In late spring 2011, we began establishment of an on-farm experiment with an organic dairy near Philadelphia, TN. Three forage systems [a) annual system, b) perennial system, and c) a cool-season perennial legume overseeded with a warm-season annual grass] were established in 1-acre plots and replicated. Estimated total herbage yields were similar among treatments, however, percentage of nonsown species differed significantly, with the highest observed in the perennial legume-annual grass system and the lowest observed in the annual system. Results suggest that all systems examined have utility for organic grazing livestock producers, depending on producer objectives and management capabilities.
Organic milk production continues to be one of the strongest sectors of the organic food industry. However, in the U.S., organic dairy production has been concentrated in the upper Midwest and the Northeast. While there is increasing interest in the Southeast in organic dairy production as a way to increase the viability of family farms, there is limited research and extension information from this region to help conventional dairy farmers transition to organic or to help beginning dairy farmers establish their operations. This is especially true in the area of forage management for organic farms, an important issue considering that the USDA National Organic Program specifies that 30% of a dairy cow’s dry matter intake must be supplied through grazing, and that dairy cattle must graze throughout the length of the grazing season. The issue is also of great economic importance to producers given the high cost of organic feed grains.
Research and extension information relating to the production of organic forages for organic dairy production is extremely limited. Further, available information typically relates to forage production systems in cool, continental climates such as northern Europe, the northern U.S., and Canada. Information relating to forage species selection and management from these regions is of limited value to organic forage production in the humid southeastern U.S. where climatic conditions and soil properties differ markedly. While these climatic conditions can provide for a lengthened grazing season, it can be difficult to produce forages of sufficient quality during the hot summer months. Additionally, given that soils in the Southeast are typically low in organic matter, forage productivity without conventional fertilizers can be limited without proper selection of forage species mixtures and appropriate nutrient management.
Selection of forage species mixtures will be a key part of a successful organic forage production program. Forage species vary widely in their yield, chemical composition, and nutrient digestibility (Staples, 1992). Additionally, organic forage production can be constrained by the lack of conventional nutrient and pest management inputs, particularly herbicides for weed control. As such, it is important to investigate forage species and mixtures that have been shown to be aggressive in establishment and growth, as well as forage legumes which will decrease the dependence on nitrogen application.
A second important aspect of forage production for grazing dairies, especially in the Southeastern U.S., is seasonal availability of forage. Forage rotations and mixtures containing both cool and warm-season species will be an important solution to this problem. Annual grass/legume mixtures are an obvious choice, since these forages generally establish relatively quickly, and conventional planting methods allow for the mechanical destruction of weed competition prior to planting. However, the use of only cool and warm-season annuals in rotation creates a difficulty in that twice during the year, there is an establishment period with limited forage production. Additionally, the tillage operations limit accumulation of soil organic matter and increases risk of erosion, which reduces the sustainability of the system. Incorporating perennial forages into the system can help minimize the problem created during annual forage crop establishment transitions.
Forage legumes should increase sustainability of the overall forage program, regardless of the grass species used. Legumes offer an advantage in two areas. First, adequate forage quality to support milk production is often limited for several months of the year and forage nutrient quality can frequently decrease to the point where supplementation is needed (James and Collins, 1992). Legumes are generally higher in protein and energy content than grasses, which will improve the nutrient availability to grazing dairy cattle. Second is the advantage of biological nitrogen fixation. Research has shown that including a legume in a grass mixture can provide an equivalent yield to a grass sward fertilized with 60 to 100 lbs nitrogen per acre (Miller and Heichel, 1995).
The objectives of this study were to (1) examine the performance (yield, forage quality, soil quality, grazing days, botanical composition, and economics) of three organic forage systems for the Southern region (an annual mixture, a cool-season perennial and warm-season annual mixture, and a perennial mixture) and (2) disseminate results to producers and other professionals via a producer field day, extension programming, conferences, and scientific journal publications.
a. Annual system
– Wheat (cv. Overland)-crimson clover (cv. Dixie) followed by sorghum-sudangrass (cv. BlackHawk BMR)/cowpea (cvs. Iron & Clay)
b. Perennial system
– Tall fescue (cv. MaxQ)-red clover- white clover (cv. Rivendal)
c. Cool season perennial legume overseeded with a warm-season annual grass
– Red clover (cv. Cinnamon)-crabgrass (cv. Red River)
Study design and forage establishment:
The six-acre study area was planted to one-acre blocks of each forage mixture at a certified organic dairy near Philadelphia, TN. Each forage mixture was replicated. Warm-season forages were first planted in late spring 2011 following site preparation with tillage by the cooperating producer. Cool-season forages were first planted in fall 2011. Organically-produced seeds were used when commercially available. The site is comprised of Montevallo and Whitwell series soils, with soil textures typically silt loam. Initial soil analyses indicated soil pH 6.8, initial soil organic carbon of 14.8 g C kg-1 soil, total soil nitrogen of 1.3 g N kg-1 soil, and Mehlich 1 P and K of 30 mg P kg-1 soil and 83 mg K kg-1 soil.
