The objective of this research was to quantify under field conditions, the accumulation of macronutrients by onion 'Optima', in cultures established by direct sowing. The experiment was carried out at Rio Doce farm between the municipal districts of Itobi and São José do Rio Pardo, São Paulo State, Brazil. Samples were taken at the 30, 50, 70, 90, 110, 130 and 150 days after sowing (DAS), for dry mass determination and accumulation of N, P, K, Ca, Mg and S. The maximum estimated accumulation of shoot and bulb were of 5.70 g plant-1 (2.394.0 kg ha-1) and 13.17 g plant-1 (5.531.4 kg ha-1), respectively, at 150 DAS. At the end of the cycle, the average contribution of shoot and bulb were about 30% and 70%, respectively. The nutrients N, P, K and S, were accumulated preferably in the bulb; while Ca and Mg, in the aerial part. The nutrients in decreasing order of accumulation verified for the onion 'Optima' were: K > N > Ca > S > Mg > P. For a population of 420.000 plants ha-1 and a productivity of 72 t ha-1, and considering the observed values, it was verified that the onion 'Optima' hybrid exported by bulb 35.0; 5.3; 68.9; 25.8; 5.6 e 21.9 kg ha-1, respectively, of N, P, K, Ca, Mg and S.
Allium cepa L.; growth; plant nutrition
