Project Goal: Increase awareness of groundwater pollution relating to improper manure stacking and seasonal high water tables (SHWT) to increase equine farmers’ acceptance and implementation of improved manure stacking.
The project will achieve the above goal with the following objectives:
1.With Delaware Valley University serving as the technical advisor, conduct research on four equine farms to evaluate the extent that nitrogen and phosphorus from manure stacking on earthen surfaces contaminate SHWTs.
2.Develop two educational tools that will highlight key results from the research, one in a format easily digested by equine farmers, and another in a format easily digestible by technicians working in the agriculture conservation sector.
From a regulatory standpoint, Pennsylvania already has specific manure management regulations that prohibit permanent manure stacking on earthen surfaces. In 2012, Pennsylvania updated its manure management regulations for all farms with livestock, regardless of livestock numbers. One of those updates was specific language stating that manure stacking in the farmstead area must be on an improved stacking pad or covered via a roof or a tarp. In the field, especially on equine farms, this regulation causes many farms to be out of compliance with state manure regulations. The scale of the farms affected coupled with skepticism about the validity of the groundwater contamination claim makes enforcement and implementation of improved manure-stacking practices difficult.
As the Bucks County Conservation District (BCCD) received push back from equine farmers about the potential for groundwater contamination resulting from earthen manure stack pads, BCCD began to search for studies confirming this groundwater contamination and manure-stacking connection. A review was conducted of available studies connecting manure-stacking on earthen surfaces with groundwater contamination in soils with seasonal high-water tables (SHWTs). In addition to Web searches for similar studies in the northeastern Unites States, BCCD also queried the following agencies:
- Pennsylvania Department of Environmental Protection’s (PA DEP) water quality department
- Natural Resource Conservation Service’s state soil scientist and state engineer
- Pennsylvania State University’s nutrient management department
Neither the web search nor the interviews with the above agencies produced any evidence of research connecting equine manure stacking and groundwater contamination in situations similar to conditions found in Bucks County.
The most relevant study found was from Penn State University where nitrogen and phosphorus transport was evaluated from in-field stacking of poultry litter on two different soil types – a sandy-loam and a silt-loam (Liu et al., 2015). Interestingly, the introduction of the Penn State study also highlights a lack of research on nutrient losses from manure stacking despite the presence of manure stacking regulations in Pennsylvania. The Penn State study found that phosphorus leaching to groundwater was twenty times higher than phosphorus surface runoff. Nitrogen leaching was forty times higher than nitrogen surface runoff.
However, there are two major differences between the Penn State experiment and equine manure stacking on soils with SHWTs. First, the soil type sampled in the study is very different from Bucks County. The Penn State study evaluated both a sandy-loam and a silt loam. As expected, the sandy-loam, with a drainage class of excessively drained, leached more readily than the silt loam, with a drainage class of well -drained. In contrast, the majority of Bucks County soils are silt loams with a drainage class of somewhat poorly drained, indicating a lower leaching potential than the soils from the Penn State study. In addition to a different drainage class, Bucks County soils have a high presence of SHWTs, a hydrologic feature not present in the soils from the Penn State study. The net effect of leaching potential in somewhat poorly drained soils with the presence of a SHWTs at varied depths has not be studied.
The second key difference from the Penn State study concerns the manure type. Poultry litter is much higher in nutrient content than equine manure. Using Pennsylvania State University’s average nutrient concentrations for manure, poultry litter has a nitrogen concentration three to six times higher than horses, depending on whether it is layer or broiler litter, respectively. Phosphorus concentration in poultry manure is about 12 times higher than horses, regardless of poultry type. Those differences are very conservative figures as the poultry litter nutrient concentrations account for bedding, whereas the horse manure nutrient concentrations do not include any bedding. Thus, actual nutrient concentrations from an equine manure pile would be much lower since it would include sawdust bedding.
To the best of our knowledge, the proposed project will be the first to look at groundwater contamination from equine manure stacked on somewhat poorly drained, silt-loam soils with SHWTs. Our hypothesis is that nitrogen and phosphorus are leaching from unimproved equine manure-stacking and polluting groundwater in somewhat poorly drained soils with SHWTs in southeastern PA.
If our hypothesis is supported by the data collected, then the research conclusions will have broader implications for agricultural operations throughout the Northeast US. Since horse manure is one of the least nutrient dense manures, we believe that groundwater contamination from manure stacking of similar manure types with less bedding (i.e., cow bedded-pack manure) or more nutrient dense manures (hog, poultry) could be assumed where there is unimproved manure stacking on similar sites.
In February 2018, Bucks County Conservation District (BCCD) procured all equipment for the groundwater monitoring wells, soil sample collection and water sample collection.
