Fontes e doses de fósforo no cultivo de milho em condições de terra firme em Manaus-AM

Abstract

The study aimed to determine the best source and dose of phosphorus (P) for corn grown on land in Manaus, Amazonas, in Dystrophic Yellow Latosol. The experiments were performed in the Experimental Area km 29 of Embrapa Western Amazon in Manaus, in the years of 2012/2013 and 2013/2014, under a randomized block design in a factorial design with 10 treatments (5x2) and four repetitions, composed by two sources of P (triple superphosphate - TSP and Arad reactive rock phosphate - RRP) and five doses of P2O5 (0, 40, 80, 120 and 160 kg ha-1 of P2O5). The corn genotype used in the experiments was the double hybrid AG 1051. In the two years of cultivation, the P content was evaluated in the soil during the stages of sowing, of flourishing and of post-harvest; moreover, the P content evaluated in leaf tissue in the flowering period, in the shoot, in grain, shoot dry matter, cob length, cob diameter, cob weight, grain yield and number of sweet corn cobs besides the nutrient absorption efficiency by the plant, fraction of the total nutrient in the plant that is translocated to grains, grain yield per the unit grain nutrient, the nutrient use efficiency for grain yield and grain yield of the amount of P supplied from the fertilizer applied. Analysis of variance in the data was performed using the F test and regression analysis of quantitative data regarding P level was performed. From the detection of significant differences between treatments and their interactions, there were developments and the averages were compared between through the Tukey test at 5% probability. The maximum dose of efficiency was estimated through derivation of the regression equation. Analyzing the results, it was concluded that the use of phosphate fertilizer, regardless its font, was efficient in all researched varieties. In the two years of cultivation and in the two sources of P evaluated grain yield showed a linear behavior. The triple superphosphate source provided better grain yield in the first year of cultivation, while in the second year Arad reactive rock phosphate had and equivalent yield compared to the triple superphosphate. The best P2O5 dose for the production of sweet corn ears with no straw for marketing in the first year of cultivation was 120 kg ha- 1 of P2O5 with triple super phosphate and Arad reactive rock phosphate sources, while in the second year of growing the best dose was 80 kg ha-1 of P2O5 for triple superphosphate source and 160 kg ha-1 of P2O5 for Arad reactive rock phosphate. Regarding P absorption efficiency for corn in dry land conditions, the results show that up to 80 kg ha-1 of P2O5 available in the soil with TSP and RRP as a source, the greater the absorption efficiency by corn will be in the 1st and 2nd year of cultivation