Fontes de silício e corretivos na agricultura: efeitos sobre os atributos químicos e físicos do solo e na produtividade do trigo, milho e cana de-açúcar.

Abstract

The growing global concern over increasing food demand has led to the expansion of new agricultural areas. However, environmental issues—such as the reuse and recycling of waste discarded by industries—have prompted reflection on how to boost agricultural productivity while ensuring both economic gain and environmental sustainability. In this context, new technologies have been refined and implemented in the agricultural sector with the goal of reducing production costs and increasing crop yields. One notable example is precision agriculture, which uses tools such as electrical conductivity measurements combined with chemical and physical soil analyses. These techniques contribute to sustainable and balanced management practices, preventing drift and leaching of many agricultural inputs, as well as ensuring the correct application of fertilizers. For this reason, the first chapter of the thesis evaluated whether there was any interference in the chemical and physical properties of the soil in relation to electrical conductivity and the productivity of wheat and corn crops after the application of limestone and silicate. This phase of the study was carried out on a commercial agricultural property located in the municipality of Céu Azul, in the state of Paraná, Brazil. After soil collection and chemical analysis, application rates were established at 0, 300, and 800 kg·ha⁻¹ for the control, silicate, and limestone treatments, respectively. To measure soil electrical conductivity, an EM38-MK2 conductivity meter was used. Data cleaning, interpolation, and correlation analyses were conducted using the AgDataBox platform. Results showed that only the nutrient calcium presented a significant difference between the silicate and control treatments, based on the chemical sampling conducted in 2022. Regarding the correlation matrix, autocorrelation among chemical elements was observed; however, there was no correlation between electrical conductivity and magnesium in the 2024 crop season. Additionally, autocorrelation was found between soil compaction resistance and different depths, soil texture, and yield levels. A significant difference was also observed in soil compaction resistance between the control and silicate treatments. It was concluded that both positive and negative correlations, as well as autocorrelations, existed between the parameters analyzed and soil electrical conductivity. In the second chapter of the thesis, the objective was to analyze the use of different silicon sources in sugarcane production in the state of Louisiana, United States of America. The experiment was conducted at the Louisiana State University Agricultural Research Station. Fertilization treatments consisted of the application of 0 kg·ha⁻¹ for the control, 2471 kg·ha⁻¹ for the limestone treatment, 2471 kg·ha⁻¹ for the sugarcane bagasse ash treatment, and 1235.5 and 2471 kg·ha⁻¹ for the silicate slag treatments. The experimental design used was a randomized block design, with plots consisting of three rows measuring 30.48 meters in length, using the sugarcane cultivar L01-299. Soil and leaf samples were collected 30 days after fertilization and again at harvest. In the laboratory, soil electrical conductivity analyses and colorimetric determinations were performed to quantify silicon in both soil and plant tissue. It was observed that soil electrical conductivity values were higher 30 days after fertilizer application compared to those measured at harvest time. The soil silicon analyses showed similar results between the two sampling periods, with no significant differences among the fertilization treatments. The treatments evaluated 30 days after fertilization exhibited higher silicon concentrations in the plants compared to those measured at harvest. In conclusion, soil silicon levels remained relatively consistent across the different sampling times; however, the highest concentration, 182.28 mg·kg⁻¹, ix was obtained 30 days after fertilization in the treatment with 2471 kg·ha⁻¹ of silicate. Regarding silicon content in the plant, the highest level (2.50 mg·kg⁻¹) was observed in the limestone treatment 30 days after application, while a lower value (0.86 mg·kg⁻¹) was recorded for the same treatment at harvest. Overall, it can be concluded that sustainable management practices combined with the use of technological tools lead to increased productivity and profitability for producers, while also ensuring the preservation of a clean and balanced environment for future generations.