Assessing the Eco-Efficiency of Rice Production in Uruguay.

Much emphasis has been placed in recent years on the need for the sustainable intensification of agricultural systems (i.e. achieving increased yields with reduced environmental impacts). Despite growing interest by the global agricultural community, few integrated assessments have been carried out to test the hypothesis that it is possible to achieve these often conflicting goals through improved crop management practices, particularly across large spatial scales and involving multiple sustainability indicators. To address this hypothesis, we evaluated the eco-efficiency of rice production in Uruguay at a national scale over a 20 year period (1993-2013). Uruguay represents an ideal case study for sustainable intensification as both land under rice production and the distribution of cultivars planted remained relatively stable during this period, while total national rice production increased by approximately 30%. National rice production statistics and crop management data were used to evaluate yields, land use efficiency, energy use efficiency, net energy yield, N use efficiency, N loss, freshwater N contamination risk, C footprint, and agrochemical contamination risk based on a combination of models, experimental results, and values from the literature. Results indicate that average yields, energy efficiency, and net energy outputs continually increased during this period. The overall C footprint of rice production in the country remained relatively stable, hence on a yield-scaled basis the C footprint decreased over time. However, increased N input rates resulted in higher estimated N losses and the sporadic use of specific crop protection products, particularly insecticides and to a lesser extent fungicides, contributed to elevated agrochemical contamination risk in several years. Rice in Uruguay is typically rotated with pastures which may mitigate some of these environmental risks (e.g. despite increasing N application rates, they remain in the range of 60-80 kg N/ha which is relatively low compared to international standards). This analysis provides a case study for other areas and highlights the importance of quantifying the benefits as well as potential tradeoffs associated with agricultural intensification efforts.