Abstract
The objectives of this work were to evaluate the CO2 emission potential of an Oxisol under integrated crop-livestock and no-tillage systems in the Brasilian Savanna; and to analyze the impact of soil temperature and soil moisture as factors that regulate the seasonality and the emission of C-CO2 in these systems. Field-scale study was carried out at Fazenda Brejinho, in Pedro Afonso-TO, under Oxisol. The production systems studied were integrated crop-livestock and no-tillage under cropped with soybean and corn. The amount of carbon (C) released from the soil in the form of CO2 (C-CO2) was evaluated using cylindrical chambers installed in the field with a vial containing sodium hydroxide to collect CO2 released from the soil (soil emission) in an interval of 15 hours. Five evaluations were conducted over crops growing season, started in 01/26 through 06/16/2015. Data were tested to analysis of variance and the means were compared with Duncan test at 5%. The emission of C-CO2 differed between treatments in all evaluation periods. On average, the temperature ranged from 26.5 to 27.7 °C, the soil moisture ranged from 12.2 to 15.7% and the C-CO2 emission ranged from 87.4 to 119.9 mg m-2 h-1. Temperature, soil moisture and the production systems contributed to the emission and seasonality of carbon dioxide emissions. The integrated crop-livestock cropped with soybean/corn rotation was the system that had the lowest carbon dioxide emission.
Highlights
The Tocantins state is part of the considered last Brazilian agricultural frontier for grain production (Horvat et al, 2015)
Temperature, soil moisture and the production systems contributed to the emission and seasonality of carbon dioxide emissions
The C-CO2 emission patterns were similar for all agricultural systems evaluated, including the Savanna, where maximum emissions were observed in February and the minimum in July; which indicates a normal seasonality in C-CO2 emissions, according to the climatic characteristics of each region
Summary
The Tocantins state is part of the considered last Brazilian agricultural frontier for grain production (Horvat et al, 2015) This region belongs to the low altitude Savanna biome that is characterized by high temperatures (both during the day and the night), high rainfall within a period of five months followed by seven dry months (Bortolon et al, 2016). The soils of the Savanna contain low contents of organic material, are highly weathered, and are composed of phyllosilicates 1:1 and iron and aluminium oxides. They are considered fragile with a high probability of being found in a degraded state (Donagemma et al, 2016). One of the key agricultural practices to achieve this goal is the no-tillage system (NTS) (Bayer et al, 2006, 2016; Carvalho et al, 2009) with the insertion of pasture
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