Monitoramento do potássio em um cultivo de pimentão irrigado em região semiárida

Abstract

The bell pepper is of high importance within the vegetable crops, thus becoming an alternative source of income for small producers and family farms. Potassium is the nutrient most absorbed by bell pepper and diffusion the main transport mechanism to the roots, although the mass flow can have significant contribution in the process under high potassium concentration in soil solution. Predict studies for demand and leaching of crop nutrient are usually carried out sampling soil solution using solution extractors fitted in porous capsule, in which the solution is directly obtained in the field applying vacuum. This study was conducted at Nossa Senhora do Rosário Farm in Pesqueira/Pernambuco, 230 km from Recife, bearing the BR-232 road, with the objective of monitoring potassium in irrigated bell pepper crops in semiarid region. The experiment was carried out in an open field on a plot belonging to a family farmer. The seedlings of bell pepper (Capsicum annuum L.) were acquired for a specialist, using the commercial hybrid Rubia, from Sakata. The cultivation was carried out under drip irrigation, using the side lines of the system ussing a self-compensating model Katif 3.7 L h -1 per plant. The treatments consisted of four irrigation levels (L1 = 0.8 ETc, L2= 1.0 ETc, L3 1.1 Etc and L4 = 1.2 ETc) and four potassium doses (K1 = 80, K2 = 100, K3 = 150 and K4 = 200 kg ha-1 K2O), totaling 16 treatments with three plants per plot spaced 0.5 m x1.0 m between plants. The statistical design was completely randomized in a split plot with four replications, with treatments arranged in a factorial 4x4 with 64 plots. The results pointed out a slight reduction in potassium (K+) concentration and high reduction in electrical conductivity (EC), 26.3 mg L-1 and 0.21 dS m-1 in the water table, respectively. The growth variables plant height and diameter fitted to linear and quadratic models. The fresh and dry weight of shoot were influenced by irrigation levels fitting to a quadratic regression model, with maximum values of 142.64 and 23.92 g plant-1, to sheets of 103 and 104% of crop evapotranpiration (ETc), respectively. Mean values of potassium was 25.04 g kg-1. The risk of potassium contamination was observed from the output of this element of the soil layer of 0- 60 cm, with amounts higher than those used in fertilization.