Potassium (K) is the nutrient absorbed and exported in greater amounts by cassava crop. However, in sandy soil the K can be more easily lost by leaching, and in these soils the cassava response to K application is greater. However, considering that cassava has long cycle and slow initial growth, it may be that K application only in the planting of the crop is not sufficient to ensure satisfactory yields, especially in sandy soil conditions. Thus, the objective of this study is to evaluate the effect of rates and forms of split applications of K on yield and quality of the tuberous roots of sweet cassava grown in sandy soil. The experiment will be conducted in the experimental design of randomized blocks, in a factorial scheme 3x4+1, with four replications. The treatments will consist of 3 rates of K2O (45, 90 and 180 kg ha-1) combined with four forms of split application of K (1-100% at planting, 2 - 1/2 at planting and 1/2 at 45 days after the planting (DAP), 3 - 1/2 at planting and 1/2 at 90 DAP; 4 - 1/3 at planting, 1/3 at 45 DAP and 1/3 at 90 DAP), as well the control treatment without K. The harvest of sweet cassava crop will be performed at the end of 10-month cycle. They will be assessed: a) leaf analysis; b) number and diameter of the stems, number of leaves per plant and plant height; c) Final plant population; d) number, length, diameter and average weight of tuberous roots; e) yield of tuberous roots; and f) quality of tuberous roots. The data will be submitted to analysis of variance. The effects of the forms of split application of K will be evaluated by t test (DMS) (P <0.05), while the effects of K rates will be evaluated by regression analysis.
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