Location: Dairy Forage Research
2021 Annual Report
Objectives
1. Develop or improve annual and/or perennial forage production systems that optimize forage production for dairy farms while reducing environmental impacts.
1A. Evaluate management factors for warm-season grass species to develop forage production systems for dairy farms.
1B. Determine manure source and application rate effects on warm season grass productivity, nutritive value, and persistence, and on soil chemical and biological properties.
1C. Determine management and plant biological factors contributing to winterkill and poor persistence of alfalfa and develop strategies to reduce winterkill and improve persistence of alfalfa.
2. Develop or improve warm-season and/or cool-season grass germplasm that enhances yield, quality and resiliency of forage production for integrated dairy systems.
2A. Develop, validate, and apply genomic selection tools to be used in breeding switchgrass for improved forage/biomass yield, cold tolerance, nitrogen-use efficiency, and digestibility.
2B. Determine the role of endophytic fungi in the meadow fescue life cycle.
3. Develop or improve forage legume germplasm that enhances yield, quality and resiliency of diverse forage management systems.
3A. Develop improved red clover varieties that have greater persistence and biomass yield.
3B. Develop improved alfalfa germplasms that are genetically broad and will expand the U.S. alfalfa breeding pool.
3C. Improve underutilized forage legumes for use in forage production and as cover crops.
4. Develop or improve cover crop systems that enhance forage production while reducing nutrient losses and soil erosion in integrated dairy production systems.
4A. Refine management practices for corn grown with interseeded alfalfa.
4B. Develop or identify germplasm that is well suited for interseeding.
5: Develop ration formulation and feeding strategies that experimentally validate chemical methods designed to properly value use of alfalfa in terms of animal performance, milk production, nutrient use efficiency, and enteric methane emissions.
6: Develop cover crop strategies (and tools) for the upper Midwest that explore new plant species and overcome current soil moisture, soil temperature, crop pest and economic limitations to provide incentive to farmers to adopt cover cropping.
Approach
Objective 1. Switchgrass, big bluestem and indiangrass cultivars will be fertilized with 0 to 80 kg/ha of fertilizer nitrogen and harvested once or twice per season to assess plant development, dry matter yield and forage quality in relation to nutrient requirements of dairy cattle. The warm season grasses will also be fertilized with 0 to 80 kg of nitrogen in the form of solid and liquid manure to assess nutrient uptake, soil chemical and biological properties, plant persistence, dry matter yield and nutritive value.
Objective 2. Genomic selection tools will be developed, validated, and used in breeding switchgrass for improved forage/biomass yield, cold tolerance, nitrogen-use efficiency, and digestibility. The role of endophytic fungi in conferring drought, heat, defoliation, and traffic tolerance to meadow fescue will be assessed in greenhouse and field experiments.
Objective 3. An extensive breeding program utilizing phenotypic and genotypic selection of halfsib lines grown as spaced plants and swards at multiple locations will be used to develop red clover cultivars with improved biomass production and persistence. Four alfalfa subsp. falcata syn1 germplasms developed by recurrent phenotypic selection will be harvested for multiple years in sward trials to assess persistence and dry matter yield. Two experimental birdsfoot trefoil varieties differing in tannin content and 15 experimental kura clover varieties will be compared to check varieties in sward trials to assess growth characteristics, dry matter yield, persistence, and forage quality.
Objective 4. Field studies will evaluate and refine agrichemical applications as well as planting and harvesting management practices to improve the establishment and overall forage production of alfalfa interseeded into silage corn. Syn1 and hybrid alfalfa entries developed from surviving plants and various corn hybrids will be evaluated in field studies to evaluate their compatibility and dry matter yield potential in a corn silage-interseeded alfalfa production system.
Objective 5. This objective will be fulfilled by conducting the following types of experiments:
1. Quantify the nutritional benefits of alfalfa and its interactions with other feed components when fed in various kinds of dairy rations and understand how protein, fiber, and other constituents in alfalfa are metabolized in the rumen and utilized for milk production vs. other less desirable outcomes such as enteric methane emissions.
2. Improve forage quality assays to more accurately predict the nutritive value of alfalfa and optimize its use in dairy rations.
Objective 6. Research will focus on incorporating plants beyond alfalfa into existing crop rotations with outcomes that incentivize farmers to adopt cover cropping practices (e.g., improved crop production as mediated by soil health, water use efficiency or provision of nutrients that is more economical than application of chemical fertilizer; increased forage availability for livestock beyond that produced by conventional cropping systems; increased provision of environmental services such as pollinator habitat, soil conservation or soil carbon storage).
Progress Report
Objective 1. Research not pursued due to SY retirement in 2018.
