Artigo
Fruit size, mineral composition and quality of trickle-irrigated tomatoes as affected by potassium rates
Autor
Fontes, Paulo Cezar Rezende
Sampaio, Regynaldo Arruda
Finger, Fernando Luiz
Institución
Resumen
An experiment was conducted to determine the fruit size, mineral composition and quality of trickle-irrigated tomatoes as affected by potassium fertilizer rates. Six potassium (K) rates were applied as KCl, corresponding to 0, 48.4, 118.6, 188.8, 259.0 and 399.4 kg ha-1, with four replicates, following a randomized block design. Quadratic responses to K rates were observed for double extra large (diameter > 60 mm), extra large (56 to 60 mm) and large (52 to 56 mm) fruit yields. Maximum yields of these classes were achieved with K rates of 116, 190 and 233 kg ha-1, respectively. Fruit dry matter, phosphorus, sulfur and magnesium contents were not affected by K rates, but nitrate and K contents showed significant increments as K rates were increased. Vitamin C, total soluble solids, lycopene and b-carotene contents in the fruits were not affected by K rates. Increments in the K rate lowered the fruit pH and increased total acids content. Para determinar o efeito da fertirrigação com K sobre o tamanho, a composição mineral e a qualidade dos frutos do tomateiro, foi conduzido um experimento com aplicação de seis doses de K, na forma de KCl, correspondendo a 0, 48,4, 118,6, 188,8, 259,0 e 399,4 kg ha-1, com quatro repetições, distribuídas no delineamento experimental em blocos casualizados. Foram observadas respostas quadráticas das produções das classes de frutos graúdo 2 (diâmetro > 60 mm), graúdo 1 (56 a 60 mm) e graúdo (52 a 56 mm) em relação às doses de K aplicadas na adubação. As produções máximas de frutos de cada classe foram obtidas com as doses de K de 116, 190 e 233 kg ha-1, respectivamente. O conteúdo de matéria seca e os teores de P, S e Mg dos frutos não foram influenciados pelas doses de K, mas os teores de nitrato e de potássio aumentaram com o aumento das doses. Os teores de vitamina C, sólidos solúveis, licopeno e b-caroteno não foram influenciados pelas doses de K; porém, os incrementos nas doses reduziram o pH e aumentaram o conteúdo de ácidos nos frutos.