Observations on Palm Bunch ash Effects on Cowpea Growth and Characteristics of a Ghana Acid Soil

Abstract

Oil palm bunch ash is a locally available material in Ghana with the potential of being used as fertilizer. A pot-experiment was conducted in a roofless open-air planthouse to study the effects of palm bunch ash on cowpea dry matter yield, tissue nutrient content and soil characteristics. Airdry palm bunch ash (with pH 10.6 and 26% K, 6.8% Ca, 5.8% Mg, 4.0% P, on oven dry weight basis) was applied to cowpea in Olin soil (a loamy sand, classified as aquic Ustifluvent) at the rates 0.0 (T0), 0.42, 0.83, 1.67, 2.50, 3.33 and 4.17 g kg soil (T6). Plants were harvested 41 days after planting and shoot and root dry matter (DM) yields were measured. Whole plant tops were analyzed for elemental contents. Ash application resulted in significant increases in DM yields steadily from Shoot increased from 5.6 (at T„) to 30.3 g and root DM from 0.9 (at To) to 3.3 g plant  application significantly increased cowpea, rom 1.2% (at To) to 10.6% (at T6) and P from To) to 0.51% (at T1)) to 0.51% (at TO, but had effect on tissue Ca and Mg. Soil analysis alter harvest showed that ash application in-creased soil pH from 4.7 (at To) to 7.2 (at T6), available P from 0.7 (at To) to 5.3 mg kg-1 (at T6), exchangeable K from 0.05 (at To) to 1.3 c mol kg-1 (at T6), and exchangeable Ca from 0.52 (at T0) to 2.17 c mol kg-1 (at T6), but decreased soil total N from 2.8 (at To) to 0.7 g kg-1 (at T6) and soil exchangeable Mg from 0.76 (at To) to 0.10 c mol kg-1 (at T6). A palm bunch ash application of 0.83 g kg-1 soil was found to be optimum for the growth of cowpea in the Ofin soil. The study showed that oil palm bunch ash has properties that can be exploited as a fertilizer particularly on acid soils.