A learning system was organized to develop and evaluate pathways for exporting manure P and N from impaired to less impacted watersheds through turfgrass sod. The system comprised livestock and turf producers and research and extension faculty who met throughout the 3-yr project to plan, conduct, evaluate, and disseminate research. In addition to sustaining their learning system, project participants developed and evaluated production practices, environmental impacts, and the operational and economic feasibility of integrating nutrient management between livestock and turf industries. Replicated field experiments and sampling of on-farm and pilot-scale production fields indicated a large percentage of applied manure P could be exported in a single sod harvest. In addition, the portion of P lost in runoff from transplanted, manure-grown sod was less than 50% of that lost after surface applications of composted manure or fertilizer during turf establishment. Moreover, a manure P rate of 191 kg ha-1 during sod production eliminated requirements for P fertilizer after manure-grown sod was imported, but runoff losses of total dissolved P were no greater than imported or established sod top-dressed with typical rates of fertilizer P. Economic analyses indicated composting and hauling costs were constraints on use and export of manure P and N through sod. Yet, net returns to sod production were similar between manure-grown and fertilizer-grown sod located on land near dairies. Moreover, the high value of sod increased potential profits for dairies on which sod was grown.
Three research objectives were developed for a three-year project that expanded the scope of the planning project: 1.) Expand and sustain the learning system of stakeholders during development and evaluation of an infrastructure for using and adding value to manure sources of N and P, 2.) Develop and evaluate an integrated dairy and turfgrass system that will use and minimize losses of manure sources of N and P during sod production, export, and transplanting, and 3.) Analyze and evaluate the operational and economical feasibility of exporting manure sources of N and P from watersheds through turfgrass sod.
Clustering of confined animal feeding operations (CFOs) has contributed large feed imports, nutrient loading on surrounding land area, and potential nonpoint-source pollution of surface waters. Many states have developed recommendations for rates of manure nutrients to prevent accumulation in soil and losses in surface runoff. In addition, advisory committees have joined with regulatory agencies to establish total maximum daily loads (TMDLs) for P and other potential contaminants of bodies of water on impaired watersheds. For example, a TMDL approved for the Upper Bosque River in Texas mandated a 50% reduction in soluble reactive phosphorus loading on the watershed.
The management of P loads on fields and watersheds according to agronomic and regulatory limits appears to be a simple matter of balancing P imports with exports. Yet, there are economic implications when constraints are imposed on manure rates applied to fields adjacent to animal production. In many areas dominated by animal agriculture, there is simply no economically viable alternative to land application. The cost of transporting manure more than short distances from the site of production often exceeds its nutrient value.
On the Upper North Bosque River watershed, transport of manure to composting facilities and of composted manure to other watersheds is subsidized by state and federal funds. Amounts of manure hauled and composted during the first 18 mo of this three-year subsidy program were 150% of the projected program goal. The limited duration of subsidy programs and uncertain long-term markets for composted manure raise questions about the sustainability of direct exports of P in composted manure over long distances.
The export of manure sources of P through turfgrass sod and as composted manure for turfgrass production on other watersheds provide more sustainable options than subsidized transport of composted manure to public-works projects. For example, the relatively large economic value of turfgrass sod could pay the costs of manure export from dairies and impaired watersheds without subsidies. In addition, the large economic value of turf on developing urban landscapes could balance hauling costs and justify imports of composted manure for turf establishment.
A learning system was organized under support of a SARE Planning Project to integrate turf and livestock production, reduce nutrient loads on farms, protect environmental quality, and improve the economic viability of animal agriculture. Stakeholders from the dairy and turfgrass industries, regulatory agencies, and research and extension agencies were organized to develop and evaluate a system exporting manure sources of nutrients through turfgrass sod from impaired to less impacted watersheds. Members of the learning system met throughout the duration of the project to plan, conduct, and evaluate replicated studies of turf and soil responses to composted dairy manure and P and N exports and imports through turfgrass sod. The learning organization and system provided a framework for cooperation among stakeholders from two established production systems in which owner-operated farms still predominated. This people-centered system provided an opportunity to link agricultural and urban development to social, economic, and environmental contexts. In addition, critical conversations among participants from dairy and turfgrass sod industries helped to sustain the learning system while achieving their mutual interests.
In addition to replicated field studies, on-farm demonstrations and watershed-scale evaluations of economic and environmental impacts of export and import of composted dairy manure through sod were needed. The learning system offered an opportunity to forge collaborations between livestock and turfgrass sod producers in on-farm demonstrations that answered questions specific to their respective groups. In addition, university faculty provided access to simulation models that could be used to evaluate watershed-scale evaluations of systems for moving manure nutrient through turfgrass sod. If turfgrass is produced near concentrated animal feeding operations (CAFOs), sod harvests can remove excess manure P originating from feed imports. Initial field studies demonstrated a single sod harvest removed and exported 46 to 77% of manure P applied during production of three turf species. Estimates for an impaired watershed indicate 250 ha of turfgrass sod grown with composted manure can export 50,000 kg of manure P annually.
