Fertilizantes com proteção integrada: dinâmica de fósforo em solo e planta

Abstract

Tropical soils, specifically Latossols, have a marked degree of weathering, which promotes characteristics such as low availability of nutrients and high phosphorus adsorption capacity (P). Under these conditions, the soil acts as a drain and not as a source of P for the plants, with the need to apply quantities of phosphate fertilizers above the requirement of agricultural crops. However, most of the phosphate fertilizers used have low efficiency of use, due to the loss of P by adsorption, which results in low availability of P in the soil solution. In this sense, an alternative that has been studied is the use of phosphate fertilizers that contain aggregate technology that can reduce the intensity of the P adsorption phenomenon and increase the availability of P when compared to conventional phosphate fertilizers, being called in this thesis of phosphate fertilizers with integrated protection. Therefore, the objective of this thesis was to evaluate the dynamics of P in the soil-plant system from the application of phosphate fertilizers with integrated protection. To this end, four experiments were set up, which gave rise to the thesis chapters. n chapter 1, an experiment was carried out under laboratory conditions in a 2 × 3 × 3 factorial scheme, with two soils (clay Red-Yellow Latosol - LVA 1 and clayey Red Yellow Latosol - LVA 2), three phosphate fertilizers (conventional monoammonium phosphate - CONV; conventional monoammonium phosphate coated with polymer - POL; and conventional monoammonium phosphate pelleted with filter cake - ORG) and three times to reach the matric potential of -10 kPa in soils (Season 1 = the matric potential of -10 kPa in the soil was reached on the day of the addition of the phosphate fertilizer granule; Season 2 = the matric potential of -10 kPa in the soil was reached three days after the addition of the phosphate fertilizer granule; and Season 3 = the matric potential of 10 kPa in the soil was reached six days after the addition of the phosphate fertilizer granule), aiming to evaluate the availability of P after the application of phosphate fertilizers with integrated protection in different soils and times to reach the matric potential of -10 kPa. The experiment in Chapter 2 was also carried out under laboratory conditions, being evaluated the availability of P after application of phosphate fertilizers with integrated protection in different soils, matric potentials and contact times. The factors under study were two soils (LVA 1 and LVA 2), three phosphate fertilizers (CONV, POL and ORG), two matric potentials (-10 and -50 kPa) and seven contact times (1, 2, 4, 8, 15, 30 and 45 days after the addition of phosphate fertilizers). In chapter 3, the effect of applying phosphate fertilizers with integrated protection on the availability of P for corn plants was evaluated, and an experiment was carried out in a greenhouse. Two soils (LVA 1 and LVA 2), three phosphate fertilizers (CONV, POL and ORG) and two potential matric (-15 kPa and -50 kPa) were used. The experiment in Chapter 4 was carried out in the field for two years to evaluate the productivity and nutrition of Conilon coffee from the application of phosphate and nitrogen fertilizers with integrated protection. The experiment, implanted in a 3 × 2 × 3 factorial, consisted of three phosphate fertilizers (CONV, POL and ORG), two quantities of phosphate fertilizers (Q100 = 100 % of the quantity of phosphate fertilizer; Q150 = 150 % of the quantity of phosphate fertilizer) and two nitrogen fertilizers (conventional urea - UC and conventional urea covered with polymer - UP). In chapter 1, the results indicated that the application of phosphate fertilizers with integrated protection (POL and ORG) promoted an increase in the availability of P in LVA 1, indicating that the use of technology can be promising to improve the availability of P in soils with lower adsorption capacity of P. The results in chapter 2 showed that the ORG showed the smallest reductions in the levels of available P with the increase in contact times in relation to POL and CONV. The matric potentials allowed the differentiation of the phosphate fertilizers studied in the availability of P, and the ORG showed more constant values in both potential matric, demonstrating that the organic coating can be promising in maintaining the availability of P over time. In chapter 3, phosphate fertilizers with integrated protection (POL + ORG) compared to CONV increased the production of leaf dry matter (5.0 %), the leaf content of P (7.4 %) and the content of P in leaf (15.7 %) in LVA 1 and P content in xylemic sap (7.6 and 10.3 %) in LVA 1 and LVA 2, respectively. The results obtained demonstrate that phosphate fertilizers with integrated protection favored the initial development of corn plants. In chapter 4, the results showed that phosphated fertilizers with integrated protection (POL + ORG) in relation to CONV promoted an increase in the productivity of Conilon coffee by 6.8 % (5.4 sc ha-1) and 11.6 % (10.4 sc ha-1) in the 2017/2018 and 2018/2019 harvests, respectively. The greater quantity of phosphate fertilizers (Q150) and the application of UP, in general, resulted in greater productivity of processed beans in coffee.