Ground Water Monitoring Well Design & Installation
In March through April 2018, BCCD installed 12 wells on 4 cooperating farms, see Well-pictures. Three farms were equine, one was a beef operation. BCCD used 4” PVC well screen pipe with 0.010 inch slot openings, see the well-detail attached to this report. Each farm has 3 wells placed at the below locations:
- Directly at the manure stacking location
- Approximately 10 m upslope of the manure stacking
- Approximately 10 m downslope of the manure stacking
A motorized auger was used to help dig the holes for the wells. However, the motorized auger did not perform well if rocks were present in the soil. Likewise, at almost all well locations, a 4” hand auger to was required to complete the final depths required for the hole for the well.
Water samples were pulled a few days after well installation from 9 of the 12 wells. Each water sample was packaged in ice and mailed out to the lab the same day it was pulled. All samples arrived at the lab within 24 hours of sample pulling. Water samples were again pulled from all 12 wells in August for the summer sample and in the first week of December for the Fall sample.
Originally, four equine farms agreed to participate. At the time of well installation, the fourth equine farm decided to not participate. A beef operation was added as a participating farm at the end of April. The wells for the fourth farm did not have water in them during the remaining weeks of spring.
Soil Descriptions & Sampling
From each farm, soil sampling was done at all 12 well locations. Soil sampling locations were the same as the well locations:
- Directly underneath the manure stacking
- Approximately 10 m upslope of the manure stacking
- Approximately 10 m downslope of the manure stacking
For each of the above sampling locations, samples were collected from each soil horizon using a trowel. A 1-inch soil probe was used to collect soil samples. Several probes were conducted in order to get sufficient sample material. A soil description was recorded for each horizon according to standard NRCS procedures including horizonation, matrix color, texture, structure, and presence of redoximorphic features (type, size, amount, and color).
Below are the horizons that were found for each well location:
- A horizon – Vadose zone (unsaturated)
- B1- Vadose zone (if present)
- B2- Saturated zone (below the water table)
Within 24 hours of sampling, soil samples were laid out to dry in order to prepare them for shipping to the lab and to prevent nitrogen loss.
Using the same methods as described above, soil samples were again pulled from all 12 well locations in August for the summer sample and in the first week of December for the Fall sample.
Both soil and groundwater samples have been analyzed by Penn State’s Agricultural Analytical Services Laboratory (AASL) located in University Park, Pennsylvania. BCCD and Delaware Valley University (DVU) have chosen specific analyses based on what will produce the most industry-familiar units of measure and thus more meaningful analysis.
Soil Analysis – the following analyses have been completed on all soil samples:
- Nitrate Nitrogen
- Ammonium Nitrogen
- Total Organic Nitrogen
- Mehlich (plant-available) Phosphorus
All three nitrogen analyses were completed in order to determine the dominant form of nitrogen in the soil and water. Each form of N has different chemistry, mobility, and environmental impact.
Mehlich P is the standard test for plant-available phosphorus across the state of Pennsylvania. Technicians working in the agricultural conservation and nutrient management sector are familiar with this unit of P measurement. They will have a baseline from which to compare our results.
Groundwater Analysis – the following analyses were completed on all groundwater samples: pH, total dissolved solids, nitrate-nitrogen, alkalinity, aluminum, iron, manganese, phosphorus, sulfate, and hardness. Although not originally planned in the proposal, ammonium, nitrogen was also added to the water sample analysis.
Discussion of well installations & water sampling
Hole digging for well installation was much more time consuming than originally anticipated. Heavy clay soils and channery soils made for difficult digging. Water sampling with the 3″ PVC baler was very simple. A bungee cord was attached to the baler to allow it to be lowered into and pulled back out of the well.
The color of the water samples varied dramatically from the upslope, manure pile and downslope manure pile wells. In June 2018, Farm #1 installed a concrete roofed stack pad at the location of the original, earthen manure stacking area. The well at the manure pile was removed just before construction. Roughly two months after completion of the roofed stack pad, a water sample was pulled from the upslope and downslope wells from Farm #1. The color difference in the downslope well sample from before and after the improved manure stack pad was installed is quite stark. See Farm-1-Before-After photo. The analysis of nutrient contents in the water will determine whether color corresponds to higher nitrogen and phosphorus concentrations.
Due to the wet summer conditions, water was found in all 12 pipes during the August 2018 water sample collection.
Education & Outreach Activities and Participation Summary
On June 12, 2018, BCCD presented the rational and project design for the SARE grant studying effects of manure stacking on soils with seasonal high water table at Pennslvania’s Department of Environmental Protection’s (DEP) quarterly Roundtable Meeting. The audience of Roundtable Meetings is regional DEP and conservation district staff from 5 counties. BCCD connected the grants connected the grant’s relevance to Pennsylvania’s manure management regulations (Chpt 91/ Act38).