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

Commodities

Practices

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.