The Mixture of Legumes and Gramineous as Green Manure and Its Effect on Nutrient Efficiency and Soil Solution Characteristics in Three Successive Crops

We determined the accumulation, agronomic efficiency (AE), and recovery efficiency (RE) of N, K, Ca, Mg, and S in the first broccoli crop, as well as the RE of N (NRE) and the soil solution (SS) characteristics in two subsequent crops, using different ratios (0, 25, 50, 75, and 100%) of Jack beans (JB) and pearl millet (PM). The treatments control, 100JB, 75JB25PM, 50JB50PM, 25JB75PM, and 100PM were applied only at the first broccoli crop. After the harvest, the treatment residual effect was measured in a second broccoli crop and the brachiaria grass (in four cuts). Greater nutrient accumulation, AE, and RE were detected with 100JB and 75JB25PM. Static differences in SS pH were detected in five of the 10 sampling dates, although the effect of treatments changed over time. In the SS, a higher concentration of N and K and a lower concentration of Ca, Mg, and S were detected with 100JB compared to the control. Increasing the proportion of JB in the mixture results in higher accumulation, AE, and RE of K, Ca, Mg, and S in the first broccoli crop and higher NRE in successive crops. As the proportion of PM in the mixture increases, the need for inputs that promote the mineralization process increases. Changes in SS are mainly crop-driven, except in the case of pH, EC, and nutrient concentrations which decrease as plant age and the number of established crops increase.