NO ₃ ^– , K ⁺ , and chlorophyll index in fertigated grapevines in the semi-arid region of Brazil

ABSTRACT

Evaluating the effects of N and K supply on grapevines ( Vitis vinifera L.) and the techniques for nutritional diagnosis is of great importance for fertigation management of this crop. This study evaluated the effects of N and K fertigation on the soluble concentrations of NO ₃ ^– and K ⁺ in the petiole sap and on the leaf chlorophyll index in drip irrigated ‘Syrah’ grapevine (from 17 June 2013 to 25 Nov 2014). The treatments consisted of five levels of N (0, 15, 30, 60 and 120 kg ha ^–1 ) and K ₂ O (0, 15, 30, 60 and 120 kg ha ^–1 ), combined in an incomplete 5 ² factorial scheme in 13 combinations and arranged in randomized blocks with four replications. We determined NO ₃ ^– and K ⁺ concentrations in petiole sap, leaf chlorophyll index, grapevine cluster mass and number per plant, mean grapevine cluster mass, and phenolic composition. High NO ₃ ^– concentrations contributed positively to grapevine yield; however, increased K+ concentrations caused a negative response of sap. For 120 kg N ha ^–1 rate, NO ₃ ^– in the sap and chlorophyll index showed higher values at the flowering stage, while high values for K ⁺ were observed during the grape-ripening stage.

Vitis vinífera L.; fertigation; petiole