Nitrogen in deep soils of Cerrado biome: environmental factor or crop management setback?

Abstract

The growing demand for food, associated with lesser available agricultural lands, will lead to a production intensification in preexisting produces areas. In this context, it is expected that Cerrado biome continue to play a major role as food producer, especially crops as soybean and maize. Although, soybean is capable to supply its own need of nitrogen (N) - through Biological Nitrogen Fixation (BNF) -, maize is greatly dependent of N fertilization. Among the N forms, the nitrate (NO3-) represents one of the most important whereas for plants uptake or leaching. Therefore, we propose a study with the hypothesis that the N found in deep soils of Cerrado biome (until 8 m) are related to the complementary effect BNF, N fertilization and land-use change (soil organic matter mineralization). The objectives are to answer two main questions: which is the origin of this N? and, ii) is the soil mineralogy influencing soil deep C and N. For this end, we will select areas under different managements at Tanguro ranch (municipalities of Canarana and Querência in Mato Grosso state, Brazil). We will evaluate soil mineralogy and carbon (C) and N fractions (total, labile and microbial biomass) and isotopic composition of C (13C/12C) and N (15N/14N; and 15N on nitrate and ammonium). At the end of the study, we expect to contribute in the discussion of soil deep N, collaborating with a better understanding of the mechanisms regarding N leaching and or stabilization in soil; and providing subsidies for policy makers related to land changes and land management practices. (AU)