Feijão guandu adubado com fosfato natural e utilizado como adubo verde para o cultivo de milho em latossolo de Cerrado

Abstract

The cerrado soil has major limitations in the availability of phosphorus to plants, requiring the management of mineral fertilizers and green manure. Thus, the objective was to: a) evaluate the pigeonpea, fertilized with phosphorus sources, lime and inoculated with rhizobia, as green manure in cerrado Oxisol b) verify the relative agronomic efficiency of reactive natural phosphate with that of triple superphosphate; c) assess the availability of nutrients in the soil, after incubation of biomass of pigeonpea d) to study the residual effect of pigeonpea as green manure in SPAD index and the productive characteristics of corn grown in succession. The study was conducted in a greenhouse in a design was completely randomized in 3x2x2 factorial with six replications. Phosphorus sources were evaluated: triple superphosphate, reactive natural phosphate and treatment without phosphorus, presence and absence of lime, and the presence and absence of inoculation. The seeds of pigeonpea cv. BRS Mandarin were inoculated with mixtures of two strains of Bradyrhizobium japonicum, and cultured for a period of 107 days after sowing. The variables analyzed were: number of leave, SPAD index, nodule number, dry weight of nodule, shoot and root. The land was returned to the vessels of their respective treatments. The plant material was ground, and 5 grams were taken samples of the dry mass of shoot and root portion for the determination of macronutrient (N, P, K, Ca, Mg and S). The other samples were returned to the pots and incubated for 90 days. After this period, samples were taken from 200 g of soil to determination of macronutrient (K, Ca, Mg and S). Then, we performed the seeding of the corn hybrid AG 1051 grown for 60 days after sowing. The variables analyzed were: SPAD index, shoot dry mass and root. The pigeonpea is directly influenced by phosphorus fertilization and liming in cerrado Oxisol. The reactive rock phosphate, compared to superphosphate has good agronomic efficiency. The availability of nutrients in the soil is greater with pigeonpea fertilized with triple superphosphate in the presence of lime and inoculated with rhizobia. Best match of dry matter production of16 maize shoots is obtained with triple superphosphate in the presence and absence of lime. Best match of dry matter production of corn root is obtained with triple superphosphate and reactive phosphate in the presence of lime.