Siose, Taniela K. and Kader, Md. Abdul
(2021)
Determination of optimum level of NPK for cultivation of sweetpotato in Samoa.
Journal of South Pacific Agriculture, 24
.
pp. 12-22.
ISSN 1018-7774
Abstract
Establishment of a sound fertiliser dose is necessary for achieving higher yield, soil fertility protection and environmental sustainability. Currently, there is no data pertaining to the optimum fertiliser requirement for sweetpotato under Samoan situation. To achieve this, an experiment was conducted to determine the optimum NPK levels for three sweetpotato cultivars under screen-house and field conditions in Samoa. The experiment includes four levels of NPK in kg/ha equivalent (control, 30:30:30, 60:60:60, and 90:90:90) and three improved sweetpotato cultivars (IB/PH/03, IB/PR/12, and IB/PR/13). Results revealed that each cultivar exhibited remarkably varied responses to NPK levels. Yield of IB/PH/03 increased consistently with increasing NPK levels indicating that, the applied NPK levels was insufficient to determine optimum NPK level. Cultivar IB/PR/13 followed a typical crop response curve, however, IB/PR/12 failed to produce significantly higher yield with increased level of NPK. Based on a quadratic model, the putative optimum NPK level for IB/PR/13 and IB/PR/12 was determined - 49-49-49 and 42-42-42 kg/ha respectively, however, the most profitable NPK levels were 30-30-30 and 18-18-18 kg/ha, respectively. Although the profitable NPK level was the highest level for IB/PH/03, it has not been possible to determine the optimum NPK level correctly. Thus, further studies are suggested to test higher NPK dose for IB/PH/03 and other varieties of sweetpotato under wider soil conditions in order to verify the result. This study would be a good basis for future study in a wide range of sols in Samoa and sweetpotato cultivars to achieve conclusive findings.
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