System diversification and grazing management as resilience-enhancing agricultural practices: The case of crop-livestock integration

Abstract

Managing for resilience in agriculture will be required to overcome future challenges such as growing food demand, climatic uncertainty, scarce raw materials and economic instability. Identifying resilience-enhancing practices is therefore fundamental for developing sustainable agroecosystems. We aimed to assess the resilience of two agricultural systems with different levels of diversification in southern Brazil: a specialized soybean (Glycine max) system and an integrated soybean-beef cattle system. We assessed the robustness and the adaptive capacity of these systems when facing climate hazards and price volatility. The study was based on a long-term trial that has been carried out since 2001, composed of an annual rotation of no-till soybean production during the summer and grazing of mixed black oat (Avena strigosa) and Italian ryegrass (Lolium multiflorum) pasture in the winter. Treatments consisted of four grazing intensities in the integrated crop-livestock system (ICLS), defined by sward heights: 10, 20, 30 and 40 cm plus an ungrazed control representing the specialized cropping system (CS). The experiment was carried out using a randomized complete block design with three replicates. We analysed system results over five years using two methods: i) a downside risk analysis to estimate the expected losses of yield and gross value added; and ii) the Ecological Network Analysis, which was applied to each treatment and year, for the assessment of the resilience of nitrogen (N-Ɍflow) and phosphorus (P-Ɍflow) flows. Both methods showed that co-located crop-livestock production in an ICLS was more resilient than the specialized soybean system and had improved nutrient cycling and resource-use efficiency. The effects of grazing management on system resilience depended on the output: beef yields were more stable under lower grazing intensities, but the risk of falling below a target economic threshold was inversely proportional to grazing intensity and null when the highest grazing intensity was adopted. The ecological network analysis did not reveal differences in resilience of nutrient flows among grazing management treatments. Our study suggests that Ɍflow (N or P) is a useful proxy for assessing the robustness and adaptability of agroecosystems. Our comprehensive resilience analysis of nutrient and economic flows provides evidence that system diversification through the integration of grazing animals into specialized cropping systems is a good strategy towards the sustainable intensification of agriculture. It would be relevant, however, to consider further studies comparing more complex system configurations and levels of diversification.