Despite the potential benefits of exporting manure sources of P through sod or composted manure, the systems could contribute to environmental contamination. Both soluble and sediment-bound P and N in surface applications of manure can be transported in surface runoff on sloping soils. For example, project investigators observed dissolved P concentrations in runoff approaching 10 mg L-1 after composted dairy manure applications on an 8.5% slope of bermudagrass turf. The P concentrations were greatest during the initial runoff event 3 d after 50 kg P ha-1 was applied as manure. During 8 rain events, total dissolved P loss equaled 7.1 kg ha-1. Although manure sources of P and N were lost in runoff, up to 4 times more dissolved P was lost from plots that received the same P rates as fertilizer. The sources of P and potassium (K) in manure residues could eliminate the need for fertilizer applications after manure-grown sod is harvested and transplanted to urban and other landscapes.
Leaching losses of P and N after application of manure are also possible. The P sorption capacity of soil is not always sufficient to retain P applied in large manure rates. Phosphorus leaching below the 30-cm depth was observed for a range of soil textures when rates of manure and other organic wastes exceeded crop requirements. In contrast, P retention in impervious subsoil layers can limit P movement into groundwater at annual manure rates greater than 500 kg P ha-1 for 10 years or more. Yet, drought periods can open preferential-flow pathways through even fine-textured subsoils, which contribute to mass transport to subsurface drainage pathways for both soluble and particulate P during heavy rain events. In addition, organic forms of P in manured soils exhibit greater downward mobility through subsoil layers than inorganic P.
Even if runoff and leaching losses of nutrients are minimized on the impaired or exporting watershed, P and N imported to another watershed as manure residues in sod or as composted manure could contribute to water quality problems. Imports of manure P and N could be particularly problematic if urbanization is already contributing to nutrient loading that compromises water quality on a watershed. For example, the USGS observed P concentrations in 30% of samples in urban streams on the Trinity River basin near the Dallas Metroplex that exceeded the U.S. Environmental Protections Agency (EPA) standard of 0.1 mg P L-1 during 1992 to 1995. Clearly, the benefits of exporting manure nutrients as composted manure and in sod harvests needs to be weighed against potential impacts of manure nutrients on importing watersheds.
Developing and evaluating learning systems.
The learning system and collaborations among stakeholders in a previous planning project were expanded in the current project. Dairy and sod producers; representatives of public research, education, and regulatory agencies from Texas and Virginia; and other stakeholders participated in project meetings and workshops over a 3-yr period. The project participants represented the academic disciplines of agronomy, agricultural economics, biological and agricultural engineering, animal science, rangeland ecology and management, soil science, and veterinary medicine. An existing model of learning and managing activities was implemented and modified to accommodate new stakeholders concerned about both export and import of manure nutrients on watersheds.
Exports and imports of manure P and N through sod.
Supplies of composted dairy manure were estimated for the Upper North Bosque River Watershed from statistics gathered by the Texas State Soil Water Conservation Board. The potential land area available for sod production and export of manure P and N was quantified for Erath county, which included clusters of large dairies and manure composting facilities on the watershed. Inputs from project participants and various sources of digitized land, soil, and infrastructure data were mapped and analyzed through geographic information systems (GIS). The layers in the GIS database were used estimate areas available for sod production. Potential exports of manure P and N in sod were quantified under field conditions through replicated experiments and pilot-scale demonstrations for multiple locations, soil types, and years. For each experiment, duration of turf establishment or regrowth between harvests, turf quality, total P and N amounts in plant and soil components of sod harvests, and extractable P and N in soil beneath the sod layer were quantified. Plugs were removed from sod during harvest and analyzed to calculate potential exports and imports of manure nutrients ha-1.
Export of manure P and N through turfgrass sod plots.
The initial sod harvest from replicated plots of three turfgrass species produced with manure occurred 14 months after establishment . Two additional years of turfgrass production and export through sod were monitored to evaluate regrowth responses after sod harvest and duration between sod harvests. Six treatments were continued during regrowth and repeated harvests of bermudagrass and bluegrass in a randomized complete block design with 4 replications. Manure rates that delivered 100 or 200 kg P ha-1 annually, with and without supplemental N fertilizer, comprised four of the replicated treatments. The manure treatments were compared to an unfertilized control and to a fertilizer treatment (270 kg N and 50 kg P ha-1 y-1).
Tifway bermudagrass and Reveille bluegrass were established on a dairy waste-application field of the Harold Pack Dairy on the Upper North Bosque River Watershed. Starting soil-test P concentrations were greater than 200 mg P kg-1 soil. The treatments for each sod harvest comprised an unfertilized control and applications of 200 kg P ha-1 as composted dairy manure with and without nitrogen fertilizer.
