Manejo de aplicação de fósforo e fontes nitrogenadas na sucessão soja e milho em solos de fertilidade construída

Abstract

Has been reported in the literature that in soils with improved fertility, the phosphate fertilization can be applied in the system, fertilizing the production system instead of thinking about each one of the cultures single. On the other hand, there is a lack of regionalized information for soybean/corn production systems in central Brazil. Nitrogen fertilizers with increased efficiency are currently being launched, which have been recommended by manufacturing companies for application in the seed furrow. However, as the amounts of N used are above those recommended with conventional fertilizers, further studies are needed. The objective of this study was to compare the efficiency of conventional phosphate fertilization in the sowing soybean and corn crops, with two forms of system fertilization, in addition to verifying the best source and form of nitrogen fertilizer application in corn from second crop. The experiments were carried out independently under a randomized block design (four replications), in split plots. The main plots were constituted by the forms of application of phosphorus in the system, as follows: 1 – Fertilization system 1: application of the total P required by soybean and corn crops (115 kg ha-1 of P2O5), in the corn sowing furrow off- season; 2- Fertilizing system 2: application of total P required by soybean and corn crops (115 kg ha-1 P2O5), in the sowing furrow in summer soybean; 3- Conventional fertilization: application of P required by the soybean crop (65 kg ha-1 P2O5) in the sowing furrow in soybean and the P required by the corn second crop in the sowing furrow in corn (50 kg ha- 1 of P2O5) and 4- control - without application of P. The subplots were constituted by the sources of N, applied through different sources and forms, in the corn on second crop, being common urea in topdress; ammonium nitrate applied in topdress; Polyblen® applied in the seed furrow; Sulfammo meta 29® applied in the seed furrow and the control treatment, without N. Soil P contents, leaf N and P contents, plant height, corn cob insertion height, weight of a thousand grains, number of rows of corn cob, number of grains per row on corn cob and yield. The highest corn yield was achieved when the phosphate fertilizer required by the corn was applied or when the system fertilization was applied in the corn sowing furrow. On the other hand, the productivity of the soybean crop was not affected by the form of supply of phosphate fertilizer, making the producer's way of fertilizing the soybean crop more flexible. In the corn crop, plants that received fertilization with any source of mineral N had higher levels of leaf N, corn cob insertion height and number of rows per corn cob. Treatments that received Sulfammo® and Polyblen® fertilizers applied in the seed furrow had higher chlorophyll index, corn yield and total crop yield.