Fertirrigación con diferentes formas de nitrógeno en el cultivo de tomate en un suelo arcilloso

the effect of nitrogen form (urea, nitrate and ammonium) provided at various stages of development of the tomato crop on the yield and quality of fruit was studied. the work was conducted under field conditions in a pellustert soil, drip irrigation and a warm and semi-arid climate. three fertilization treatments (t1, t2 and control) were arranged in a randomized complete-block design with three replicates. t1 and t2 were fertilized with 250-50-190kg·ha-1 n, p and k, respectively; which n was supplied in different ratios of ureic-n, ammonium-n and nitric-n along growing tomato plants; t3 was provided in a similar way as is generally employed by the tomato producers in the culiacan valley, sinaloa, mexico (450-118-413kg·ha-1 n-p-k), with 75% of n in nitrate form. the concentration of n-no-3 in the petiole cell extract in t1 and t2 ranged from 500 to 1360ppm, and in the control it was 300-1175ppm. these values were related with the total n doses supplied but not with the ratio of nh4/no3 provided, neither influenced on the total amount of exportation fruit. the fruit production was statistically similar in the high and moderated fertilizer doses with a fertilizer savings of 75% of nitrate n. with respect to the post-harvest quality in the tomato fruit, moderated fertilization associated with high application of ureic-n and ammonium-n did not affect the fruit firmness, obrix or the weight loss in the fruit.