Pilot-scale turf responses and manure P and N removal in sod were quantified on two 1.6-ha production fields of Tifway Bermudagrass in collaboration with a commercial turfgrass sod consortium, Turgrass America. Sod was produced with or without composted dairy manure, plus N fertilizer, to maximize turfgrass growth rates. Two sod harvests were produced within a span of 1.5 yr.
Losses of manure P and N after imports of sod or composted manure.
Manure and fertilizer treatments were installed on replicated plots and lysimeters that were instrumented to evaluate P and N losses during turf establishment. The concentrations and content of P and N forms in runoff and leachates were compared to amounts in soil, manure applications, and transplanted sod. In addition, the plot data were used as inputs and for calibration of watershed-scale, nonpoint-source simulations of P losses to leaching and runoff in collaboration with members of the learning system.
Plot-scale monitoring of P and N losses in runoff after natural rain.
A randomized complete block design comprising three replications of seven treatments was used to evaluate runoff losses from transplanted sod and vegetatively propagated Tifway bermudagrass on an 8.5% slope during turf establishment. Three treatments were composed of ‘Tifway’ bermudagrass sod transplanted from plots that received 100 or 200 kg P ha-1 y-1 as manure or 50 kg P ha-1 y-1 as fertilizer. The same rates and sources of P applied in two split applications to newly-sprigged bermudagrass provided three additional treatments. These six treatments were compared to a control of established bermudagrass sod that received no P inputs.
Runoff was sampled during 14 rain events that resulted in runoff from all plots during turf establishment. Volumes and dissolved and particulate P and N concentrations of runoff collected in 311-L tanks were measured for each runoff event. Runoff samples were filtered (<0.7 mm) within 24 h and stored at 4oC. Filters were dried to quantify sediment weights and allow digestion and analysis of total P and N.
Leaching losses of P and N were monitored in 4 replications of 3 treatments imposed on box lysimeters to assess environmental impacts of imported sod, composted manure, and fertilizer. Two treatments comprised bermudagrass sod transplanted from plots that received either manure P (100 kg P ha-1 y-1) or inorganic P (50 kg P ha-1 y-1). A third treatment was manure P (100 kg P ha-1 y-1) applied with newly-planted bermudagrass sprigs. The lysimeters were filled with a sandy soil consistent with United States Golf Association green construction standards. Simulated rain amounts that exceeded field capacity were applied on three dates during each of three sets of leaching events. Simulated rain was applied 1 week after the start of each set and after each of two applications of N fertilizer (25 kg N ha-1) at 3-week intervals.
Leachates from a 700-cm2 circular portion of turf surface were sampled through a buried PVC cap and drainage outlet. In addition, percolate from the remainder of the lysimeter surface was sampled through slotted PVC pipe at the bottom of boxes. Translucent roofs excluded natural rain and simulated rain was pumped from an irrigation well through 4 square-pattern nozzles over each lysimeter.
Concentrations of total and extractable P (deionized water and acidified NH4OAc-EDTA) and N forms in the sand medium and in imported sods and composted manure were analyzed before treatments were applied on box lysimeters. At the end of each set of leaching events, the surface layer (5-cm depth) and selected depth intervals of the sand medium within box lysimeters were sampled, extracted, and analyzed.
Losses from pilot-scale fields.
Runoff and leaching losses of P and N were quantified on two pilot-scale production fields of ‘Tifway’ Bermudagrass. One pilot-scale field received 75 and 100 kg ha-1 of manure P and supplemental N and K to maximize turf growth rate during two production periods. A adjacent field provided a control. The slope of each field toward collecting gutters and flumes was 1%. The H-flumes and automated samplers installed in each field allowed monitoring and sampling of runoff volumes for P and N analysis during rain events. Groundwater of the pilot-scale fields was monitored in 9 well nests installed in a 3 x 3 grid.
Runoff from the paired fields was monitored and sampled during 16 rain events over the period from September 2002 to March 2003. Concentrations of P and N forms in samples collected throughout each runoff event were analyzed. Runoff samples were filtered (<0.4 mm) and analyzed. Soil of each field was sampled to a 5-cm depth before and after manure applications and after rain events that caused runoff to quantify P and N concentrations near the surface. Concentrations of P and N forms in groundwater beneath bermudagrass fields was sampled and analyzed before each manure application and after sod harvest. Soil of pilot-scale and replicated runoff plots and lysimeters was sampled and composited within selected depth intervals at the start and end of periods of runoff or leachate collections.
Analysis of composted manure and soil.
