Rev. Bras. Ciênc. Solo.2020;44:e0190123.

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Nitrous oxide emissions from a tropical Oxisol under monocultures and an integrated system in the Southern Amazon – Brazil

Alexandre Ferreira do Nascimento , Renato de Aragão Ribeiro Rodrigues , Julia Graziela da Silveira , Jacqueline Jesus Nogueira da Silva , Vagner de Carvalho Daniel , Eduardo Reckers Segatto

24/abr/2020

DOI: 10.36783/18069657rbcs20190123

Resumo Gráfico

ABSTRACT

Although agriculture and livestock systems represent important sources of N₂O from the soil, they may also aid in emissions mitigation, mainly when integrated systems are taken into account, such as crop-livestock-forest, for food production. This work assessed the soil N₂O emissions from a tropical Oxisol under row-crop, livestock, forest monocultures, and an integrated crop-livestock-forest system in the Southern Amazon – Brazil. Soil N₂O emissions were measured using static chambers from November 2014 to October 2016 in four soil use systems [row-crop, livestock, forest, and integrated crop-livestock-forest (CLF)], and in a reference area under native forest fragment. For the whole period, the average of soil N₂O fluxes was 16.9, 12.2, and 15.4 µg N₂O-N m^-2 h^-1, to row-crop, livestock, and CLF systems, respectively, all with a similar average among them. The lowest fluxes were observed in the forest system and native forest fragment, with average fluxes of 4.0 and 6.3 µg N₂O-N m^-2 h^-1, respectively, both lower than the agricultural systems. The largest soil N₂O fluxes were observed throughout the rainy seasons in the row-crop, livestock, and CLF, mostly after N-fertilizer application to the soil surface or in the planted row. As a consequence, the cumulative emissions were greater in row-crop, livestock, and CLF systems, which in the averages of two cycles emitted respectively 1.40, 1.15, and 1.27 kg N₂O-N ha^-1 yr^-1, all different of the forest system and native forest fragment (0.33 and 0.52 kg N₂O-N ha^-1 yr^-1, respectively). Nitrogen fertilization and soil moisture influenced soil N₂O emissions of all systems assessed in the Southern Amazon. The N₂O emissions took place after both factors were met, corroborating the hole-in-the-pipe model. Even with more soil use intensification, once in the same area there were three cultures in succession during a year and perennial trees, CLF did not lead to greater N₂O emissions from the soil than row-crop and livestock. Thus, CLF represents a good option for N₂O mitigation for the edaphic and climatic conditions of the Southern Amazon.