Impactos das doses e do parcelamento da fertilização na produtividade, lixiviação e ciclagem de nutrientes em plantações de eucalipto

Abstract

It is occurring, in Brazil, the expansion of planted forest area with species that belong to the Eucalyptus genus, one of the reasons is the high biomass productivity resulting from the research and the operational improvements that have been implemented during the last decades. In several field experiments, has been observed an increase of eucalypts growth by using a higher amount of fertilizers. But excessive or inappropriate application of fertilizers may generate the fertilizer waste and nutrients leaching that may contaminate soil and watertable. The objective of this study was to evaluate the effect of fertilization doses in the biomass production and nutrient cycling from the eucalypt plantation, as well as evaluating the N and K leaching in the soil after the application of split and single dose of N and K fertilization. The experiment was set up in the Anhembi city (State of São Paulo), and it was constituted by five treatments with doses of fertilizers and N and K in split application (4 times) and also a treatment with a single dose of N and K application, 3 months after planting. It was evaluated the wood volume, root and shoot biomass, concentrations and stocks of nutrients in eucalypts biomass (mineralomass), the efficiency of nutrient use, the nutrient transference from the canopy to the soil through litter production (leaf-fall), internal nutrients cycling (biochemical cycle), the water flow and leaching of N and K in the soil at the depths of 20 and 90 cm. The eucalypts responded positively to the increased fertilization doses, especially in the first year, with higher productivity (height, DBH and biomass). Treatment with the highest dose for 24 months produced 105 tons ha -1 of biomass, 48% higher than the treatment without fertilization, with only 71 tons ha -1 . However the effect of higher doses was more evident at an early stage of tree growth, up to 12 months of age. However, the difference decrease over time, and at 24 months there were not significant differences among the treatments with fertilization application. Fertilization also resulted in higher nutrients accumulation (mineralomass) in all tree components (leaves, branches, wood, bark and roots) and increased nutrient transfer to the soil through deposition of leaf litter. Thus, the eucalypts applied the highest addition of fertilization dose returned to the soil through litter, about 50 kg ha -1 yr -1 of N, 20 kg ha -1 yr -1 of K and 80 kg ha -1 yr -1 of Ca, while the treatment without fertilization transferred to the soil only 25 kg ha -1 yr -1 of N, 6.5 kg ha -1 yr -1 of K and 47 kg ha -1 yr -1 of Ca during 12 months (between 12 to 24 months after planting). It was observed more efficient use of nutrients from the eucalypts with lower nutrients availability. Also, there were no significant differences in the growth of eucalypts from the treatments with split N and K application and single N and K application. However, there was a higher leaching of K and N, 90 cm deep, in the single application treatment.

Doses of N, P and K in the cultivation of eucalyptus in soil originally under Cerrado vegetation

“…According to Silva (2011), greater eucalyptus yield with increased fertilizer doses has been demonstrated in several experiments. These results changed fertilization management in commercial plantations, which in the past did not apply fertilizers, or applied small amounts, while currently plantations receive high doses of fertilizers.…”

“…Alves (2011) stresses that specific fertilization recommendations should be made for each genetic material due to the marked and differentiated nutrient requirements among them. According to Silva (2011), the recommendation in the literature needs to be reevaluated, especially due to the use of more productive and likely more demanding genetic materials than those used to produce the original recommendation.…”

Potassium Fertilization of Eucalyptus in an Entisol in Low-Elevation Cerrado

“…The addition of nutrients to the soil by leaf deposition in the period from 30 to 66 months was estimated by multiplying the senescent leaf deposition by the nutrient content in the leaf. At 66 months after planting, four trees in the useful area of each plot of one block were cut, where one tree was representative of the small-diameter class, two represented the intermediate-diameter class, and one was representative of the large-diameter class, according to the method described by Silva (2011). Samples of all components of the trees (leaves, branches, and trunk) were collected manually for the determination of the moisture in the laboratory and the subsequent quantification of the dry biomass.…”

“…Ideally, Eucalyptus crops are fertilized before canopy closure, and after this period, there is practically no response from the crop to fertilization, due to the beginning of Rev Bras Cienc Solo 2018;42:e0180085 the biogeochemical cycle. This cycle is responsible for the maintenance and supply of nutrients to the plants through the deposition of leaves, branches, and other parts of the plant on the soil, which form the litter layer, providing nutrients through decomposition (Laclau et al, 2003;Silva, 2011;Benatti, 2013).…”

“…The understanding of nutrient removal from the soil by its extraction and, consequently, the export of nutrients upon wood harvesting is of great importance to the understanding of the inputs and outputs of the nutrients during the crop cycle (nutrient balance). To maintain and improve the soil chemical properties in Eucalyptus plantations, the nutrient balance should be adequately monitored, mainly by fertilization and the correct management of crop residues (Silva, 2011).…”