Samples of manure sources and soil were digested according to a modified Kjeldahl method. The total N in digests was measured colorimetrically. Concentrations of total P in digests were analyzed through inductively coupled plasma optical emission spectroscopy (ICP). The acidified NH4Oac-EDTA method was used to extract plant-available P from compost sources and soil. The NO3-N in compost and amended soil was extracted in KCl solution. In addition, NO3-N and P in compost and soil was extracted in distilled water to quantify nutrients susceptible to loss through leaching and runoff. Water-soluble P in manure and amended soil was previously identified as an indicator of dissolved reactive P concentrations in runoff. An auto-analyzer was used to quantify NO3-N in extracts through cadmium reduction. Molybdate-reactive P (inorganic P form) in extracts of compost sources and soil was determined colorimetrically.
Analysis of runoff and leachates.
Volumes and dissolved concentrations of total P and molybdate reactive P and total N and NO3-N were quantified for leachates from box lysimeters and runoff from replicated plots and pilot-scale fields. Runoff and leachates were filtered and filtrate and sediment fractions were digested. Total N and P were analyzed as described for compost and soil. In addition, NO3-N and molybdate-reactive P in filtrates of leachates and runoff were measured as described for extracts of soil and compost sources.
Statistical analysis of field experiments.
The measured variables were compared among treatments, rain or irrigation events, sampling dates, and monitoring periods through analysis of variance and mean separation techniques. Data from replicated runoff plots and box lysimeters were used to relate concentrations and content of P amd N forms in runoff and leachates to runoff volumes and to amounts of P and N forms in soil, composted manure, and transplanted sod. In addition, the plot and field data were used to develop inputs for calibration of components of simulation models of transport processes on watersheds in Texas and Virginia.
Operational and economic feasibility.
Drs. Wolfe and Bosche from Virginia Tech used nonpoint simulation models to evaluate P and N losses through runoff and leaching on a watershed scale. Wolfe evaluated the GLEAMS model for simulating the fate of nutrients from manure-grown sod. Stochastically-generated weather data and long-term weather records from central Texas were used for daily updates for short- and long-term simulations of nonpoint losses of P and N after manure applications to sod. Observed runoff and leaching losses from field experiments were used to validate the nonpoint simulation model during the two years of the project.
Drs. Lard and Bosch evaluated the economic feasibility of the sod and dairy enterprises. Standard enterprise budgeting procedures (Boehlje and Eidman, 1984) were used to compare costs and returns between fertilizer and manure sources of N and P in the sod enterprise. In addition, enterprise budgets of dairies were developed to assess net returns with and without the system for exporting N and P through sod. Price and yield risks were elicited through analyses of the field studies and through meetings among project participants. Price and yield distributions were constructed from the elicited prices and yields using a distribution-fitting program, Bestfit (Palisade Corporation, 1998b).
P and N export through sod.
The comparative amounts of P and N among clippings and plant and soil components of sod illustrated the principal advantage of exporting manure P and N through sod. As manure rates doubled, increases in P and N removal were most pronounced for the soil component of sod, which included manure residues. Increases of P and N amounts in clippings and in shoots and roots of sod were relatively small compared to the increases in the soil component.
Corresponding increases between P rates applied in manure and P removal in sod will help CAFO’s and turf producers comply with mandates for reduced nutrient loading on fields and watersheds. This BMP, which removes manure residue and P and N in direct proportion to application rates, can raise the regulatory upper limit for P and N amounts applied and removed through annual crop harvests. Percentages of applied P and N in harvested sod were similar for the two manure rates with and without added N for each species, but differed among turf species for each P (46 to 77%) and N (36 to 47%). The large amounts and percentages of manure P and N removed a sod harvest support the feasibility of this BMP in efforts to reduce nutrient loads on watersheds.
Large, P-based rates were applied in replicated experiments on experiment stations and dairy farms to achieve export of large P amounts through each sod harvest. Up to 286 kg ha-1 of P in manure residues and soil was exported with a single harvest of turfgrass sod produced with 325 kg of P top-dressed as composted manure. Similar P amounts were exported as soil and manure residues in sod produced on a dairy waste application field. In addition, up to 274 kg ha –1 of P accumulated in soil through wastewater application was exported with the sod layer. Studies of bermudagrass and bluegrass sod production over a 3-yr period indicated the time required to produce a sod crop and sod quality were comparable between turf produced with composted dairy manure plus supplemental N fertilizer and turf receiving recommended rates of inorganic fertilizer.
Previous regulatory limits on land application of manure were based on expected P and N amounts removed in aerial parts of harvested crop plants. These limits could be increased substantially through removal of manure residues with the soil component of sod harvests. Moreover, increasing the rates of inorganic N applied with composted manure to levels greater than the present study could increase turf growth rates and enable harvest of more than one sod crop per year. The 200 kg P removed in 1 ha of bermudagrass sod represents the total P excreted annually in the manure of 10 dairy cows.
