Uso da microlisimetria na quantificação do consumo hídrico da cultura do milho sob irrigação com águas salinas

Abstract

Due to the recurring water shortages in the Northeast of Brazil, brackish water is used to irrigate crops. The use of this type of water can cause damage to plants, as well as reduced water requirements as the level of saline stress increases. In experimental activities, a level of brackish water equivalent to the crop's evapotranspiration is often applied, resulting in wasted water and significant leaching. In order to determine this reduction, microlysimetry is a suitable tool. The aim was therefore to investigate, using microlysimetry, the reduction in the amount of water demanded by the maize crop as a result of the application of different brackish waters, as well as the resulting variations in its biomass production and its morphological and physiological aspects during its vegetative phase. The experiment was carried out at the UFC Agrometeorological Station in Fortaleza-CE, using the BRS 3046 maize cultivar. The experimental design was a randomized block design, with five treatments and four replications, witht two pots per repetition, for a total of 40 pots adapted to microlysimetric conditions. The treatments consisted of using brackish water for irrigation with five different electrical conductivities (S1, 1.0, local well water; S2, 1.5; S3, 3.0; S4, 4.0 and S5, 5.0 dS m-1). From 10 days after sowing (DAS), the different waters were used and the daily quantification of water requirements per treatment began. At 30 and 56 DAS, the following characteristics were assessed: plant height (AP), stem diameter (DC), net photosynthesis (A), transpiration (E), stomatal conductance (gs) and internal CO2-Ci concentration. At the end of the experimental cycle (56 DAS), the green and dry masses of the aerial part (MVPA/MSPA), the green and dry masses of the root system (MVSR/MSSR) and the total water consumption (CHT) of the corn plants were evaluated. For each unit increase in water salinity (dS m-1) there was an estimated 13.35% reduction in the total water consumption of the corn plants. The increase in the electrical conductivity of the irrigation water caused reductions in the morphological and physiological variables of the maize crop during its vegetative phase, with a consequent reduction in biomass production.