Physiological and production performance of maize and soybean in crop-livestock-forest integration system under hydrogel rates and nitrogen and potassium topdressing

Water availability affects nutrient absorption and transport in plants, which is a limiting factor for production of annual crops in croplivestock-forest integration system. Thus, the objective of the present work was to evaluate the effects of hydrogel rates combined with topdressing in a crop-livestock-forest integration system on physiological and production variables of maize and soybean plants grown intercropped with forage (Panicum maximum cv. BRS Kenya) and eucalyptus (Eucalyptus urograndis). The experiments were conducted at the School Farm of the Federal Institute Goiano, Ipora campus, Goias, Brazil, in a Typic Dystrudept. A randomized block experimental design was used, in a split-plot arrangement with four replications. The plots consisted of five hydrogel rates based on the rate recommended by the manufacturer: 0 kg ha(-1) (0%), 7.5 kg he (50%), 15.0 kg ha(-1)' (100%), 22.5 kg ha(-1) (150%), and 30.0 kg ha(-1) (200%). The subplots consisted of presence and absence of nitrogen topdressing for maize, and potassium for soybean, with application of 120 kg ha(-1) of nitrogen (urea) and 60 kg he of K2O (potassium chloride). The crop systems were arranged in two experiments; experiment I consisted of eucalyptus intercropped with maize grown simultaneously with forage; experiment II consisted of eucalyptus intercropped with soybean, and the forage species grown in succession (post-harvest of soybean). Physiological variables of maize and soybean plants at the preflowering stage were analyzed. The treatments for maize crop affected the stomatal conductance, flavonoids, proline, and silage dry weight. The treatments for soybean crop had significant effects on relative water content, flavonoids, proline, and number of plants. The hydrogel rate of 7.5 kg ha(-1) (50%) resulted in positive results for both crops.