LAUSR

The decomposition and release of nutrients from plant residues that precede the cultivation of vegetables can positively affect the morphological parameters and crop productivity. The objective of this study was to evaluate the effects of plant residue decomposition and the cycling of macro and micronutrients of four cover crops preceding the broccoli production (single head Avenger hybrid). A 4x3 factorial scheme was implemented including four cover crops: signal grass (SG), pearl millet (PM), sunn hemp (SH), mixture PM+SH; and three doses of mineral fertilizer: 0, 50 (200 kg ha-1 of P2O5, 50 kg ha-1 of K2O, 75 kg ha -1 of N) and 100% of the recommended fertilizer dose (400 kg ha-1 of P2O5, 100 kg ha -1 of K2O and 150 kg ha-1 of N). Fresh (FB) and dry biomass (DB), residue decomposition, nutrient cycling of cover crops, the number of leaves, head height (HH), stem diameter (SD), head diameter (HD), head fresh-biomass (FB), head dry biomass (DB) and broccoli yield were evaluated. The FB production from PM (25.9 t ha-1), SG (23.3 t ha-1) and mixture PM+SH (23.9 t ha-1) were similar, while the largest production of DB occurred in the SG (11.9 t ha-1). The lowest rate of decomposition and the greatest half-life time of residues occurred where PM was present. The accumulation and nutrient cycling follow the sequence K>N>Ca>Mg>P>S and Mn>Zn>B>Cu for all cover crop treatments evaluated. The highest SD (51.95; 51.44 and 50.67 mm), HD (187.97; 187.41 and 183.48 mm), FB (1.01; 1.00 and 0.97 kg), DB (0.08; 0.07 and 0.07 kg) and broccoli yield (25.3; 24.9 and 24.7 t ha-1) was observed in the 100% dose of mineral fertilizer and on the residues of SH or PM+SH mixture, respectively.