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Leaching of nitrate in soil columns affected by texture, nitrogen doses and added water depth

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Sérgio Esteves de Freitas
Total Authors: 1
Document type: Master's Dissertation
Press: Botucatu. 2021-03-31.
Institution: Universidade Estadual Paulista (Unesp). Faculdade de Ciências Agronômicas. Botucatu
Defense date:
Advisor: Ciro Antonio Rosolem; Eduardo Mariano

Losses by leaching of nitrate (NO3 - ) can result in contamination of groundwater and reduce the efficiency of use of the nutrient by the cultures. Soils with a sandy texture, rich in organic N, intense rainfall and high doses of nitrogen fertilizer are reported as the main factors that favor nitrate losses by leaching. The aim of the study was evaluate the effect of water percolation, available nitrogen in the soil profile and application of fertilizer in the nitrate leaching depending on the texture of the soil. Three experiments were carried out in a greenhouse, in the first treatment consisted of five soil textures (28, 176, 321, 467 and 626 g kg-1 of clay) and four water levels (control, 675, 1006 and 1345 mm). For the second experiment, the treatments were three soil textures (28, 321 and 626 g kg-1 of clay) and three levels of N in the soil (control and cultivation of corn and soybeans). In the last experiment, the treatments consisted of two soil textures (28 and 626 g kg-1 of clay) and four doses of N (0, 80, 160 and 240 kg-1 ha) applied in the form of ammonium sulfate [15 (NH4)2SO4] labeled with 10.3% 15N atoms. This study provides an important information regarding NO3 - leaching, taking into account some factors mentioned in the literature. The addition of water, the enrichment of the soil profile with the growth of soybeans and the use of high doses of N can increase losses by leaching of NO3 - . In general, clay soils showed higher N leaching, especially in NO3 - form. However, in this case, there is evidence that a large part of the leached N is from the soil and not from to the fertilizer, unlike the sandy one, which has a low content of native N. In regions with historical averages of high rainfall, soybean growth may benefit the leaching of NO3 - due to its high lability benefiting the accumulation of nitrate in the soil profile. Losses by leaching of NH4 + are observed in small amounts, however considering high doses in sandy soils the losses can be high. Finally, rational doses of N (for example, those that aim to replace the amount of N extracted or exported by the crop) may benefit the decrease in NO3 - losses in agricultural systems. (AU)

FAPESP's process: 18/04739-4 - Leaching of nitrate in soil columns affected by texture, nitrogen doses and added water depth
Grantee:Sérgio Esteves de Freitas
Support Opportunities: Scholarships in Brazil - Master