Nutrient uptake and nutrient use efficiency of cassava genotypes with different starch bulking periods as affected by different planting dates

Information on macronutrient uptake and nutrient use efficiency (NUE) of cassava genotypes under different planting dates is limited. The aims of this study were 1) to investigate the responses of cassava genotypes to planting dates for nutrient uptake and NUE and 2) to identify the superior genotypes based on these traits. Three cassava genotypes (Kasetsart 50 (KU50), Rayong 11 (RY11) and CMR38-125-77) were planted in a randomized complete block design with four replications at four planting dates (20-Apr, 30-Jun, 5-Oct and 15-Dec 2016) and harvested at 12 months after planting (MAP). Planting cassava on 20-Apr and 15-Dec produced the highest total crop nutrient uptake and nutrient uptake for storage roots. Whereas planting cassava on 5-Oct and 15-Dec with higher solar radiation, temperature, relative humidity and longer photoperiod during canopy establishment until high carbohydrates translocation and with lower temperature and shorter photoperiod during a dormancy period resulted in greater NUE for biomass and storage roots and nutrient harvest index for all genotypes and most elements. CMR38-125-77 and KU50 showed good performance in terms of total nutrient uptake across planting dates (1.45-38.31 g plant(-1)) for most elements. CMR38-125-77 seems to be the best genotype on the basis of high storage root dry weight, high NUE for both biomass (90.1-1,594.6) and storage roots (39.9-927.1) and nutrient harvest index (0.14-0.58) for almost all planting dates, except in planting date 20-Apr in which RY11 was the highest for these traits. The genotype identified is useful as parental source for further breeding programs to improve genotypes with high NUE and high storage root yield.