Morpho-physiological and nutritional responses of safflower as a function of potassium doses
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The efficiency of potassium fertilization on the morpho-physiology and nutrition of safflower was evaluated using different doses (0, 80, 160 and 240 kg ha−1) of potassium chloride (KCl) in a completely randomized design with four replicates. In the flowering phase, were performed morphological evaluations of plant height, number of leaves, number of branches, number of chapters and stem diameter; physiological evaluations of CO2 assimilation (A), stomatal conductance (g s), transpiration (E), internal carbon concentration (C i), water use efficiency (WUE) and carboxylation efficiency (CE), and nutritional evaluations of accumulation of nitrogen (N), phosphorus (P), potassium (K), calcium (Ca) and magnesium (Mg) in the leaves. After harvesting, the nutritional status of the grain was evaluated. The potassium fertilization favored the growth of the plants, as well as positively interfered in its physiology and in the concentration of K and N in the leaves, however, the dose 240 kg ha−1 of KCl provided lower accumulation of Ca and Mg in the leaves and lower A. All evaluated characteristics were optimized in plants fertilized with potassium in relation to the dose 0 kg ha−1 up to the maximum point, which varied from 107 to 167 kg ha−1 of KCl according to the variable response, with a subsequent decline. Therefore, the dose of 160 kg ha−1 of KCl can be recommended for cultivation of safflower in soils with low level of K.