Rice-pasture agroecosystem intensification affects energy use efficiency

Abstract

Sustainable rice production systems are key to food security. Diversified farming systems are essential for ecological intensification and environmental enhancement. Energy use efficiency is one of the main sustainability indicators in agroecosystems. Thus, an assessment of consumption and efficiency of energy in contrasting cropping systems can discriminate their management practices and components sustainability. The goal of this study was to evaluate the energy performance through energy return on investment (EROI) in four rice-based rotation systems that belong to a long-term experiment located in the Temperate Grassland Terrestrial Ecoregion, at the Atlantic side of South America. Rotations analyzed consisted in: a) continuous rice (Rc); b) rice-soybean (R−S); c) rice-pasture for 1.5 years (R−PS); and, d) rice-pasture for 3.5 years (R−PL). The EROI estimations considered all the inputs and outputs of energy from cradle to farm gate. The greatest EROI was observed in R–S (7.2 MJMJ−1) and the lowest energy consumption in R−PL (10,607 MJ(hayr)−1). The R−PL’s EROI (6.7 MJMJ−1) was 6.5% and 8% higher than Rc and R−PS EROI, respectively. Rotations without pastures produced 79% more energy compared with rotations including pastures. However, energy inputs of rice-pasture rotations were 40% lower than either R−S or Rc. The EROI (without animal production) of R−PS, R–S and Rc was 25%, 28% and 43% lower than the EROI of R−PL (10 MJMJ−1), respectively. For the analyzed South American ecoregion, EROI assessments of four business as usual rice production systems allowed to discriminate and hierarchize their sustainability and diversity.