Nutritional status, yield components, and yield of cassava as influenced by phenological stages and water regimes

Water deficiency affects several important processes for the plants and, although cassava crop is known to have genotypes well adapted to drought, studies about the characteristics that may indicate tolerance or sensitivity to this abiotic stress are scarce for this crop. The objective of this research was to evaluate the nutritional responses and productive components in cassava plants, in different development stages and under different soil water tensions. The experiment was laid out following completely randomized design, composed by three growth stages, 90 to 180, 180 to 270 and 270 to 360 days after planting (DAP), and three soil water tensions (-10, -40 and - 70 kPa), with five replicates. The plants were mainly affected from 90 to 180 DAP, by soil tensions (-40 and -70 kPa), showing decreases in K and Fe levels and increases in P, Mg and Zn levels. The yield components were also affected by water deficit in this stage, with decreases in the shoot dry matter mass (61.7%), of the tuberous roots (80.4%) and of the stake (43.9%). The imposition of severe water deficit caused 100% of reduction in the diameter and length of the commercial root, in the peel thickness and in the pulp diameter. And yield was drastically affected by soil tensions -40 and -70 kPa in the third and fifth growth stages.