Nitrogen availability in eucalyptus plantations as a function of forest residue management and fertilization after two crop rotations

Author(s)

Leticia Delarizza Silvestre

• Document type: Master's Dissertation
• Press: Piracicaba.
• Institution: Universidade de São Paulo (USP). Escola Superior de Agricultura Luiz de Queiroz (ESALA/BC)
• Defense date: 2023-09-20

Examining board members

José Leonardo de Moraes Gonçalves; Rodrigo Eiji Hakamada

• Advisor: José Leonardo de Moraes Gonçalves

Abstract

The nitrogen released by mineralization is essential for the development of eucalyptus, a genus highly used in the forest sector. Keeping forest residues under the soil increases the availability of this element to the plant, increasing wood productivity. The objective of this work is to understand the kinetics of N mineralization after the removal of forest residues and non-fertilization at the end of the second rotation of a Eucalyptus grandis plantation, and to compare it with that of native vegetation from the site and with a plantation of Pinus oocarpa. The study was conducted in a long-term experiment located in the municipality of Itatinga, state of São Paulo. Treatments consist of different intensities of forest residue management (permanence or removal of crown, bark and litter), omission of N, P, K, Ca and Mg. The assessments consist of in situ N mineralization, forest growth, soil chemical properties and plant nutritional assessment. With this information, it was possible to infer the relationship between the N mineralization rate and the potential response to nitrogen fertilization, wood productivity and production sustainability. The effect of nutrient omission on productivity reduced over the years, but the effect of maintenance or removal of residues remained over the years, where removal reduced productivity by 20% at the end of the second rotation. The lack of potassium influenced the productivity and reduced the accumulation of biomass by 69%. The compartment with the highest biomass accumulation was wood, the largest among the macronutrients was S with 75% and of the micronutrients was B with 71%, however due to the high metabolic activity, the leaves showed significant nutrient accumulation. Litter deposition showed seasonality, with 24% greater deposition in the rainy season. The treatment that kept residues stood out over the one that removed residues in the chemical properties of the soil, even with interference from the fire, the maintenance of residues showed better results. The effects of soil temperature variation directly affected the ammonification and nitrification rates, thus the microclimate strongly influenced the amount and form of nitrogen available in the soil. The Cerrado had the highest N-total rate (16.39 kg ha-1 month-1) in the rainy season. The interaction between treatment and time on mineralization rate was not statistically different. (AU)

• FAPESP's process: 20/13191-2 - Nitrogen availability in eucalyptus and pinus plantation and in native vegetation in function of the forest residue management and fertilizer application after two crop rotations
• Grantee: Leticia Delarizza Silvestre
• Support Opportunities: Scholarships in Brazil - Master