The primary use for each pasture was to provide forage through grazing. Each forage species mixture was fenced separately using temporary electric fencing to allow for independent management, and divided into smaller paddocks by the producer throughout the grazing season to improve forage utilization. During periods of the year when excess forage was produced, forage was harvested as stored feed.
A. Yield – Small areas of each pasture were harvested prior to producer utilization to estimate dry matter yield per acre. Sample areas (10, 10 ft2 areas per paddock) were harvested, dried in forced air oven, and weighed to estimate dry matter yield.
B. Forage quality – Harvested forage samples were analyzed for crude protein (combustion), total digestible nutrient content, acid detergent fiber and neutral detergent fiber, as well as mineral content using near infrared reflectance spectroscopy.
C. Soil quality – Soils were sampled in spring summer and fall of each year, beginning in spring 2011 and ending in spring 2013. Soils were analyzed for pH, total nitrogen and carbon, permanganate oxidizable C, and inorganic N.
D. Grazing days – Stocking rates and days grazed were monitored by the producer for each forage species mixture.
E. Botanical composition – Estimates of weed pressure/forage species presence were determined by biomass separations of forage samples collected for yield estimations.
F. Economic analysis – Estimates of cost for forage production, were developed based on measures of forage production and estimates of production costs for presentation at the on-farm field day.
A. Producer field day/pasture walk – On May 7, 2013, a field day was held at the site to show the data collected from the study, as well as give producers the opportunity to see the site first-hand. Grant cooperators (Butler, Bates, Rhea) and University of Tennessee specialists (Krawczel) presented information during a portion of the field day followed by a research site tour/pasture walk. An additional pasture walk was held at the site in cooperation with Organic Valley in 2012.
B. Tennessee Forage and Grassland Council conference – In November, 2013, project results will be presented by Dr. Butler at the TFGC annual conference. This annual conference includes producers, industry and public service individuals from across the state. This conference will provide the opportunity to communicate experiences, conclusions and recommendations that were developed from this project.
C. Organic crops field tour at the East Tennessee Research and Education Center – Information on organic forages was presented by Dr. Bates in 2011, and information on organic forages and weed control by Dr. Butler in 2012 and 2013.
D. Video account of project- Digital video was taken as the project was being conducted. We are currently working to complete a video account of the project and general organic forage production practices for use on UT websites (e.g. http://forages.tennessee.edu and http://organics.tennessee.edu).
E. Publications – Data collected as part of this study is planned to be combined with other ongoing organic forage studies to prepare a publication on organic forage production in the Southeast. Data from this study was presented at the annual meeting of the American Society of Agronomy in 2012. See outreach/publication section for more information.
No significant differences (P > 0.05) among forage system treatments were observed in total dry biomass yield estimated from forage samples harvested over the course of the study (range of 22 to 26 Mg ha-1). However, for biomass of sown species, the annual system had the greatest estimated biomass (25 Mg ha-1), followed by the perennial system (17 Mg ha-1) and then the red clover-crabgrass system (10 Mg ha-1) due to the large percentage of biomass accounted for by weeds and non-sown species in the perennial and red clover-crabgrass systems. Most soil analyses (i.e., soil pH, inorganic N, extractable P) indicated few meaningful differences between treatments. However, there was a trend toward a reduction in total soil C over the course of the study in the annual system as compared to the other two systems which were characterized by less soil disturbance. In the annual system paddocks, total soil C at the beginning of the study averaged 16.9 g C kg-1 soil compared to 12.7 g C kg-1 soil at the end of the study. This compares to an initial value of 13.8 g C kg-1 soil in the other systems at the beginning of the study and 15.8 g C kg-1 soil at the end of the study. While these changes are slight and the limited number of replicates should be noted, it does conform to our expectations in systems with greater soil disturbance via tillage. Analysis of the labile fraction of soil C has so far indicated no differences among treatments, additional samples have been taken in 2013 and are being analyzed currently. For more information on project outreach results, please see outreach/publications section.
Educational & Outreach Activities
1. Butler, D.M.*, and G.E. Bates. Forage production practices for organic dairy operations. 8 Nov 2013. Tennessee Forage and Grassland Council Annual Meeting, Nashville, TN.
