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Mineralizable nitrogen and maize responsiviness in crop rotation systems in Cerrado

Grant number: 19/00978-7
Support type:Scholarships in Brazil - Doctorate
Effective date (Start): September 01, 2019
Effective date (End): February 28, 2022
Field of knowledge:Agronomical Sciences - Agronomy - Soil Science
Principal Investigator:Rafael Otto
Grantee:Raíssa de Araujo Dantas
Home Institution: Escola Superior de Agricultura Luiz de Queiroz (ESALQ). Universidade de São Paulo (USP). Piracicaba , SP, Brazil


Nitrogen (N) is the nutrient required in high amounts by crops and is the widely applied worldwide. The estimate of soil's N potential of mineralization is importante for better the eficciency of nitrogen fertilization, regarding that the soil is the principal source of the nutrient for plants. However, include the soil's mineralizable N in methods of fertilizer recommendation is not yet used because the difficult to quantify. The Illinois Soil Nitrogen Test (ISNT), a method to estimate the mineralizable N by the alcaline extraction with NaOH, highlights as a promisse method. Posterior studies have evidenced that the method extracts a fixed ammount of organic N and, therefore, do not represent the labile fraction.The hipothesis of this study is that the extraction with NaOH used in ISNT method upperestimates the soil's N labile fraction. The objective is to evaluate the mineralizable N in summer maize rotation with cover crops (grasses, legumes and cruciferous), using chemical and biological methods, with emphasis on variation of NaOH's concentration in ISNT method. The evaluation will include: shoot dry matter, productivity and accumulation of N in maize, chemical methods (ISNT with 0,25, 0,5, 1,0 and 2,0 mol L-1 NaOH and permanganate oxidizible C), biological (aerobic incubation and ²-glucosidase and celulase enzymes) and N fertilizer recovery by maize (15N isotope tecnicque). The inovation of this propose is the partnership with Embrapa Cerrados, that has na long-term experiment with summer maize rotation with ten species (grasses, legumes and cruciferous), with and without N fertilizer. Preliminar results indicates that the difference in responsiveness to N by corn depending on rotation with cover crops. The evaluations in the experiment will be the indices to estimate N mineralizable on soil that can correlate with the maize response to N in field conditions. The new topic aborded in this study is the pursuit to a practical method toestimate the soil's N mineralizable that can be used in the future in nitrogen fertilization recommendation to maize. (AU)