Remote Sensing and Sustainability Analysis of Sugarcane within the Everglades Agricultural Area

Abstract

I evaluated the relationship of nitrogen runoff and the practice of burning sugarcane in Everglades Agricultural Area (EAA) in southern Florida. The soil in the EAA is composed of nitrogen rich peat, which is a few inches to many feet deep over a limestone base. Over time the peat begins to break down due to oxidation, drying, temperature (Qualls & Richardson, 2008), and burning. Prior to harvesting the sugarcane, the fields are burned to remove excess green vegetation, leaving behind sugarcane burn residue (BR). Sugarcane burning results in exposed soil, which allows for precipitation to erode the BR and decaying peat (Bordonal et al., 2018). Nutrient loss in BR is also statistically more sensitive to precipitation (Udeigwe et al., 2009). The nutrient loss, due to runoff and peat decomposition, results in a net loss of nitrogen in the sugarcane fields and nutrification in downgradient wetlands (SFWMD, 2020). A research gap exists for assessing the correlation of sugarcane burning and nitrogen nutrification within the EAA and downstream wetlands. To address this knowledge gap, I tested the hypotheses that: 1a) there is a direct correlation between the sugarcane field burning within the EAA and increased nitrogen, with precipitation as a driving transport mechanism, within the downgradient water; 1b) regional differences exist between the scale of the burning each year and soil nutrient loss as measured through water quality observations; 2a) substantial environmental benefits can be realized by mitigating N impacts by altering sugarcane farming practices to reduce burning; and 2b) some of the alternative practices to burning are cost-effective. To determine the relationship between the traditional sugarcane practice of pre-harvest burning and nitrogen levels in nearby wetlands, I first defined a study area within EAA that was hydraulically confined by major canals. I obtained precipitation and nitrogen levels from multiple Water Quality Stations (WQS) and satellite imagery for remote sensing analyses, specifically utilizing the normalized difference vegetation index (NDVI) to evaluate healthy sugarcane versus burned ground. I evaluated the data to determine statistical outlying data points, with nitrogen representing soil loss, precipitation as the erosional driving mechanism, and NDVI as the evaluation of the current ground cover. I was able to statistically correlate burned ground to the NDVI in the study area. The NDVI, precipitation, and nitrogen outlying values were indirectly correlated by graphing them as a twenty-year time-series and observing the seasonal trends. The results of the time-series analysis indicated an indirect correlation between the sugarcane burning and nitrogen levels and the results varied regionally. To determine if sustainable change be made to the commercial sugarcane industry, I devised three cost-benefit analyses (CBA) of alternatives: replacing sugarcane harvesters with a more efficient model; processing the green trash and bagasse into biochar for resale; and planting cover crop, Sunn Hemp, during the fallow year to aid in soil stabilization, nutrient loss prevention, and pest control. The results of the CBA indicated all three are viable options. Options 2 and 3 indicated significant potential to improve the soil and as a result reduce the environmental impact due to soil loss. The conclusions of my research indicated multiple possible solutions to the environmental impact and soil loss to sugarcane farming while still remaining profitable, resulting in a prosperous sustainable symbiotic future for the sugarcane industry and the environment.