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| Author(s): |
Saulo Augusto Quassi de Castro
Total Authors: 1
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| Document type: | Doctoral Thesis |
| Press: | Piracicaba. |
| Institution: | Universidade de São Paulo (USP). Escola Superior de Agricultura Luiz de Queiroz (ESALA/BC) |
| Defense date: | 2022-07-29 |
| Examining board members: |
Paulo Cesar Ocheuze Trivelin;
Heitor Cantarella;
Carlos Alexandre Costa Crusciol
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| Advisor: | Paulo Cesar Ocheuze Trivelin |
| Abstract | |
Sugarcane is one of the main agricultural crops produced in Brazil and is important worldwide not only because it produces sucrose, but especially because of the increased demand for renewable fuels, e.g., ethanol, to reduce the greenhouse gases emission. Nitrogen is the second most demanded mineral essential element by sugarcane, applied annually to the soil to obtain a long-lived and productive sugarcane field, however, much of it remains in the soil and can be lost to the environment. In foliar nitrogen fertilization, the N-fertilizer recovery by the plant is greater, when compared to soil nitrogen fertilization, and allows for synchrony between the sugarcane plant requirements and the N-fertilizer application. In this context, it can be inferred that foliar nitrogen fertilization in addition to the soil nutrient application will provide a balance between biomass production and the environment, bringing benefits to sustainability in sugarcane agrosystems with financial gains. To validate this hypothesis, experiments were conducted under controlled conditions and in the field. Firstly, the objective was to evaluate the sugarcane leaves anatomy so that contrasting varieties could be used in experiments aiming at foliar fertilization with urea. Fourteen sugarcane varieties were selected, the most planted in southeastern Brazil, and grouped according to leaf anatomical characteristics and related to leaf absorption pathways. Four contrasting varieties in terms of anatomical variables were selected and used in an experiment carried out in greenhouse conditions to evaluate the N-fertilizer recovery and redistribution applied to the leaves (15N-urea) as a function of the nitrogen concentration in the solution (8, 16, 24 and 36 % 15N-urea). Sugarcane varieties differed in the absorption rate of 15N-urea. At 5 days after foliar nitrogen fertilization there was, a maximum of nitrogen absorption, reaching up to 78 % of 15N-urea recovery. Up to 20 days there was a 15N-urea redistribution; stalk and not- expanded leaves were the nitrogen sinks. One of the sugarcane varieties used in the greenhouse experiment was selected and used in the field experiments to validate this nitrogen fertilization management. Two field experiments were carried out, for three years, to evaluate the sugarcane biomass production and juice quality when foliar nitrogen fertilization was carried out in the maximum plant growth period as a complement to soil nitrogen fertilization. Fifteen treatments were installed, i.e., 0 + 0, 40 + 0, 60 + 0, 80 + 0, 120 + 0, 160 + 0, 0 + 12, 0 + 24, 0 + 36, 40 + 12, 40 + 24, 40 + 36, 60 + 12, 60 + 24, and 60 + 36 kg ha-1 N applied, respectively, to soil and to the leaves. In the sum of the three years, both sites were responsive to nitrogen fertilization and demonstrated that it is possible to reduce the soil nitrogen fertilization rate without causing damage to sugarcane biomass production and juice quality. In the 2nd year of the experiments, 15N-urea was applied to the leaves and the N-fertilizer recovery by the plant was, on average, 53 %, differing between sites. It is concluded that the use of foliar nitrogen fertilization is an important tool for the adjustment of nitrogen fertilizer management in sugarcane in order to obtain a long-lived, productive, and environment-friendly sugarcane field. (AU) | |
| FAPESP's process: | 17/25489-3 - Nitrogen (15N) use by sugarcane submitted to nitrogen fertilization with "leaf spray" (N-Urea) as a complement to the soil nutrient application |
| Grantee: | Saulo Augusto Quassi de Castro |
| Support Opportunities: | Scholarships in Brazil - Doctorate |