Composting of manure prior to application avoided odors, volatilization losses of NH3-N, and high counts of pathogenic microorganisms associated with surface applications of fresh dairy manure. In addition, the dried, granular texture of composted manure was easier to mechanically dispense on plots. Incorporation to a soil depth of 15 cm prior to turf establishment would overcome problems identified for raw manure and would allow application of larger P and N rates than surface applications. Several turf crops could be produced to remove and export the layers of P and N incorporated from one large manure application.
Runoff losses from pilot-scale production fields.
Runoff volumes of the control field without composted manure were 19% greater than the field with manure during a period in which rainfall totaled 652 mm. The mean runoff to rainfall ratio was 46% for the control and 39% for the turf field top-dressed with composted manure. In contrast, runoff loss of total P from the control field during the monitoring period was 2.8 kg ha-1 less than the turf field supplied 75 kg P ha-1 as composted manure. The composted manure application increased soil-test P concentrations from 138 to 204 mg kg-1, which was 78 mg kg-1 greater than the control field near the final runoff sampling before sod harvest. A linear increase of runoff P concentration was observed as soil-test P increased over 4 sampling dates spanning the dates of manure application. In contrast, soil-test P and P concentrations in runoff from the control plot changed little over the same dates. The relatively small increase in runoff loss of P (3.7 %) attributed to manure P application indicates topdressing and export of manure P through sod is feasible on slight slopes of sod production fields.
Runoff losses after import of manure sources of P and N.
Monitoring of runoff during fall and spring phases of turf establishment illustrated three advantages of importing manure P through sod rather than as surface applications of composted manure. First, bermudagrass turf established more rapidly from imported sod produced with manure than from sprigged treatments top-dressed with composted manure or fertilizer P. Second, import of sod produced with manure eliminated imports and topdressing of fertilizer or manure P during turf establishment. This import of manure P with sod rather than as surface applications on sprigged surfaces minimized runoff loss of TDP during fall and spring. In addition, runoff loss of manure P from imported sod during spring was less than the conventional practice of top-dressing fertilizer P during spring on imported sod produced with fertilizer.
The third advantage concerns P retention within imported sod. Percentages of imported P lost in runoff from transplanted sod were a fraction of percentages lost after surface applications of composted manure or fertilizer during turf establishment in fall and spring. At similar soil-test P levels, runoff losses of manure P from imported sod were less than one half of losses from sprigged plots top-dressed with composted manure.
In addition to advantages specified, observations during 12 of 13 runoff events provided information relevant to export and import of composted manure through sod. A manure P rate of 191 kg ha-1 during sod production will eliminate requirements for P fertilizer after manure-grown sod is imported, but runoff losses of TDP will be no greater than imported or established sod top-dressed with typical rates of fertilizer P.
Losses of TKN or NO3-N in runoff from sod produced with manure were similar to imported sod produced with fertilizer P. The N losses from all treatments were small and mean NO3-N concentrations in runoff were less than the drinking water standard of 10 mg NO3-N L-1.
Sites suitable for the production of turfgrass within the Upper North Bosque River were identified through GIS mapping and analysis. Over 5,000 ha were verified as suitable for turfgrass production. The area available for sod production could support removal of P excreted by 20,000 cow equivalents, more than half of the dairy cows in the watershed. This potential annual export from 5000 ha exceeds the TMDL goal of “an average overall reduction of approximately 50% in soluble reactive P average total-annual loading”.
Drs. Wolfe and Bosch at Virginia Tech used simulation modeling in watershed-scale evaluations of water quality impacts of dairy manure use in a sod enterprise. Specifically, modeling work at Virginia Tech built upon the field work conducted at Texas A&M University. Nonpoint simulation models evaluated P and N losses through runoff and leaching for various manure and fertilizer rates, slopes, and soil types during production and after sod is transplanted. The project work used the GLEAMS nonpoint source (NPS) pollution model for establishing turfgrass on dairy producers’ fields. The simulations complemented the field experiments conducted in Texas. Treatments applied in the field included control, low, and high rates of P applied as composted dairy manure and two rates of inorganic P fertilizer. Runoff was collected during natural rainfall events during an approximately sixteenth-month period.
The model was calibrated successfully for runoff; thus allowing the performance of the model in estimating nutrient losses to be evaluated independently of the runoff estimates. GLEAMS predicted dissolved losses for all events fairly well except for the Spring 1999 time period. Poor predictions for one event during that time period affected the results for the whole time period. In general, dissolved losses were underestimated for all treatments. Sediment-bound nutrient losses were measured for two periods in the field. The model predicted sediment-bound N losses more accurately than sediment-bound P losses. In general, N losses were predicted more accurately than P losses. Based on the overall results, it appears that GLEAMS could be used to evaluate losses from newly established sod.
