Organic amendments increased sweetpotato (Ipomoea batatas L.) yield in a calcareous sandy soil of Samoa

Abstract

A five-month field experiment was conducted to investigate the effects of organic amendments on yields of two sweetpotato cultivars in a calcareous sandy soil of Samoa. The treatments consisted of three organic amendments; gliricidia, gliricidia + biochar, poultry litter, and a control, and two improved sweetpotato cultivars (IB/PH/03 and IB/PR/13). All amendments were applied at equivalent rate of 100 kg N ha–1 while biochar at 5 t ha–1. Plots were arranged in a RCB design with four replicates. Results showed that all organic amendments significantly increased total storage root and marketable storage root yields, compared to yields of the control. Total marketable root yield was increased by 134, 118, and 294% over control in response to gliricidia, poultry litter, and gliricidia + biochar treatments. The highest yield, yield attributing parameters and nutrient uptake by storage root were recorded in gliricidia + biochar treatment, which appears to synergistically influence crop yield relative to organic amendments applied singly; a potential amendment for improving sweetpotato productivity in sandy calcareous soil. Cultivar IB/PH/03 performed better than IB/PR/13 on all measured crop parameters except for fresh weight of non-marketable root and percent dry matter content showing better potentiality for promotion under similar agro-environmental conditions.