Productive and biochemical responses of Marandu grass under fertilization protocols

The aim of this study was to evaluate the effects of liming and chemical fertilization protocols, containing different combinations of nitrogen (N), phosphorus (P) and potassium (K), on the photosynthetic pigments, productive characteristics and carbohydrate concentration of Urochloa brizantha cv. Marandu. Five fertilization protocols were evaluated (PK fertilizer combination; NP fertilizer combination; NK fertilizer combination; NPK fertilizer combination; and without fertilizer - control), associated or not with soil correction via liming, in a completely randomized design, with four replicates. The experimental units consisted of plastic pots with a capacity of 12 liters, which were filled with 10 dm³ of sandy clay loam soil. Seeds of Urochloa brizantha cv. Marandu, with 80% cultural value were used. With the corrected soil, the NP protocol provided greater production of dry mass of residue (PMSRE), root volume, leaf area, leaf area index, total sugar content (AST) and starch in the root, compared to the other protocols. Without liming, the NP protocol provided greater production of aerial part dry mass (PMSPA), root volume, leaf aerial volume, leaf aerial index and AST content in leaves, roots and residue. The NPK protocol, with liming, was 73% higher in chlorophyll a content, 50% in carotenoid content, 90% in PMSPA, 78% in leaf area and 76.2% in leaf area index, compared to the soil without correction. The use of NP fertilization with liming is recommended as it provides positive responses on the photosynthetic pigments, productive characteristics and total sugar content of Marandu grass.