| Abstract |
Nutrient uptake dynamics provide information in refining fertilizer recommendation for cassava. This study indicated that planting dates had a greater impact on the quantities, rates of nutrient accumulation as well as nutrient harvest index (NHI) and nutrient use efficiency for yield (NUEYI), but water regimes had a significant effect on these traits for the crop planted in the early rainy season (ERS) only. In the ERS, nutrients accumulated rapidly at early to mid-growth stages, but rapid accumulation occurred at mid to late growth stages for the cassava planted in the post rainy season (PRS). The total nutrient uptake was greater in the ERS than that of the PRS especially for irrigated crops. It was also noted that supplemental irrigation at mid to late growth stages for the ERS increased the total nutrient uptakes, NHI, NUEYI and yield, but irrigation had no significant effect on these traits for the cassava planted in the PRS. However, cassava planted in the PRS had higher yield, nutrient accumulation in storage roots, NHI and NUEYI than that of the ERS for both irrigated and rainfed conditions for most nutrients. Overall, total nutrient uptakes (g per plant) varied between planting dates and water regimes, and the ranks of total nutrient uptakes in descending orders were N (22.8-38.3)> K (26.0-33.3)>Ca (11.4-20.2)>Mg (4.0-7.1)>P (4.2-7.6)> S (1.2-2.5). Whereas the removal of nutrients by storage roots were as follows: K (44-64%)>N (33-40%)>P (27-41%)>S (23-48%) >Mg (17-37%)>Ca 11-19% comparing to total nutrient uptakes. |
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