2. Butler, D.M.*, and G.E. Bates. Organic forage research at UT. 1 Aug 2013. Organic Valley Pasture Walk, Benton, TN. (~10 attendees)
3. Butler, D.M.*, and G.E. Bates. Organic forage research at UT. 7 May 2013. Organic Forage and Dairy Field Day, Skipping Rock Dairy, Philadelphia, TN. (~ 35 attendees)
4. Butler, D.M.*, S.E. Eichler Inwood, C. Fust and H. Barry. Ecologically-based weed management strategies for organic growers. 24 Apr 2013. Organic Crops Field Tour, East Tennessee Research and Education Center, Knoxville, TN. (~ 100 attendees)
5. Butler, D.M.*, G.E. Bates, S.E. Eichler Inwood, J. Beeler and D. McIntosh. Development and evaluation of organic forage systems for the Southeastern U.S. 17 Dec 2012. Beef and Forage Center Research and Recommendation Meeting, Knoxville, TN. (~ 75 attendees)
6. Butler, D.M.*, and G.E. Bates*. Organic forage research at UT. 1 May 2012. Organic Valley Pasture Walk, Skipping Rock Dairy, Philadelphia, TN. (~ 10 attendees)
7. Butler, D.M.*, G.E. Bates, S.E. Eichler-Inwood and J.E. Beeler. 2011. Evaluation of organic forage production systems for the Southeast. 75th ASA-CSSA-SSSA Annual Meeting Abstracts; San Antonio, TX, 16-19 Oct 2011. (~ 50 attendees)
8. Butler, D.M.*, G.E. Bates, S.E. Eichler Inwood, J. Beeler and D. McIntosh. Interactions between seeding rates and weed control in organic field and forage crops. 26 Apr 2012. Organic Crops Field Tour, East Tennessee Research and Education Center, Knoxville, TN. (~ 100 attendees)
9. Bates, G.E.*, and D.M. Butler. Producing forage crops organically. 28 Apr 2011. Organic Crops Field Tour, East Tennessee Research and Education Center, Knoxville, TN. (~ 100 attendees)
This project effectively demonstrated the establishment of three organic forage systems that have utility for producers in the Southeastern US. In addition to outreach and collaboration with cooperating producers, the project extended results to numerous producers and agricultural professionals through a combination of field days, in-service trainings, pasture walks, and research presentations (see outreach/publications section). Research results in this study have helped University personnel develop organic forage recommendations and have led to the implementation of additional forage research studies on UT’s Organic Farm and additional studies in the planning stages in collaboration with additional personnel at UT and other universities.
Producer feedback was much in line with data collected during the course of the study. The cooperating producers were impressed with the annual system and the high level of weed control achieved in this system. The producers had not previously used cowpea, and were favorably impressed by its productivity, ability to regrow after grazing, and suitability for mixture with annual warm-season grasses. The inclusion of a warm-season legume is an important component of an annual organic forage system, given that these systems are typically limited by N. Other producers in the region who attended outreach events have also expressed interest in cowpea due to the limitations of other warm-season forage legumes. The perennial system was also favorably reviewed by the cooperating producers, as the relatively good weed control compared to the red clover-crabgrass system and the lower level of management as compared to the annual system made this system an attractive choice for more extensive use around their farm. The reduction in soil disturbance is also likely to have a positive effect in reduced soil erosion and potential gains in soil quality. Lastly, while the producers generally liked the red clover and crabgrass system, the poor performance of the crabgrass in the second year and high weed pressure made it less attractive than the other systems. It is likely that this system could be improved through the addition of an annual, cool-season grass (e.g., annual ryegrass) to better compete with winter weeds. Further research may also indicate more effective means of establishing crabgrass in a perennial legume: it may be the case that some soil disturbance is needed to obtain more consistent crabgrass stands to compete with summer weeds. A large number of farmers and agricultural professionals were reached through the project (see outreach and publications section), increasing knowledge and awareness of organic forage production in the region.
Areas needing additional study
Weeds were initially problematic in organic perennial forage establishment. While mowing management during establishment can help to resolve this issue, the potential for increased weed seed production and competition from weeds negatively impacting the establishment of perennial forages is an issue that deserves further study. One potential area of research is on the use of nurse crops (such as small grains) to help facilitate perennial forage establishment in organic systems. While this study was only able to evaluate three organic forage systems at the farm-scale, there are a number of questions that should be answered on the selection and management of competitive and complementary mixtures of forage species for organic production systems. Within forage species, there is a need to evaluate and develop forage cultivars more suited to the unique conditions of organic production systems.
Rotational considerations must also be taken into account when evaluating organic forage systems. While certain forages can be very productive and competitive in organic systems (e.g., annual ryegrass, crabgrass, bermudagrass), producers rotating to annual grain cropping systems may not wish to use these species due to the potential for weediness in those crops. Lastly, this project’s focus on agronomic aspects of organic forage management is an important first step, but further systems-level research is needed to combine these agronomic evaluations with evaluations of grazing animal performance.