Educational & Outreach Activities
Choi, I., C.L. Munster, D.M. Vietor, R.H. White, C.E. Richards, G.A. Stewart, and B. McDonald. 2003. Use of turfgrass sod to transport manure phosphorus out of impaired watersheds. P. 518-526, In A. Saleh (ed) Proc. of Conference, Total Maximum Daily Load Environmental Regulations II. ASAE, St. Joseph, MI.
Gaudreau, J.E., D.M. Vietor, R.H. White, T.L. Provin, C.L. Munster. 2002. Response of turf and quality of water runoff to manure and fertilizer. J. of Environ. Qual. 31: 1316-1322.
Hanzlik, J.E., C.L. Munster, A. McFarland, D.M. Vietor, and R.H. White. 2004. GIS Analysis to identify turfgrass sod production sites for phosphorus removal. Transactions of ASAE: (In Press)
Hanzlik, J., C. L. Munster, D.M. Vietor, and R.H. White. 2002. Location of turfgrass production sites using GIS in the North Bosque River watershed, Pages 472-476. In Proceedings of ASAE Conference on TMDL Development and Implementation. Fort Worth, TX. March 11-13.
Vietor, D.M., T.L. Provin, R.H. White, C.L. Munster. 2004. Runoff losses of phosphorus and nitrogen imported in sod or composted manure for turf establishment. J. of Environ. Qual. 33: 358-366.
Vietor, D.M., E.N. Griffith, R.H. White, T.L. Provin, J.C. Read. 2002. Export of manure P and N through turfgrass sod. J. of Environ. Qual. 31:1731-1738.
Vietor, D.M., T.L. Provin, S.E. Feagley, R.H. White, and F.J. Jacoby. 2003. On-farm demonstration of effectiveness of export and import of composted dairy manure through turfgrass sod. P. 494-499, In A. Saleh (ed) Proc. Of Conference, Total Maximum Daily Load Environmental Regulations II. ASAE, St. Joseph, MI.
Vietor, D.M., R.H. White, C.L. Munster, and T.L. Provin. 2002. Reduced non-point source pollution through manure use and export in turfgrass sod, Pages 396-400. In Proceedings of ASAE Conference on TMDL Development and Implementation. Fort Worth, TX. March 11-13.
The learning system of this project has provided technical information and fostered development of collaborative ventures between livestock and turf producers. For example, the joint venture in zoysiagrass sod production between Gardner Turfgrass, Inc. and Stoney Point AgriCorp., Inc. emerged from research studies and critical conversations among participants in this project. In addition, new pathways for exporting manure P and N from impaired to less impacted watersheds and between turf and livestock industries are being developed. The turf production and export system of this project is providing an alternative to government-subsidized exports of composted manure from impaired watersheds in Texas. In addition, import of composted dairy manure in a sod product reduces potential runoff losses of P compared to surface applications of inorganic P fertilizer or composted dairy manure on establishing turf.
Drs. Lard of Texas A&M University and Bosch of Virginia Tech provided leadership for evaluations of the economic feasibility of the sod and dairy enterprises. Dr. Lard developed enterprise budgets to compare costs and returns between fertilizer and manure sources of P and N in sod production. In addition, enterprise budgets of dairies were developed to assess net returns with and without the system for exporting N and P through sod. Enterprise budgets developed for sod production in Texas were modified for Virginia conditions to determine the economic feasibility of using dairy manure in place of the conventional use of inorganic fertilizer. There was very little difference between costs for conventional production using inorganic fertilizer versus production using dairy manure; the primary difference being higher inorganic fertilizer expenses for N, P, and K for conventional production. For both budgets, some inorganic nutrients were needed to ensure premium quality of the sod.
The economic feasibility of incorporating a sod operation into a dairy farm was investigated for a representative farm in Virginia. The two alternatives, dairy with sod and dairy without sod, were compared in the context of two nutrient application scenarios; one scenario utilized N-based application rates while the second scenario utilized P-based application rates. The representative Virginia dairy, located in a dairy producing area in the Shenandoah Valley comprised 100 cows with an additional 30 to 40 replacement heifers. For the dairy with the sod enterprise, 50 acres was taken out of corn silage production and put into sod.
For the sod operation, additional income was calculated based on the average cost for sod per yard, assuming 85% of the sod would be harvested. Reduced expenses were associated with reduced labor, equipment, and materials associated with the 50 acres taken out of corn silage to produce sod. Increased expenses included purchase of corn silage to replace what would have been grown on the 50 acres and expenses associated with the sod enterprise. The amount and cost of dairy manure that would need to be hauled off the farm was calculated for the dairy enterprise and for the dairy with sod enterprise if nutrient management switched from N to P based on P crop removal for corn silage. An additional $38,920 in profits was estimated for a typical year for the dairy with sod enterprise compared to the dairy alone when manure was applied on an N basis. An additional profit of $46,209 was estimated for P-based applications.
