Project collaborators in Northwest Arkansas conducted field and economic investigations to compare the impacts of continuous and rotational grazing practices on soil and water quality on lands receiving manure applications.
Field research studies were used to examine the impacts of grazing practices on nutrient runoff, soil erosion, pasture growth and diversity, as well as on soil chemical, physical, and biological characteristics. This information was then used to assist farmers to implement productive grazing practices that protect water quality through the development of a water quality checksheet for pastures.
The results were also used to modify weighting factors for the Arkansas Phosphorus Index.
- Evaluate the effects of year-round grazing management on pasture hydrology, nutrient loss associated with surface runoff, soil quality, and animal production.
Evaluate the impact of soil and water quality parameters according to intensity of grazing practices.
Evaluate on-farm and off-farm costs and benefits from grazing the practices under assessment.
Develop a Water Quality Checksheet for Pastures that farmers and agricultural professionals can use to monitor soil and water quality on grazed fields.
Use experimental results to recommend pasture management practices as modifiers in calculating the Arkansas phosphorous index.
Excessive phosphorus (P) runoff from agricultural land can lead to accelerated eutrophication, particularly in freshwater systems where P typically limits primary productivity. However, scarce information is available on the effects of grazing management on P runoff.
The primary objectives of this study were to evaluate the effects of grazing management practices on forage growth, soil physical properties, pasture hydrology, and nutrient, metal, and sediment loads in runoff from pastureland receiving broiler litter.
Field studies were conducted on 15 small watersheds (0.14 ha each) near Booneville, Arkansas. The watersheds were hayed during year 1 when background data was collected. During year 2, five management strategies were evaluated; (1) hayed, (2) overgrazed, (3) rotationally grazed, (4) rotationally grazed with an application buffer, and (5) rotationally grazed with a fenced riparian buffer. Broiler litter was applied during year 2 at a rate of 5.6 Mg ha-1 (2.5 tons acre-1).
Runoff amounts were correlated to soil bulk density and ranged from 2.7 to 9.2 cm and were highest from the overgrazed watersheds. Likewise, P loads and sediment runoff were highest from overgrazed watersheds and lowest from grazed watersheds. Total P (2.39 kg P ha-1), total nitrogen (TN) (4.4 kg N ha-1), and total organic carbon (TOC) loads (15.2 kg C ha-1) were highest from overgrazed watersheds and were lowest from hayed watersheds (0.82 kg TP ha-1, 1.62 kg TN ha-1, and 5.31 kg TOC ha-1).
Sediment loads in runoff were greater from overgrazed watersheds (55 kg ha-1) than the other treatments, however, soil losses due to erosion were low overall.
Soil bulk density increased as grazing pressure increased and was lowest under hayed conditions. Runoff volumes were highly correlated to bulk density. Percent cover and forage production were inversely related to stocking density, with hayed watersheds having the highest yields.
These results indicate that pasture management influences a wide range of parameters, including forage yields, hydrology, and nutrient runoff.
Educational & Outreach Activities
A University of Arkansas graduate student, John Pennington, used the results from this research in his master’s thesis. He also collaborated with Dr. Philip Moore of USDA-ARS to submit a referred publication based on this work. This paper was submitted to The Journal of Environmental Quality in December 2006.
The paper focused on 1) Impact of grazing intensity on soil nutrient content and nutrient concentration in runoff, 2) Impact of grazing intensity on soil bulk density and quantity of runoff, and 3) Impact of grazing intensity on forage coverage and species variability. Pennington also presented the results from this project at the 2005 meeting of the Society of Soil Science and Agronomy.
Upon the conclusion of the field research, NCAT staff developed a sixteen-page publication titled Water Quality Checksheet for Pastures. This checksheet was designed to help ranchers incorporate environmental protection into their management objectives, and to help stimulate critical thinking as they evaluate the impacts of your land management practices on soil and water quality and consider various risk factors for phosphorus runoff.
A series of questions in the checksheet is designed to increase awareness rather than serve as a rating of management practices. It will help ranchers identify areas of pasture management that need improving, as well as to define areas of strength in their current management practices. NCAT plans to disseminate the checksheet through the ATTRA-National Sustainable Agriculture Information Service
The checksheet contains the following highlights for farmers and ranchers take into account when considering water quality:
Every farm is part of a watershed. Water flows onto and off of the farm.
Management practices on your farm impact the water quality of your entire watershed.
Phosphorus (P) runoff is a leading cause of water quality problems.
