GEOSPATIAL LANDSCAPE ANALYSIS FOR LIVESTOCK MANURE MANAGEMENT IN WESTERN PENNSYLVANIA
Open Access
- Author:
- Saha, Gourab
- Graduate Program:
- Agricultural and Biological Engineering
- Degree:
- Master of Science
- Document Type:
- Master Thesis
- Date of Defense:
- July 11, 2018
- Committee Members:
- Cibin Raj, Thesis Advisor/Co-Advisor
Herschel Adams Elliott, Committee Member
Heather Elise Gall, Committee Member
James Samuel Shortle, Committee Member - Keywords:
- land suitability
SWAT model
GIS
manure management
nutrient loading
leaching index
P index - Abstract:
- Intensive agricultural activities in Southeastern Pennsylvania (PA) are a leading source of nutrient and sediment pollution to the Chesapeake Bay. The Chesapeake Bay water quality regulations issued by the United States Environmental Protection Agency through the development of a Total Maximum Daily Load (TMDL) in 2010 mandate watershed-wide reductions of nitrogen, phosphorus, and sediment loads from agriculture by approximately one quarter by 2025. The state is exploring options to maintain a vibrant agricultural economy while simultaneously meeting water quality regulatory targets. One option the state is exploring is the potential to develop new agricultural activities in Western PA outside the Chesapeake Bay watershed. The soils of Western PA have relatively low soil fertility and therefore have the potential to act as nutrient sinks that could accept manure generated by new animal agriculture in the region. However, detailed environmental impact assessments need to be conducted in order to understand the risks that the potential new animal agricultural activities would pose to the region. The goals of the study are to conduct a geospatial analysis and develop tools to explore the potential for sustainable manure management in Western PA. Objectives of the study are to (i) develop a land-suitability framework for identifying environmentally feasible areas for manure application; (ii) develop decision-making support tools to delineate the area required to accommodate the manure generated from a new livestock farm (i.e., “manureshed”); (iii) quantify the potential impacts of manure-based farming on water quality and evaluate the consistency of the developed land-suitability framework. A case study was conducted in Armstrong, Indiana, and Westmoreland Counties located in Western PA. For the first objective, a land-suitability framework was developed for the case study areas that could identify the land most suitable for manure application, such that the risks to water quality are minimized. The framework first identifies potential areas available for manure application by excluding forest, urban areas, and waterbodies. The potential areas include row croplands, forage lands, and currently unutilized non-forested lands. Second, the framework assigns suitability levels (highly suitable, moderately suitable, less suitable, and not suitable) on each potential land by using seven environmental vulnerability factors as criteria. The environmental vulnerability factors including floodplains, proximity to streams, shallow soils, karst geology, excessive slope, soil leaching potential, and runoff potential were considered for assigning suitable levels. Collectively, the three case study counties had 130,700 hectares that were identified as potential areas for new agricultural activities. Using the methodology, the land-suitability framework estimated that of the potential area, about 2% (2,524 ha) as highly suitable, 33% (43,020 ha) as moderately suitable, 44% (57,925 ha) as less suitable, and 21% (27,112 ha) as not-suitable areas in these three counties for manure-based agriculture. For further analysis, highly suitable and moderately suitable areas were defined as Suitable Areas and less suitable and not-suitable areas were defined as Risky Areas for manure management. The three counties combined had 46,293 ha (114,392 acres) of Suitable Areas for sustainable manure management. Excessive slope (> 8%) and proximity to streams (within 61m) were the dominant vulnerability factors in the study area. For the second objective, a “manureshed”, defined as an area of land surrounding a livestock operation (of the specified type, size, and location) that contains enough suitable acreage for crop utilization of nutrients from the generated manure, was conceptualized for the appropriate manure management for a livestock farm. Two manureshed delineation tools were developed that can help farmers identify the area needed to develop livestock farm and comply with statewide nutrient management plan requirements. The ArcGIS-based tools delineate a manureshed based on a user-defined location for a new livestock farm and the desired animal quantity or manure hauling distance. For the third objective, a quantitative evaluation of the impacts of manure application on nutrient loss from the potential areas and an evaluation of the land-suitability framework developed in the first objective were conducted. An ecohydrological model, Soil and Water Assessment Tool (SWAT), was used to quantify nutrient loss from landscapes under various fertilization and land management practice scenarios. Two scenarios were developed with inorganic fertilization and manure application under current land use distribution in the study watershed. The case study watershed included row croplands and forage lands which were modeled as corn grain and alfalfa crops respectively. Simulation results, in general, indicated higher organic nitrogen (N) loss and lower mineral nitrate (NO3) loss with manure application scenario compared to the inorganic fertilization scenario. Alfalfa cropping areas simulated with high nitrogen loss compared to corn areas since the model simulated high crop residue mineralization after the killing operation, which made N available for loss via both surface runoff and leaching during that period with minimal soil cover. Phosphorus (P) loss (organic and mineral P) from manure and inorganic fertilization scenarios were similar for both corn and alfalfa areas. Nutrient loss from landscapes was affected by biophysical land characteristics including slope, soil type, drainage class, hydraulic conductivity, etc., which provides scope for precision manure management based on landscape characteristics. Nutrient loss simulated for moderately suitable, less suitable, and not-suitable areas were compared to evaluate the consistency of the land-suitability framework. Nutrient loading from Suitable and Risky Areas was comparable for the manure application scenario. The land-suitability framework considered each vulnerability factor individually to assign a suitability indicator for an area. If an area had at least one vulnerability factor, it was classified as vulnerable to manure nutrient loss. The SWAT simulations represented a combined effect of all biophysical characteristics of landscapes, while the land-suitability framework used each vulnerability factor individually to identify vulnerable areas. An area vulnerable for one factor might be highly suitable based on another factor. The difference in methodologies primarily resulted in limited consistency between two analysis approaches. To better understand the role of various characteristics, play in determining landscape suitability, individual vulnerability factors were assessed separately. Results indicated high correlations among different types of nutrient loss and vulnerability factors. Organic N, organic P, sediment P, and NO3 loss in lateral flow increased with increasing slope. With the increase of NO3 leaching index, NO3 loss via lateral flow and leaching increased. Soil type also influenced the NO3 loss. The SWAT model used in this study had limited capability to define floodplains, riparian buffer zones, and proximity to streams, so the effects of these vulnerability factors on nutrient loss could not be captured explicitly. The analyses demonstrated that neither SWAT nor land-suitability framework could adequately represent all of the biophysical parameters contributing to the risk of nutrient losses following manure application and highlights the need to use multiple approaches to conduct a holistic risk assessment. This study developed a land suitability framework and ArcGIS tools for sustainable manure management and conducted scenario-based analysis to estimate potential impacts on nutrient loss from land-applied manure. The framework and tools developed in this study used readily available data and are transferable to other regions of the United States with minor adaptations. The SWAT-based analysis indicated the strengths and weaknesses of the developed land-suitability framework. The analysis results demonstrated the need for further refinement of the framework. Improved land suitability analysis could further improve manureshed delineation and management. Sustainable manure management, in combination with improved land-use and land-management practices, could help to realize the benefits of manure to soil health while minimizing water quality impacts.