Daily and seasonal patterns of CO2 fluxes and evapotranspiration in maize-grass intercropping

Cássia B Machado,Antonio C D Antonino,Rodolfo M S Souza,Eduardo S De Souza,José R De S Lima,Edevaldo M Alves

doi:10.1590/1807-1929/agriambi.v20n9p777-782

Abstract

ABSTRACT Studies that investigate the relationships between CO2 fluxes and evapotranspiration (ET) are important for predicting how agricultural ecosystems will respond to climate changes. However, none was made on the maize-grass intercropping system in Brazil. The aim of this study was to determine the ET and CO2 fluxes in a signal grass pasture intercropped with maize, in São João, Pernambuco, Brazil, in a drought year. Furthermore, the soil water storage (SWS) and leaf area index (LAI) were determined. The latent heat flux was the main consumer of the available energy and the daily and seasonal ET and CO2 variations were mainly controlled by rainfall, through the changes in soil water content and consequently in SWS. The agroecosystem acted as an atmospheric carbon source, during drier periods and lower LAI, and as an atmospheric carbon sink, during wetter periods and higher LAI values. In a dry year, the intercropping sequestered 2.9 t C ha-1, which was equivalent to 8.0 kg C ha-1 d-1. This study showed strong seasonal fluctuations in maize-grass intercropping CO2 fluxes, due to seasonality of rainfall, and that this agroecosystem is vulnerable to low SWS, with significant reduction in CO2 uptake during these periods.

Highlights

Long-term flux measurements of different crop species are necessary to improve our understanding of management and climate effects on carbon flux variability as well as cropland potential in terrestrial carbon sequestration (Béziat et al, 2009)
The intercropping sequestered 2.9 t C ha-1, which was equivalent to 8.0 kg C ha-1 d‐1
The area of study was in São João, Pernambuco, Brazil (8o 52’ S; 36o 22’ W; 705 m).The climate is hot and humid, with average annual rainfall of 782 mm, and the wettest trimester consists of the months of May, June and July and the soil is classified as Regolithic Neosol (Gondim et al, 2015)

Summary

Introduction

Long-term flux measurements of different crop species are necessary to improve our understanding of management and climate effects on carbon flux variability as well as cropland potential in terrestrial carbon sequestration (Béziat et al, 2009). In Brazil, these studies focus mainly on rain forest and grass (Randow et al, 2004; Meirelles et al, 2011) and none measured these fluxes in maize-grass intercropping system using the eddy covariance method in semiarid lands of Brazil.

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Results