Objective 2. Field experiments designed to validate and test genomic prediction models for biomass/forage yield, winter survivorship, and flowering time of switchgrass were harvested as scheduled in 2020. Seven new experiments were planted and successfully established for data collection in 2021/22. Several manuscripts related to genomic prediction and selection are in preparation for submission later in FY21 and in FY22.
Objective 3.
3A. Over 8,000 red clover transplants were established in Spring 2021. Red clover transplants nurseries established in 2017, 2018, 2019, 2020, and 2021 were evaluated for plant persistence and plant biomass yield. In fall 2020 over 600 plants were selected from 2017 established nurseries and organized into over 15 polycross crossing blocks in Spring 2021. Syn 1 halfsib seed from around 1000 genotypes from over 15 polycrosses was produced during the 2020 growing season. Three Syn 2 synthetics were produced in 2020.
3B. New red clover sward trials were established in Spring 2021. Sward trials established in 2017, 2018, 2019, 2020, and 2021 were evaluated for biomass yield, persistence, plant height, maturity, and pest resistance.
3C. Alfalfa, birdsfoot trefoil, and kura clover sward trials established in 2018 and 2019 were evaluated for biomass yield, persistence, maturity, plant height, percent stand, and pest resistance. In addition, the kura clover trial was evaluated for ability to spread and spreading density. Forage quality samples were collected from the birdsfoot trefoil trial for tannin analysis. Hairy vetch, crimson clover, and Austrian Winter Pea cover crop biomass and winter survival variety trials were established in fall 2020 and evaluated through early summer 2021.
Objective 4. Five studies investigated interseeding of alfalfa into corn as a dual-purpose cover and forage crop; portions of this work were done in collaboration with the University of Wisconsin through cooperative agreement 5090-12210-001-08S. The first Wisconsin study completed in 2021 was conducted to optimize the application rate and timing of agrichemicals to enable good survival of interseeded alfalfa at the lowest possible cost to producers. A second Wisconsin study completed in 2021 examined fertilizer application strategies to help favor nutrient uptake and yield of corn grown with interseeded alfalfa. A third study completed in 2021 evaluated if alfalfa can be bred to improve its ability to survive under densely planted corn; the study was expanded by using RNA transcriptomic analysis to evaluate gene expression of good vs. poor surviving alfalfa germplasm. A fourth Wisconsin and Idaho study continued in 2021 examined how the timing of corn planting and alfalfa interseeding and corn harvest affects the yield of corn and the establishment and yield of alfalfa relative to conventional corn-alfalfa production systems. A fifth Wisconsin study that was continued and expanded in 2021 aims to identify key hybrid traits that will minimize yield drag of corn grown with interseeded alfalfa.
Objective 5. A feeding study was conducted to determine the impact of fiber digestibility of two varieties of alfalfa harvested at two different maturities on lactation performance, nutrient digestibility, rumen fermentation, and feed conversion efficiency of lactating dairy cows. Conventional and reduced-lignin alfalfa was harvested at bud and mid-flowering stage and then fed to high producing dairy cows. The feeding portion of the study was completed in the spring of 2021. Laboratory analysis of samples collected during the study has not yet started but will begin soon.
Alfalfa samples collected directly from the silo bags used in the feeding study were evaluated for neutral detergent fiber digestibility to compare in vitro methods to in vivo methods. Development of relatively fast and reliable laboratory methods to evaluate forage digestibility is needed to accurately value alfalfa in dairy cow diets. Laboratory analysis of these alfalfa samples is currently underway
Objective 6. Project planning and coordination is underway to evaluate the introduction of overwintering and value-added cover crops in dairy forage systems. Multiple studies will be implemented fall of 2021 to include a field-scale assessment of brassica cover crops alone or in combination with grass cover crops to alleviate soil compaction following an alfalfa rotation and subsequent impacts on corn silage production and two multiple-site, plot-scale evaluations of alternative and value-added cover crops/forages; pennycress will be evaluated as an overwintering cover crop and value-added oilseed meal for dairy forage rations, and silphium, which is a perennial oilseed crop and forage being developed by The Land Institute, will be tested at locations across Wisconsin to determine its optimal integration in a dairy forage rotation. These investigations are being developed with collaborators at the University of Wisconsin-Madison, The Land Institute, Cover Cress, Inc., various ARS locations, and other potential collaborators.
