The potential of nutrient cycling in cover plants in response to phosphate fertilization

Residues of crops and cover crops contain considerable amounts of phosphorus (P) in their tissues, which through their mineralization can meet much of the requirement of crops. In this context, the present study aimed to evaluate the biomass production, P absorption and use of different cover crops subjected to phosphate fertilization, and its effects on the absorption and use of nitrogen (N), phosphorus (P) and potassium (K). The experiment was conducted in a protected environment from August to December 2019. The experimental design was completely randomized, arranged in a 7 x 3 scheme, consisting of the planting of seven species of cover crops (Crotalaria spectabilis, Crotalaria breviflora, Crotalaria ochroleuca, Mucuna aterrima, Mucuna pruriens, Dolichos lablab and Canavalia ensiformis), three P rates (0, 80 and 160 kg ha-1 of P2O5) and four replicates. At the time of full flowering, the cover species were cut and divided into root and shoot for subsequent determination of dry mass production, nutrient content and absorption efficiency and nutrient utilization. The results showed that Canavalia ensiformis promoted higher yield of shoot fresh and dry mass, P content in the shoots and higher N and P absorption efficiency. N and P contents in Dolichos lablab roots were higher at the highest P rates (160 kg ha-1 of P), without close relationship with the supply of shoot dry mass. The P dose of 160 kg ha-1 had an increasing and significant effect on the production of shoot fresh mass and dry mass, N, P and K contents in the shoots, N, P and K contents in the roots and efficiency of N, P and K use by the different cover crops. The P rates of 80 kg ha-1 increased the N, P and K contents in the shoots of Crotalaria ochroleuca, Crotalaria breviflora and Crotalaria spectabilis; and at higher P rates, there was a reduction in nutrient accumulation. The species Mucuna pruriens and Mucuna aterrima were efficient in the use of N, P and K at P rates of 160 kg ha-1.