Salinidade da água, supressão da irrigação e adubação mineral e orgânica na cultura da beterraba em ambiente protegido

Abstract

Water stress associated with saline stress limits the productivity of agricultural crops, causing losses in cultivated areas. In this sense, irrigation and fertilization management appear as alternatives to minimize the effects of water and saline stress on crops. Therefore, the objective of the present study is to evaluate the effect of irrigation with saline water on the productivity and quality of tuberous roots of beet crops subjected to different irrigation suppression and forms of fertilization. The experiments were conducted in a greenhouse in the experimental area of the Auroras Seedling Production Unit (UPMA), belonging to the University of International Integration of Afro-Brazilian Lusofonia (UNILAB), Campus das Auroras, Redenção, Ceará. The design used in Experiment I was completely randomized (DIC) in a 5 × 2 factorial arrangement, with 5 replications, with the first factor corresponding to five intervals of irrigation suppression (IS 1 - No suppression interval (control); IS 2 - Suppression interval from 20 to 35 days after sowing - DAS; IS 3 - Suppression interval from 35 to 50 DAS; IS 4 - Suppression interval from 50 to 65 DAS; IS 5 - Suppression interval from 65 to 80 DAS and the second factor two salinity levels of irrigation water (A1 - 0.8 dS m-1 and A2 - 6.2 dS m-1).The design used in Experiment II was completely randomized (DIC) in 4 × 3 factorial arrangement, corresponding to four levels of electrical conductivity of irrigation water (ECa): (0.8; 2.2; 4.2 and 6.2 dS m-1), and three forms of fertilization: F1 - No fertilization (control); F2 - Mineral fertilization (NPK) and F3 - Organic fertilization (Biofertilizer), with 6 repetitions. The variables evaluated were diameter of the tuberous root (DRT), length of the tuberous root (CRT), mass of the tuberous root (MRT), soluble solids (SS), hydrogen potential (pH) and productivity (PROD). In experiment I: Water and saline stress affected the variables root diameter and pH, due to different intervals and electrical conductivity of the water, however with less intensity when irrigated with water of 0.8 dS m-1. The suppression of irrigation in the IS3 interval (35 to 50 DAS) provided a reduction in the production variables of the beet crop grown in pots. In experiment II: Organic fertilization with biofertilizer provided a better response to the variabls diameter and length of the tuberous root, with mineral fertilization with NPK being similar to the control treatment. Saline stress negatively affects root mass, productivity and pH in beet crops depending on saline levels and forms of fertilization, with less intensity with the application of bovine biofertilizer.