Soil CH4 and N2O Emissions from Rice Paddy Fields in Southern Brazil as Affected by Crop Management Levels: a Three-Year Field Study

Carla Machado da Rosa,Gabriel Munhoz Pedroso,Madalena Boeni,Daiane Carvalho dos Santos,Estefânia Silva Camargo,Cecília Estima Sacramento dos Reis,Cimélio Bayer,Tiago Zschornack

doi:10.1590/18069657rbcs20170306

Abstract

ABSTRACT Rice yield increases in response to improvements in crop management, but the impact on greenhouse gas (GHG) emissions in the subtropical region of Southern Brazil remains unknown. A three-year field study was developed aiming to evaluate the impact that an increase in crop management levels (high and very high) has on soil methane (CH4) and nitrous oxide (N2O) emissions, as compared to the level (medium) currently adopted by farmers in Southern Brazil. Differences in crop management included seed and [...]

Highlights

Rice is one of the most important foods in the human diet and the second most frequently grown cereal in the world (Sosbai, 2014)
Methane fluxes occurred mainly during the rice season and ranged from -0.80 to 855.50 g ha-1 h-1, and their behavior at that time was similar for all crop management levels (Figure 2)
The gradual increase in CH4 emissions after flooding are consistent with anoxic conditions in flooded soil, once pH and Eh have leveled off and oxidized species such as NO3, Mn4+, and Fe3+ have been microbially reduced (Silva et al, 2011)

Summary

Introduction

Rice is one of the most important foods in the human diet and the second most frequently grown cereal in the world (Sosbai, 2014). The rice production system in RS, where the rice crop area exceeds 1.0 million hectares each year, requires a 0.05-0.20 m thick layer of water to be maintained on the soil throughout the crop cycle (IRGA, 2006; Sosbai, 2014) These conditions boost production of CH4 through anaerobic decomposition of soil organic matter or crop straw by methanogens (Le Mer and Roger, 2001). In addition to transferring CH4 from the soil to the atmosphere, rice plants supply substantial amounts of labile C to methanogens by accumulating likewise substantial amounts of photoassimilated C in their roots (Lu et al, 2000; Aulakh et al, 2001) In this situation, increasing inputs ( fertilizers) to a rice crop may boost CH4 emissions from the soil through the effect of increased exudation of organic compounds by the root system to raise yields (Das and Baruah, 2008)

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