Balanço hídrico e catiônico no solo sob cultivo de soja, cevada e milho em ambiente protegido

Abstract

Water control in the plant-soil system comes to being of a great importance to assure maximum crop yields at a commercial scale. Uptake of nutrients by the plants is impinged upon soil water status, because macronutrients reach the roots by means of mass flux and diffusion processes. Soil cationic balance turns out to be a pivotal factor conditioning uptake of calcium (Ca), magnesium (Mg) and potassium (K). In light of the hypothesis of Ca:Mg ratio at suitable levels hinging upon soil water supply, the current research thesis aimed to scrutinize the inter-relationships between soil water supply and soil cationic balance on biological responses of soybean, barley and corn plants grown under protected environmental conditions. The statistical design was a randomized block in a factorial scheme 4 x 4 with three replications. The treatments imposed in the study at issue were comprised by four soil water supply levels as a function of fractions of crop maximum evapotranspiration (60, 80, 100, and 120% ETm) plus four soil Ca:Mg ratios (1:1, 3:1, 6:1, and 9:1). For soybean crop, two cultivars were used: IAC Foscarin-31 (conventional) and BMX Zeus IPRO (transgenic). The results obtained from the soybean crop have shown that biometric parameters along with yield components of soybean IAC Foscarin-31 cultivar were affected by either soil water status or soil cationic balance. For BMX Zeus IPRO cultivar, the majority of agronomical variables linearly escalated as a function of soil water status. For barley crop, the increment of biological parameters was linear as a function of soil water supply. For corn crop, agronomical performance and ecophysiological variables were affected by soil water status. Corn growth stages conditioned the expression of corn ecophysiological parameters. Calcium extraction by the soybean plants, IAC Foscarin 31 cultivar, plus corn crop was influenced by soil water regimes along with soil Ca:Mg ratios. For barley and BMX Zeus IPRO soybean cultivar, calcium uptake linearly increased with augments in soil water availability. Magnesium extraction by both soybean and corn plants was positively affected by soil water levels. Magnesium uptake by the barley plants was conditioned by soil water status and soil cationic balance. Potassium extracted by the soybean plants, IAC Foscarin-31 cultivar, was governed by soil water status and cation balance factors. Potassium uptake by the barley and soybean plants belonging to BMX Zeus IPRO linearly increased with increments in soil water levels. Soil cationic balance did not exert any influence on corn ecophysiological responses, as well as on the agronomical performance of soybean, barley and corn crops, whilst such response variables were explained by the soil water availability. The soil Ca:Mg ratio most suitable for obtaining the best possible biological response did not depend on soil water supply conditions under protected environment.