Trocas gasosas e crescimento de Atriplex nummularia Lindl irrigada com água proveniente de rejeito salino

Abstract

The salinity of soil and water is one of the main problems for agriculture in the arid and semiarid regions. The species of plants of the genus Atriplex (Atriplex nummularia Lindl), tolerant to the salinity and the water stress, appear as an option for the cultivation using saline wastewater of desalinizers, common in these regions, reducing the discharge of this effluent to the environment. Thus, the objective was to evaluate the effect of interaction between levels of soil moisture and irrigation water salinity, gas exchange and growth of saltbush (Atriplex nummularia Lindl). The saltbush was cultivated in pots with soils under two moisture levels (50 and 100% of the field capacity) and irrigated with waters at 0, 25, 50, 75 and 100% of saline waste, corresponding to electrical conductivities (EC) of 0,39; 1,54; 2,15; 2,79; and 3,63 dS m-1. The experiment was conducted in a greenhouse for 163 days, with a factorial arrangement of 2x5, in a randomized complete block design, with four replications. The photosynthetic, biometric and biomass parameters of the plants were evaluated. Irrigation with saline wastewater with higher EC reduced the gas exchange of saltbush plants, reducing the net photosynthetic rate, stomatal conductance, transpiration and intracellular CO2 concentration. Although it is a halophyte plant, saltbush has reduced photosynthesis with increasing EC in irrigation water (1,54-3,63 dS m-1) after 17 days. Under favorable conditions of humidity (100% of the field capacity), the increase of salt reject in the irrigation water does not interfere with the water use and carboxylation efficiency of the plants. Growth and biomass of saltbush plants are stimulated under irrigation of saline water (EC ≤ 3,63 dS m-1) when soil water content is maintained at field capacity.