Accomplishments
1. Reduced ferulate cross-linking negatively impacts fitness of forage grasses. Reducing ferulate cross-linking or lignin concentration in the grass cell wall can dramatically increase digestibility of forage grasses fed to ruminant livestock. ARS researchers in Madison, Wisconsin, and St. Paul, Minnesota, developed plant materials to test the hypothesis that reductions in either ferulate cross-linking or lignin concentration had no impact on agricultural fitness of perennial grasses. This hypothesis was verified for lignin, but not for ferulate cross-linking, which had a strong and consistent negative impact on forage production, persistence, and tillering of three forage grass species. The negative impact of ferulate cross-linking was manifested as a strong reduction in stem production, severely reducing aboveground productivity and belowground production of new rhizomes and tillers. These result will guide future efforts by forage breeders to improve digestibility of forage grasses, with renewed focus on reductions in lignin concentration of both leaves and stems to avoid negative impacts on forage productivity and persistence.
2. Selection for winter survivorship increases persistence and biomass of switchgrass. Development of sustainable biomass crops requires a combination of perenniality, persistence, and high biomass production. Switchgrass is a popular candidate for sustainable biomass production, but there are no commercial switchgrass cultivars that combine all of these traits for biomass production under cold-winter climates of the northern U.S. (USDA hardiness zones 2 through 5). ARS scientists at Madison, Wisconsin, combined perenniality, persistence, and high biomass production into a single switchgrass cultivar, using plant materials collected throughout the southern U.S. followed by evaluation of thousands of plants under severe winter conditions. This research demonstrated that selection of surviving plants following harsh winter conditions led to heritable and consistent improvements in several switchgrass populations collected from different regions. In some populations, the genetic gains were sufficient to create northern-adapted populations with 50-70% increased biomass production over traditional local cultivars and nearly 100% survival over three winters. This research has led to the development of one new switchgrass cultivar scheduled for public release and dissemination to stakeholders for sustainable biomass production and continued agronomic and physiological research.
3. Plot type has a dramatic impact on switchgrass cultivar ranking and performance. Biomass production of switchgrass, on a commercial scale, will take place from broadcast or drill seedings in which seedlings must survive a 1- to 2-year establishment phase. Due to pressures to obtain rapid research results, many researchers cut corners in evaluating switchgrass cultivars and breeding lines, using various plant spacings that completely eliminate interplant competition and opportunities for the most vigorous and most fit seedlings to express themselves. ARS researchers at Madison, Wisconsin, evaluated nine cultivars under five different plant spacings, two of which involved direct interplant competition among seedlings. Correlations between the two seeded plot types, both with competition, were high, but neither of these plot types were highly correlated with the three plot types that did not include any interplant competition. In general, the wider the plant spacing, the lower the correlation with the seeded plot types. DNA markers revealed numerous chromosome regions that were significantly altered across three time points that represented original seed, seedlings surviving four months of interplant competition, and adult plants surviving one year of interplant competition. Thus, there appears to be some basis for genetic selection occurring during interplant competition of the establishment phase for switchgrass biomass plantings. Some form of interplant competition during establishment appears to be essential for expression of maximum performance of switchgrass cultivars. Without this competition, performance rankings of switchgrass cultivars are highly unreliable, providing guidance to agronomists and plant breeders that switchgrass must be evaluated under realistic sward conditions to be relevant to production environments.
Review Publications
Grabber, J.H., Osterholz, W.R., Riday, H., Cassida, K.A., Williamson, J.A., Renz, M.J. 2021. Differential survival of alfalfa varieties interseeded into corn silage. Crop Science. 61(3): 1797-1808. https://doi.org/10.1002/csc2.20465.
Osterholz, W.R., Renz, M.J., Grabber, J.H. 2020. Alfalfa establishment by interseeding with silage corn projected to increase profitability of corn silage-alfalfa rotations. Agronomy Journal. 112(5):4120-4132. https://doi.org/10.1002/agj2.20312.
Osterholz, W.R., Dias, J.L.C.S., Grabber, J.H., Renz, M.J. 2020. Pre- and post-applied herbicides options for alfalfa interseeded with corn silage. Weed Technology. 35(2):263-270. https://doi.org/10.1017/wet.2020.104.
Santa-Martinez, E., Castro, C.C., Flick, A.J., Sullivan, M.L., Riday, H., Clayton, M.K., Brunet, J. 2021. Bee species visiting Medicago sativa differ in pollen deposition curves with consequences for gene flow. American Journal of Botany. 108(6):1016-1028. https://doi.org/10.1002/ajb2.1683.
Kucek, L.K., Azevedo, M.D., Eagen, S., Ehlke, N., Hayes, R.J., Mirsky, S.B., Reberg-Horton, C., Ryan, M.R., Wayman, S., Wiering, N.P., Riday, H. 2021. Seed dormancy regulated by genotype and environment in Hairy vetch (Vicia villosa Roth). Agronomy Journal. 10(11). Article 1804. https://doi.org/10.3390/agronomy10111804.
