Nutrient uptakes and use efficiency of cassava under different moisture conditions

Abstract Precise fertilization based on crop needs is important for optimal yield and cost‐effectiveness. This study aimed to investigate nutrient uptakes in cassava under different planting dates and irrigation conditions (W). Two‐year field trials were conducted in the early (ERS) and post‐rainy seasons (PRS), with nutrient uptakes measured at five growth stages. Planting dates had a greater impact on nutrient uptakes, accumulation rates, nutrient harvest index (NHI), and nutrient use efficiency (NUE) than W. In the ERS, the nutrients accumulated rapidly at the early to mid‐growth stages, while this occurred at the mid to late growth stages for the PRS. Nutrient uptake was higher in ERS than PRS, with W differenced only in ERS 2015. Irrigation during the mid to late growth stages increased the nutrient uptake, NHI, NUE, and yield for the ERS (2015), with less impact on the PRS. In contrast, the PRS significantly improved yield, accumulation in storage roots, NHI, and NUE. Total nutrients accumulated by the whole plant (kg ha −1 ) were N (207–383) > K (182–401) > Ca (180–202) > Mg (62–82) > P (42–76) > S (11–25), Fe (2.60–7.64) > Mn (1.60–3.34) > Zn (0.48–0.62) > B (0.15–0.25) > Cu (0.11–0.19) > Mo (0.026–0.055). Nutrients with high NHI were K (0.41–0.64), Zn (0.35–0.58), N (0.28–0.56), Cu (0.16–0.61), B (0.16–0.52), and Mo (0.19–0.62), and lower NHI were P (0.27–0.47), Mg (0.17–0.37), S (0.15–0.48), Fe (0.15–0.34), Ca (0.09–0.19), and Mn (0.04–0.31). These findings will improve nutrient requirement guidelines for seasonal fertilizer recommendations for cassava in Thailand.