Excess P from manure and fertilizers is lost into surrounding waters due to runoff, erosion, and improper fertilizer application.
Soils should be tested to determine levels of P, and to identify pastures that have excess P and are susceptible to runoff.
Knowing the levels of P in your soils is essential for proper manure/fertilizer applications that will protect your watershed from high levels of P runoff.
Depending on where you live, manure applications are based on agronomic P requirements; environmental threshold of soil P; or a P Index.
Pasture management practices affect rainfall runoff and erosion.
Management of riparian areas affects erosion and water quality.
Pastures with continuous livestock grazing, poor forage stands, compacted soil, or steep slopes are more prone to P loss.
The Arkansas P index was developed for pasture systems fertilized with animal manures. It includes grazing management transport factors, which are 0.1 for fields that are hayed only, 0.2 for fields that are both hayed and grazed, and 0.3 for fields that are grazed only.
In other words, fields that are hayed will have a lower P index than those that are grazed if all other factors are the same.
The grazing weighting factors in the Arkansas Phosphorus Index were adjusted utilizing data from this SARE-funded research. Instead of using the three weighting parameters that were in the original Arkansas Phosphorus Index (hayed, grazed and hayed, and grazed); three new categories were developed (hayed, grazed, and over-grazed). The weighting factors for these three parameters were developed by comparing actual P loads in runoff to the Phosphorus Index values. This analysis showed that the P index values needed to be increased by approximately 10% for grazed pastures and 50% for overgrazed pastures. In order to accomplish, the weighting factor for grazed pastures was increased from 0.3 to 0.4 and the weighting factor for over-grazed pastures was set at 0.8.
With the current Arkansas P index growers do not get credit for buffer strips unless they are fenced, since NRCS definition calls for a fence. The data from this study shows unfenced buffers reduce P runoff. Hence, another revision that will be added to the Arkansas P index is another best management practice (BMP), which will be referred to as a setback. This will in fact be an unfenced buffer strip.
Dr. Harold Goodwin, Jr. Director of TEAM Solutions LLC in Springdale, Arkansas, conducted the economic analysis for this performance target.
Water quality issues precipitated by rapid population growth and continued land application of poultry manure at levels exceeding plant uptake of phosphorus have become the focus of economic, environmental and political debate in nutrient-surplus watersheds in Arkansas. This research project concentrates on alternative management strategies that would perhaps sustain the practice of land application of poultry manure without adversely affecting water quality in the region of concern. Broadly, the research objectives encompass the hydrologic properties, soil structure, forage quantity and quality and water quality in runoff resulting from hay production, conventional beef cattle grazing and rotational grazing of varying intensity. Economic consequences of each alternative on both the farmer and the agency providing technical and monetary resources are estimated and compared. Rates of return for each party are also estimated based upon economic assessments of the alternative systems.
This specific performance target involves use of several sets of data, both observed and generated, to quantify yields, prices, costs, revenues and profits under differing states of nature based upon historic prices and existing costs of production
Based upon the experimental data derived from the NCAT/SARE study of forage and grazing management systems, Arkansas historical data on yields and prices for hay and beef cattle and the risk assessment outlined herein, the most economically and environmentally sustainable system is intensive rotational grazing utilizing EQIP cost-sharing funds. This recommendation is based upon the selecting the system with the highest net revenue potential and the lowest amount of nutrient runoff. Selection of this system is dependent upon the management capacity, health and location of the operator and continuation of market conditions present during the period 1985-2005.
The market utilized in this historic assessment is the traditional auction market. Currently, there are no specialized niche markets that have developed to the extent necessary to place sustainably-produced beef cattle. That is, the market for these cattle will require development of slaughter capacity so that the specialized beef can be appropriately differentiated from commercial beef.
Use of increased levels of environmental management by forage and cattle producers that reduces nutrient runoff may be desirable from a societal-good viewpoint. If this were to be the case, public infusion of funds to offset potential income lost by producers undertaking more intensive environmental management systems could provide adequate incentives to establish the necessary revisions in traditional systems to achieve these same societal objectives.
Further research is needed to determine the exact cumulative environmental effects of the recommended management system on a larger area of the watershed so that the economic effects of improved runoff management can be estimated. Once this is accomplished, a return of investment to environmental improvements in forage management systems facilitated through EQIP funds can be determined, yielding a quantifiable measure of societal benefits from governmental assistance aimed at improving the agricultural systems investigated in this research. Findings of previous studies in other geographic regions of the U.S. are consistent with results of the case approach utilized in this research and suggest that this analysis was robust.