GREEN MANURE AND MINERAL FERTILIZATION: RESIDUAL EFFECT ON DRY MATTER PRODUCTION, NUTRIENT EXTRACTION AND NUTRIENTS RECOVERY EFFICIENCY IN TWO SUCCESIVE CROPS

Background. Green manures (GM) are an alternative to partially or totally replace mineral fertilizers, in successive crops, but few studies have studied the residual effect (REEF) of GM on the subsequent crops. Objective. To determine the REEF of GM ( Mucuna cinerea , sin. Stizolobium cinereum ) and mineral fertilization (MF) on dry matter production (DM), nutrient extraction (NEX) and soil solution (SS) characteristics in the Brachiaria brizantha (BB). A second objective was to determine the nutrient recovery efficiency (RE) in two successive crops of broccoli and BB. Methodology. A single application of GM snd MF was done on broccoli crop, in pots and greenhouse conditions. The treatments were: 1) unfertilized plants (Control). 2) 200% of the recommended dose for broccoli, applied exclusively through MF (MF200). 3)  GM at 10 t ha -1 (GM10). 4) The same dose of N, P, K, Ca, Mg, and S applied through GM10 was applied through MF (MF=GM10). 5) GM10 + MF to supply the same dose of N, P, K, Ca, Mg, and S supplied with MF200 (GM10+MF). After broccoli harvest, the BB was planted in the same pots, without additional fertilization. Results. In BB, greater REEF on DM, NEX (N, P, K, Ca, Mg and S), electrical conductivity and nutrient concentration (N, K, Ca, Mg and S) in SS, was detected with GM10 and GM10+MF. Considering both crops, greater DM and NEX were obtained with MF200 and GM10+MF. Higher RE of P and S was obtained with GM10, while, higher RE of K and Ca was obtained with the MF=GM10. Implications. The study shows that the efficiency of nutrients applied through GM at 10 t ha -1 , combined with low doses of mineral fertilization, increases in successive crops. Conclusion. The REEF on the DM and nutrient extraction of the BB change depending on the fertilizer type and dose used. The REEF on the SS characteristics is only detected in the initial growth phase of the BB. In successive crops, the proportion of DM produced and the amount of nutrients extracted changes depending on the species used. To obtain a similar nutrient recovery between GM and MF is necessary to consider the DM of more of one crop.