Evaluation of Nutrient Uptake of Selected Cover Crops and Biochar on the Yield Advantage of Two Taro (Colocasia esculenta) Cultivars in Samoa

A study was conducted in three agro ecological zones of Samoa to compare the dry matter yields and nutrient uptake of selected tropical cover crops and biochar application on different Samoan inceptisols. Subsequent improvements in corm yield of the two taro cultivars, (Samoa 1 and Samoa 2), under these fallow systems were also determined. The split-plot arrangement with main plots as cover crops and subplots as the cultivars was used, with four replications. The evaluated cover crops included: a reference – grass fallow treatment (farmers practice), Mucuna pruriens, Erythrina subumbrans, Mucuna pruriens + 200 kg of NPK fertiliser (12-5-20), farmer’s reference practice + 400 kg of NPK fertiliser (12-5-20), and biochar produced from coconut shells. The biomass samples were collected after the six month of fallow duration. Plant tissue analyses revealed that the nitrogen and the phosphorus contents of erythrina was higher than corresponding mucuna cover across all three sites. However, as a result of higher biomass production, Mucuna pruriens showed the highest nutrient accrual over the six month fallow duration. The general yield trend under different fallow practices across all the sites indicates that mucuna with modest supplementation of complete fertilisers can help maintain optimum taro yields. However, it appears that the yield responses of the taro crop to fallow treatments are site-specific.