A joint venture between Mark Quinn of Stoney Point AgriCorp., Inc. and Sam Peterson of Gardner Turfgrass, both members of the project learning system, emerged during the course of this project. Quinn provided land resources, nutrients from feedlot manure and wastewater, irrigation and tillage equipment, and labor while Peterson provided knowledge of turfgrass, specialized equipment, and access to markets for sod. The first crop of Zoysiagrass sod was harvested in 2003 and transplanted to a golf course near Dallas, Texas. Another collaboration occurred among graduate student Brandon McDonald, project investigators, and Ike Thomas of Turfgrass America. Project investigators and SARE support provided land, composted manure, labor, and equipment for irrigation and turf maintenance. Turfgrass America provided turfgrass plugs for establishment, labor and equipment for plugging and harvest of sod, and access to markets for sod. The collaboration among project investigators, students. and Turfgrass America leveraged the support funds awarded from SARE and achieved project objectives. In addition, this joint venture between researchers and the turf industry provided detailed information for economic analyses, including resource requirements for production and export of manure-grown sod.
Areas needing additional study
Enhancement Grant #ES032-012 Ended 3/31/2005
The environmental and economic impacts of exporting and importing manure sources of nutrients through sod need to be evaluated on a watershed scale. In addition, the sources of composted manure or biosolids used and distributed across watersheds through turfgrass sod needs to be expanded. Although dairy feedyards were a principal source of composted biosolids in this project, municipal sources of biosolids and wastewater are potential sources of nutrients and organic matter for turfgrass establishment and production. Economic analyses indicated composting and hauling costs limit the distance between compost sources and turfgrass sod production.
Although cycling of composted biosolids through turfgrass sod offers obvious benefits, environmental impacts of compost application and of sod transplanted from compost-grown turfgrass need to be evaluated. The composition and rates of composted biosolids will affect leaching and runoff losses of nutrients on production fields and on sites where compost-grown sod is transplanted. Variation of concentrations of nutrient forms in composted biosolids contributes to uncertainty about turf responses and environmental impacts. The variation among compost sources and of mass balance of compost nutrients applied to turfgrass needs to be quantified. Observations of nutrient distribution among plants and soil of turfgrass sod and leaching and runoff losses are needed to develop and manage a system for cycling municipal biosolids through turfgrass sod.
Evaluate variation of concentrations of total and extractable phosphorus, nitrogen, and carbon forms among diverse sources of municipal compost.
Compare mass balance of total and extractable phosphorus, nitrogen, and organic carbon forms among sods transplanted from fields grown with contrasting compost sources or inorganic fertilizer.
Establish Tifway bermudagrass on sod production fields with and without composted municipal biosolids.
Evaluation of diverse sources of compost.
Composted biosolids from 10 diverse sources in Texas were collected, analysed, and compared. The diverse sources of biosolids were digested to determine total nutrient concentration. In addition, compost sources were extracted in water (2 g compost in 20 mL water shaken for 1 hr) and Mehlich 3 solution to quantify P and N forms available to turfgrass or vulnerable to transport in percolate through soil. Analyses indicate variation of concentration of P and N forms among compost sources contributes to uncertainty with respect to application rates on turf and potential environmental impacts. Total P varied 100-fold, Mehlich-3-extractable P varied 25-fold, and water-extractable P varied 10-fold among compost sources. Similarly, concentrations of nitrate-N varied 300-fold and Total Kjeldahl N 10-fold. Except for one municipal source of compost (Dillo Dirt), Mehlich-3 P was directly related to total P in the compost sources.
The relationship between water-extractable P and total P differed among compost sources. Although total P was relatively high in three municipal composts, particularly the Dillo Dirt, water-extractable concentrations were relatively low. Except for one compost source that included horse manure, water-extractable P was relatively high in compost sources containing animal manure. Both total and water-extractable P were relatively low in compost derived from plant residues.
The variation of total, Mehlich 3, and water-extractable P forms indicates both turfgrass responses and environmental impacts will differ among compost sources. The analyses suggest that the large, volume-based rates of compost used to amend urban soils and establish turfgrass could be detrimental to water quality for those compost sources high in water-extractable P.
Mass balance of nutrients and carbon in sod transplanted to box lysimeters.
Two municipal sources of composted biosolids that differed two-fold in total P were applied at a large, volume-based rate (1.2-cm depth) during establishment of Tifway bermudagrass. The volume-based compost rate raised mean concentrations of total P within a 2.5-cm depth at harvest to 1139 mg/kg for sod grown with Bryan compost and to 2683 mg/kg for sod grown with Dillo Dirt. Total N concentration in sod grown with respective composts was 3500 and 5530 mg/kg. Total P concentration in the layer of sod grown with fertilizer P was 136 mg/kg and total N concentration was 650 mg/kg.
