Examining Carbon-Farming Practices to Address Soil Sustainability in the Everglades Agricultural Area, South Florida

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Commodities

• Agronomic: rice, sugarcane

Practices

• Crop Production: cover crops, fallow
• Soil Management: soil physics, soil quality/health, carbon sequestration, mitigation

The Everglades Agricultural Area (EAA) located in South Florida is approximately 283,000 ha in size, comprising of highly organic soils (Histosols). However, this fertile “muck” soil has been experiencing soil loss via microbial organic matter (OM) oxidation, locally referred to as “soil subsidence” which is known to decrease soil health and agricultural sustainability within the region. Increasing concern about the long-term sustainability of agricultural production within the EAA has emphasized the need for developing C-farming practices including (i) crop rotation (flooded rice with sugarcane), (ii) flooded-fallow instead of fallow fields, and (iii) growing cover crops that can enhance C input and reduce rate of microbial OM oxidation particularly during the hot dry periods. However, long-term quantitative studies evaluating the effects of these C-farming practices on soil subsidence are lacking. Therefore, the overall objective of this study is to identify C-farming practices among these existing farming practices that can address soil subsidence within EAA. The specific objective of this study is to investigate the impact of these existing farming practices on (i) C input, (ii) soil enzymatic activity associated with mineralizing soil C to CO₂, and (iii) active carbon, which is a portion of OM susceptible to be mineralized to CO₂ by soil enzymes. Knowledge of C input, soil enzymatic activities and active carbon will help growers, and land managers in decision-making when selecting C-farming practices that could potentially mitigate soil subsidence, thus, improving and sustaining soil for food production while lowering C losses to the atmosphere within EAA.

The overarching objective of this study is to test a subset of a four-year long PhD project, specifically focusing on the impact of currently applied BMPs on C input, and changes in (i) soil C stock, (ii) enzymatic activities controlling soil C stock due to their role in oxidizing soil C to CO₂, (iii) soil environmental factors influencing enzymatic activities, and (iv) active carbon, which is a portion of OM susceptible to be oxidized by microbial activity in Histosols, the purpose being to identify C-farming among existing BMPs that has potential to mitigate soil subsidence. We hypothesize that the proposed C-farming practices will increase soil C pool via atmospheric CO₂ sequestration and reduce soil loss via reducing enzymatic activities playing role in OM oxidation. To test this hypothesis, three separate field studies will be conducted on commercial farms within the EAA in collaboration with our local stakeholders (Florida Crystals, Sugar Cane Growers Co-Operative of Florida, Roth Farms, Veg Pro International, and Roth Farms).

Study 1 (Crop rotation [sugarcane and flooded rice])

The objective of this study is to quantify the above and below-ground biomass C input and evaluate changes in soil C stock, active carbon, microbial activity measured by extracellular enzymatic activities, and soil environmental factors under flooded rice as summer crop rotation compared to sugarcane farming practice.

Study 2 (Flooded- fallow versus fallow)

The objective of this study is to determine the effect of flooded fallow on soil C stock, active carbon, microbial activity measured by extracellular enzymatic activities, and soil environmental factors versus fallow fields within the EAA.

Study 3 (growing cover crops)

The objective of this study is to quantify the above and below-ground biomass C input and assess changes in soil C stock, active carbon, microbial activity measured by extracellular enzymatic activities, and soil environmental factors under different cover crops, the purpose being to determine the feasibility of growing cover crops during fallow period and identify suitable varieties that can be adopted by the growers during summer fallow period.