Understanding management effects on soil organic matter and ecological function in forage-based agroecosystems.

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The world's soils, are increasingly being acknowledged for their potential contribution to the fight against climate change, nutrient pollution, and to provide other critical ecosystem services. Cropping systems that include forage and service crops (pasture, hay, cover crops) are known to increase carbon sequestration and provide numerous benefits to soil health and nutrient cycling. In particular, grazed agricultural grasslands show much potential for sequestering carbon by increasing belowground biomass; for example, some studies have indicated that net negative greenhouse gas emissions are possible for a predominantly grass-fed beef operation, when rotational grazing (where livestock are rotated frequently through paddocks, and allowing adequate rest periods) is employed. An improved understanding of how grazing management and pasture fertilization impact soil carbon sequestration is required in order to better contribute to climate change mitigation.   The objectives of this proposal are to determine the agro-ecological benefits provided by forage and service crops and to identify management practices that increase these benefits. In particular, I will focus on grazing management in beef production systems and how rotational grazing strategies and nitrogen fertility management can impact carbon sequestration. My research will examine the quality of the soil organic matter in order to better understand its ecological function (how stable it is, etc.). I will also quantify the soil health benefits provided by including perennial forage in a cropping system rotation in terms of the ability to lower fertility recommendations for a subsequent crop. These research questions will be accomplished through a combination of on-farm, controlled environment, and research station studies. My research program will provide data that will further scientific understanding on the mechanisms enhancing carbon sequestration in grazed ecosystems and make recommendations to enable improved soil carbon management in grazed soils. This research is expected to improve the environmental outcomes of the beef industry by identifying grazing management strategies that improve their productivity and ecological impacts (carbon sequestration) at the same time. This is important because the beef industry is frequently under scrutiny for being a major greenhouse gas contributor, but contributions to soil carbon sequestration during grazing are typically not considered. Finally, improvements in soil quality due to the use of forage-based cropping systems that promote soil organic matter and soil health are expected to have implications for the amount of nutrients that are needed to be applied as fertilizers. Practices that may reduce the amount of nutrients, particularly P, required in agriculture are needed; this is a current cross-sector priority, and critical for the health of the Lake Erie watershed.