Cover crop residues decomposition, nutrient cycling and doses of mineral fertilizer in irrigated broccoli production

Resumo

Abstract: The decomposition of plant residues and release of nutrients in irrigated areas cultivated with vegetables occur at a more accelerated rate. This situation can be managed to improve the efficiency of mineral fertilizers in vegetable crops. Thus, the main objective of this study was to evaluate the effects of residue decomposition and macro and micronutrients cycling of four cover crops in an irrigated broccoli production area. The experiment was conducted in factorial scheme 4x3, being four cover crops (Signal grass (SG), Pearl millet (PM), Sunn hemp (SH), PM+SH), and three mineral fertilizer doses (0, 50 and 100% of the recommended fertilizer dose: 400 kg ha^-1 of P₂O₅, 100 kg ha^-1 of K₂O, 150 kg ha^-1 of N), arranged in randomized block design with parcels of 40 m² (4x10 m), and four repetitions. Fresh and dry biomass, residue decomposition and nutrient cycling of cover crops, and the number of leaves, stem diameter, head height, diameter, fresh and dry biomass, and productivity of broccoli were evaluated. The greatest dry biomass of cover crops was observed when Poaceae plant species were present, particularly SG. The lowest rate of decomposition and the greatest half-life time of residues occurred where PM was present. The residue decomposition and nutrient cycling were at least three times faster in irrigated areas. The accumulation and nutrient cycling follow the sequence K>N>Ca>Mg>P>S, and Mn>Zn>B>Cu in all cover crop treatments evaluated. The greatest broccoli production was observed in the 100% mineral fertilizer dose and SH or PM+SH preceding broccoli crop farming.

Keywords: Brassica oleracea var. italica; Crotalaria juncea; Urochloa brizantha cv marandu; Pennisetum glaucum; NPK