Growth and water consumption of physic nut under salt stress and phosphorus levels

Abstract

Soil salinity reduces the absorption of water by plants, consequently their growth and production. Aiming to evaluate the growth of the physic nut as a function of irrigation with saline water during the third year of growth, an experiment was conducted in a protected environment, adopting a randomized block with a 5 x 2 factorial design consisting of five levels of electrical conductivity of the water used for irrigation - ECw (0.6; 1.2; 1.8; 2.4 and 3.0 dS m^-1) and two levels of P₂O₅ per year (135 and 200 g per plant) and four replications. Plants were cultivated in pots of 200 L and irrigated at intervals of three days. The increase of ECw, starting from the 30th day after pruning (DAP), caused significant reduction in the variables: stem diameter, leaf number and leaf area. The leaf area and number were most affected and therefore are the best indicators to express the effects of water salinity on the physic nut. The salinity of the irrigation water interferes negatively in dry-matter accumulation in the leaves, and the mean water consumption of the physic nut is reduced by about 60% when irrigated with water with the highest ECw in relation to the lowest. Leaf area was the only growth variable influenced by phosphorus levels in the three evaluations, where leaf number was influenced at 30 DAP. This physic nut crop demonstrates sensitivity at water salinity levels above 1.6 dS m^-1.