RESUMO
New research frameworks that simultaneously address production and environmental goals are required to identify promising sustainable intensification options in high-yielding cereal systems. Here we estimated potential changes in environmental footprint associated with crop management practices aimed at breaking the yield ceiling for rice production in Uruguay. Results from a regional survey were combined with field experiments to integrate impacts on productivity and sustainability at two different intensification levels (average-yielding and high-yielding). Survey results indicate that high-yielding farmers produced 14% more grain compare to the regional average (7900 kg ha-1), with 25% to 99% lower agrochemical contamination risk and similar nitrogen use efficiency and carbon footprint. In on-farm trials, the alternative management practices increased yield beyond that of high-yielding farmers by up to 7% in small plots (8 site-years) and 15% in field-scale comparisons (6 site-years), yet an ex post assessment of environmental indicators shows significant decline of resource use efficiencies and increased carbon footprint. Thus, yield gains were not able to compensate for increased environmental footprint, highlighting the challenge of advancing the dual goals of SI in production systems nearing the yield ceiling. This study provides a simple but powerful framework for advancing SI in mainstream cereal production systems based on cost-effective modifications to existing agronomic experiments.
RESUMO
The environmental impact of rice agriculture is poorly studied in developing countries, mainly due to limitations of the analytical capacity. Here, we report the development of a clomazone enzyme-linked immunosorbent assay as a fast and cost-effective tool to monitor the dissipation of this herbicide along the harvest. Antibodies were prepared using different strategies of hapten conjugation, and the best hapten/antibody pair was selected. It proved to be a reliable tool to measure the herbicide in the 2.0-20 ng/mL range in field samples, with excellent correlation with high-performance liquid chromatography results. The assay was used to study the dissipation of the herbicide in the floodwater of experimental rice paddies in Uruguay. Large differences in the residual amounts of herbicide were observed depending on the flooding practices. Because of its robustness and simplicity, the assay may be useful to delineate and monitor management practices that can contribute to minimizing the release of the herbicide in the environment.