Evaluation of sources, doses and application schedules of nitrogen on drip-irrigated tomato

Abstract

We aimed to establish strategies for nitrogen (N) fertilization on drip-irrigated determinate-growth-habit tomato, under Cerrado conditions of Central Brazil. Three field experiments were carried out in a randomized block design. In experiment I six N doses (0, 80, 160, 240, 320 and 400 kg ha-1 N) were tested, in experiment II six combinations of the N forms (nitric; ammonium; amide; 2/3 nitric + 1/3 ammonium; 2/3 nitric + 1/3 amide; and 1/3 nitric + 2/3 amide) were evaluated, and in experiment III the combination of three soil pre-plant fertilization fractions (0, 20 and 40%) was evaluated with two splitting schemes of the remaining N via fertigation (linear and adjusted N-uptake curve). SPAD chlorophyll index and N content were measured in the leaves of tomato plants on experiment I. The physical and economic yields of tomato crop were maximized for the doses of 287 kg N ha-1 and 270 kg N ha-1, respectively, with doses of 2.1 g and 2.0 g of N per kg of commercial fruit. The yield was maximized for 52 SPAD units. The combinations of forms and the application schedules of N had no significant effect on the yield components of the tomato crop.