CULTIVO DE GIRASSOL SUBMETIDO A NÍVEIS DE REPOSIÇÃO HÍDRICA, ADUBAÇÃO MINERAL E ORGANOMINERAL

Abstract

Sunflower cultivation in the second crop "off-season", in the Midwest region of Brazil, is an important economic and ecological strategy for production system, whose knowledge of its water and nutritional needs are indispensable, due to the weather conditions at this time of the year. The first stage of this study aimed to evaluate the agronomic performance of sunflower cultivated under different conditions of water availability and fertilization levels with mineral and organomineral NPK formulations applied at sowing. The experiment was carried out in plastic pots filled with 30 liters of soil, collected from the 0.0 to 0.2 m layer, of a dystroferric Red Latosol, located in an experimental area of the Goiano Federal Institute, in Rio Verde, Goiás. The experimental design was a randomized complete block in a 4x4x2 factorial scheme with three replications. The treatments were the combinations of four water replacements, equal to 50, 75, 100 and 125% of the available water capacity in the soil; four doses of formulated 04-14-08 (NPK) referring to 50, 100, 150 and 200% of the recommendation and two sources of formulated NPK, mineral and organomineral. Water replacements were determined by electronic weighing lysimeters and water applied by surface drip system. Height, stem diameter, leaf number, leaf area, chlorophyll a, chlorophyll b, total chlorophyll and SPAD index were evaluated at 20, 40, 60 and 80 days after sowing (DAS). The inflorescence diameter was evaluated at 60 and 80 (DAS). At harvest, fresh and dry mass of leaves, stem and chapter were evaluated. The increase in water replacement provided higher plant height and stem diameter for sunflower crop. Water replacements of 125 and 103% provided the largest accumulations of leaf and stem dry matter of sunflower crop. The increase in the amount of NPK applied through the organomineral source reduced the leaves dry weight and the stem fresh weight. At the 50% dosage of NPK recommendation, the organomineral source was higher than the mineral source for leaf dry mass and stem fresh mass. The second cycle of the present work was carried out in plastic pots filled with 30 liters of soil, collected from the 0.0 to 0.2 m layer, of a dystroferric Red Latosol, located in an experimental area of the Goiano Federal Institute, in the municipality of Rio Verde, Goiás. The experimental design was a randomized complete block with a 4x2 factorial scheme with three replications. The treatment was based on four-dose applications of the formulation 04-14-08 (NPK) referring to 50, 100, 150 and 200% of the recommendation and two sources (mineral and organomineral) of NPK formulation. Growth, dry matter accumulation, water content and yield were analyzed at 30, 60 and 90 days after sowing (DAS). The inflorescence diameter was evaluated at 90 (DAS). The NPK mineral source provided greater efficiency in practically all variables analyzed.