The Role of Cropping System Complexity in Soil Organic Matter Formation and Nutrient Availability

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Commodities

• Fruits: berries (blueberries)
• Vegetables: cabbages, carrots, cucurbits, greens (leafy), greens (lettuces), okra, radishes (culinary), tomatoes
• Additional Plants: ornamentals

Practices

• Crop Production: conservation tillage, cover crops, cropping systems, crop rotation, high tunnels or hoop houses, no-till, nutrient cycling, organic fertilizers
• Production Systems: integrated crop and livestock systems, organic agriculture
• Soil Management: composting, green manures, organic matter, soil analysis, soil chemistry, soil quality/health

Nitrogen (N) is often the limiting nutrient for plant growth in agricultural cropping systems. However, inorganic sources of N are prone to losses through leaching or volatilization, which has contributed to negative environmental effects such as greenhouse gas emissions and nutrient pollution. Identifying stable sources of bioavailable N will be critical to support sustainable intensification of cropping systems while also minimizing environmental impact. Recent discoveries have led to the understanding that plants can take up substantial amounts of N mobilized from generally slow-to-decompose forms of soil organic matter, including mineral-associated organic matter. The goal of this study is to examine the role that agricultural management plays in soil organic matter formation and soil organic N bioavailability. In this study, we will use high-dimensional, complex site-descriptive data from regional small-scale organic vegetables farms to provide information on the relationships between management practices and soil organic N pools and bioavailability. This study will provide an opportunity to form relationships with small-scale growers in the region and develop a survey approach to capture the complexity of agricultural management practices. We will also evaluate the role of organic input (compost, manure, etc.) diversity on soil organic matter formation and N bioavailability in an organic system. We will establish a replicated field study comparing different organic input sources and combinations. Ultimately, information from this study could inform management strategies to build reservoirs of soil organic N for sustainable N management in cropping systems.

1. Provide an extension opportunity for small-scale farmers in Virginia to evaluate the influence of their own complex organic cropping systems on SOM formation.
   1. Develop a surveying approach to capture information on commonly applied organic inputs, crop rotations, and other management practices such as animal integration or tillage in small-scale organic vegetable systems.
   2. Provide information to participating farmers on how their management practices relate to on-farm variation in SOM amount and N bioavailability.
   3. Use high-dimensional site-descriptive data to provide a starting point for interpretation of relationships between complex management systems and SOM pools.
   4. Produce a factsheet reporting emerging patterns between management practices and SOM pool dynamics.
2. Evaluate the role of organic input complexity on SOM formation and N bioavailability in an organic system. For this objective, I hypothesize that overall higher complexity will promote the formation of SOM, and specifically MAOM, due to the potential for more diverse pathways of MAOM formation (Kleber et al., 2015).
   1. Establish a replicated field study that isolates effects on organic input complexity on formation of SOM pools (total, particulate, and mineral-associated) and organic N bioavailability.
   2. Produce a primary research conference presentation and publication to disseminate findings.