized soils, it has become necessary to explore more sustainable sources of P for cowpea production. Traditionally, most P fertilizer trials have been concentrated on soils with low activity clays with little work done with heavy soils. A study was therefore carried out to explore the potential of using cow dung and rice husk biochar types, as a sustainable P amendment for improved cowpea growth and yield in a Calciustert. The study evaluated the effects of cow dung biochar (CDB) and rice husk biochar (RHB) in comparison with triple superphosphate (TSP) on cowpea growth parameters and yield in Akuse Series. Twenty-four ridges were formed on the Akuse Series after determination of the soil’s standard phosphorus requirement (SPR). The CDB and RHB prepared on site at the Soil and Irrigation Research Centre (SIREC) of the University of Ghana, Kpong was then applied to 16 of the ridges; four each at the full SPR of the soil and another four each at half the SPR. There were four ridges with no amendment and another four ridges with TSP application at the SPR of the soil. All the treatments were in a randomized complete block design. The cowpea variety California Black Eye was sown on the 24 ridges at a spacing of 60 cm x 40 cm. Two weeks after sowing, the TSP at the full SPR treatment was imposed. Cultural practices were undertaken and data including average plant height to maturity, days to 50% flowering, number and weight of nodules, number of pods per plant, 100 seed weight and yield per hectare, biomass per plant at harvest, root length and mass, root and shoot P and N uptake, were taken. The experiment was repeated for another season to validate the results of the first. Cowpea plants grown in soil amended with CDB at the full SPR had the highest yield of 2.75 and 2.14 tons/ha for the two seasons compared to 2.1 and 1.86 tons/ha for the TSP fertilized crops. All the crop parameters determined were generally higher in the CDB amended ridges at the SPR of the soil than from the other treatments. Crop parameters including yield of cowpea in the other amended ridges did not significantly differ from those in the un-amended ridges. The study concludes that biochar produced from cow dung has the potential of improving growth and yield of cowpea grown on ridges in a Calciustert at SIREC when applied at the SPR of the soil. It also concludes that the soils at SIREC should not be fertilized with TSP for cowpea production as there will be no response. Further research is recommended to determine the profitability or otherwise of using CDB applied at the SPR of the soil in growing cowpea for increased yield on the Calciustert at SIREC.