Sod transplanted from plots grown with the two compost sources or with inorganic fertilizer comprised three treatments within each of four replications on box lysimeters (2.25 sq. m x 0.5 m depth) filled with coarse silica sand. Translucent roofs excluded natural rain from lysimeters. Simulated rain was applied to balance daily evapotranspiration and to achieve mass flow of water through the sod layer and sand medium during six leaching events after sod was transplanted. Leachate was collected 20 cm below the surface within a 30-cm diameter cap and at the bottom (50 cm below surface) of lysimeters through a modified well screen. Leachate volumes were measured and sampled for analysis of total dissolved P, nitrate-N, and dissolved organic carbon before and after each simulated rain event. In addition, total and extractable forms of P and N in clippings, soil and plant components of sod, or the sand medium are being analyzed and integrated with leachate analyses to compute mass balances of P and N.
The sod and sand medium were sampled and analyzed at four depth intervals after the third and sixth leaching event. Mean soil-test P (STP) (Mehlich 3) concentrations for the two sampling dates differed among the three sources of transplanted sod at depths of 0 to 5, 5 to 15, and 30 to 50 cm within lysimeters. The ranking of STP concentrations within the depths sampled below sod treatments corresponded with the ranking of total P in sod transplanted from the fields grown with Dillo Dirt, Bryan compost, and fertilizer P.
Although 50 kg of fertilizer N/ha was applied to all treatments after the first leaching event, nitrate-N concentrations in the 0 to 5-cm depth were two times greater for sod transplanted from compost-grown turfgrass than from fertilizer-grown sod. The compost imported with sod contributed to greater nitrate-N than fertilizer-grown sod in the surface layer, but nitrate-N concentrations at depths below 5 cm in the sand medium were similar among treatments. Similar to observations for nitrate-N, mean dissolved organic C (DOC) concentration in water extracts was greater for sod transplanted from turfgrass grown with Dillo Dirt than sod grown with fertilizer P. In addition, DOC concentrations were low and similar among the three sod sources at depths in the sand medium below 5 cm.
Soil-test P differed among sod sources at depths sampled within the sand medium of box lysimeters, but no increases of total dissolved P concentration or mass were observed in leachate compared to rain water for the three treatments. In contrast, the mass of nitrate-N recovered in leachate accumulated within lysimeter bottoms from daily irrigations prior to each large simulated rain event was greater for compost-grown sod than for fertilizer-grown sod. The mass of nitrate-N recovered in leachate sampled from small volumes recovered in cap samplers at the 20-cm depth was similar among the three sod sources before and after the six simulated rain events.
The DOC extracted from the sand medium at depths below 5 cm did not differ among treatments. Yet, the mass of DOC in leachate collected from the bottom of lysimeters was greater for compost- than for fertilizer-grown sod in samples collected before (cumulative rain) and after each simulated rain event. The mass of DOC collected in small volumes of cap samplers at the 20-cm depth was small and similar among sod sources.
Field-scale comparison of turfgrass sod production with and without compost.
Composted municipal biosolids were purchased for application to one of a pair of 1.4-ha fields after harvest of a current crop of Tifway bermudagrass. The sod fields are surrounded with earthen dikes to contain runoff from a 1% slope during natural rain events. Runoff will be collected in gutters and monitored and sampled in an H-flume for each field. Total dissolved P, molybdate reactive P, nitrate-N, and sediment concentrations and mass in runoff will be sampled and compared between fields with and without compost during turfgrass regrowth. In addition, the sod layer and soil to a 90-cm depth will be sampled and analyzed before and after compost applications and after the sod harvest from each field.
Leaching studies indicate the system for cycling of composted municipal biosolids (CMB) through turfgrass sod was not detrimental to groundwater quality. Although the volume-based rates applied to improve soil physical properties contained large concentrations and masses of total P, water-extractable P concentrations were relatively low for both CMB sources used to grow sod. The low concentrations of water-extractable P in transplanted CMB-grown sod contributed to small increases in STP within the sand medium of lysimeters, but no increases in total dissolved P leaching before and after six simulated rain events over a 5-month period. Imports of CMB in transplanted sod at the volume-based rates used here will not contribute to dissolved P increases in drainage from establishing turfgrass surfaces on urban landscapes.
Compared to fertilizer-grown sod, import of CMB with transplanted sod did contribute to nitrate-N loss in leachate accumulated from daily irrigations prior to each leaching event. Yet, similar to dissolved P, imports of CMB sources of N in transplanted sod were not detrimental to groundwater quality during the six leaching events applied during the 5-month period of sod establishment on lysimeters. At the volume-based rates used here, CMB imports through sod are not a major source of leaching losses of nitrate-N.
Although import of CMB with transplanted sod increased DOC concentration in the surface layer and DOC mass in leachate compared to fertilizer-grown sod, leaching loss of DOC was not associated with mass loss of dissolved P. Transport of DOC in percolate does not effect transport of dissolved P.