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Published on: July 4, 2014
Using remote sensing to identify liquid manure applications in eastern North Carolina
Kelly Shea1, Danica Schaffer-Smith2, Rebecca L Muenich3
1School of Geographical Sciences and Urban Planning, Arizona State University, Tempe, AZ, USA; School of Sustainable Engineering and the Built Environment, Arizona State University, Tempe, AZ, USA.
Nutrient pollution from farm fertilizers and manure is a global concern. Excess nitrogen and phosphorous has been linked to algal blooms and a host of other water quality issues. In the U.S., most animal production occurs in concentrated animal feeding operations (CAFOs) housing a significant number of animals in a confined space. CAFOs tend to cluster in space and thus generate large quantities of manures within a small area. Liquid manure from CAFOs is often stored in open-air lagoons and then applied via irrigation to crops on nearby 'sprayfields'. The full scope and extent of CAFO impacts remain unclear because of the paucity of public information regarding animal numbers, barn and lagoon locations, and manure management practices. Where and when manure is applied on the landscape is key missing data that is needed to better understand and mitigate consequences of CAFO management practices. The aim of this study was to detect land applications of liquid manure using a remote sensing approach. We used random forest models incorporating C-Band synthetic-aperture radar, multispectral imagery, and other predictors to examine soil moisture conditions indicating probable liquid manure applications across known sprayfields in eastern North Carolina. Our models successfully distinguished saturated and unsaturated soils within corn, soybean, grassland, and 'other' crops, with 93-98% accuracy against validation for clear weather periods during the dormant, early, and late growing seasons. A Kruskal-Wallis test revealed that the mean soil saturation frequency was significantly higher on sprayfields than non-sprayfields of the same crop type (p < p 2.2e-16). We also found that manure applications were concentrated within ∼1 km from the point of generation. This is the first application of satellite-based radar for identifying the location and timing of manure applications over broad areas. Future work can build on these methods to further understand manure management at CAFOs, as well as to improve pollution source tracking and modeling.
Area of Science:
- Environmental Science
- Remote Sensing
- Agricultural Science
Background:
- Nutrient pollution from agricultural sources, particularly excess nitrogen and phosphorus from farm fertilizers and manure, poses a significant global environmental challenge.
- Concentrated animal feeding operations (CAFOs) in the U.S. generate substantial manure volumes in localized areas, often stored in lagoons and applied to nearby sprayfields.
- Limited public data on CAFO operations and manure application practices hinders a comprehensive understanding of their environmental impacts.
Purpose of the Study:
- To develop and apply a remote sensing methodology for detecting land application of liquid manure.
- To identify the spatial and temporal patterns of manure application on agricultural landscapes.
- To improve the tracking and modeling of pollution sources associated with CAFOs.
Main Methods:
- Utilized random forest models integrating C-Band synthetic-aperture radar and multispectral imagery.
- Analyzed soil moisture conditions to identify areas of probable liquid manure application.
- Validated models across diverse crop types (corn, soybean, grassland) in eastern North Carolina during different growing seasons.
Main Results:
- Remote sensing models achieved high accuracy (93-98%) in distinguishing saturated from unsaturated soils indicative of manure application.
- Significantly higher soil saturation frequencies were observed on sprayfields compared to non-sprayfields of the same crop type (p < 2.2e-16).
- Manure applications were found to be concentrated within approximately 1 km of the manure generation point.
Conclusions:
- This study presents the first successful application of satellite-based radar for broad-area identification of manure application timing and location.
- The developed remote sensing approach offers a valuable tool for monitoring CAFO management practices and mitigating associated pollution.
- Future research can leverage these methods to enhance pollution source tracking and environmental impact modeling related to agricultural operations.
