Research Project: Contributions of Climate, Soils, Species Diversity, and Management to Sustainable Crop, Grassland, and Livestock Production Systems

Location: Grassland Soil and Water Research Laboratory

2021 Annual Report

Accomplishments
1. Complex feedbacks control grassland soil carbon dioxide losses under CO2 enrichment. The effects of atmospheric carbon dioxide (CO2) enrichment on grasslands depend strongly on how much CO2 is subsequently lost back to the atmosphere through the process known as ‘soil respiration’. This loss can represent a sizeable amount of the carbon gained by ecosystems through photosynthesis, so understanding the controls on this loss is critical to understanding how much carbon is stored by ecosystems, where it cannot contribute to climate warming. In a long-term study of the carbon gains and losses in grasslands in Central Texas, ARS researchers found that the increase in grassland productivity with CO2 enrichment was the most consistent predictor of the amount of loss, but that at elevated CO2 levels productivity continued to increase at a faster rate than did losses to soil respiration. This implies increased storage of carbon in this grassland at future elevated CO2 concentrations, although there was also evidence for considerable variation among coarse and fine textured soils. The causes of buildups or losses of carbon in grasslands is critical information for land managers and policy makers, enabling management decisions and policies that will improve the sustainability of grasslands managed for agricultural production and other ecosystem goods and services.

2. Multiple genetic pathways to climate adaptation in the biofuel crop, Switchgrass. Switchgrass is a perennial grass undergoing development as a candidate for biomass production in support of an emerging bioenergy and bioproducts industry. The genetics of switchgrass are complex, so knowledge of the organization of its genome and its evolutionary history are critical to support development of new adapted varieties to optimize biomass production across the broad geographic range of switchgrass. ARS researchers and collaborators developed a comprehensive DNA sequence of the entire switchgrass genome, combined with a comprehensive analysis of its evolutionary history. This analysis revealed three distinct switchgrass populations: Gulf Coast, Atlantic, and Midwest. These populations form distinct gene pools that form a basis for breeding and selection to develop varieties suitable for use in diverse agricultural systems and environments. These results represent a huge step forward in understanding the genetic structure of this candidate bioenergy crop and the evolution of one of the most widespread and abundant native perennial grasses in North America. More broadly, the complete switchgrass genome will open new avenues through which native grasses can benefit agriculture and conservation.

3. Traits matter more than species in stability of biomass production. One goal of bioenergy research is to identify grassland systems in which production is temporally stable, where stability is defined as the ratio of mean biomass production to inter-annual variation in production. Questions remain as to the number and types of plant species that should be included in grassland communities to maximize temporal stability. Two schools of thought predominate. One view posits that stability is increased by increasing species number. A second view holds that stability depends primarily on leaf and other properties of species in the community. We measured temporal stability in aboveground biomass production in 104, 7-m patches each of a species-rich mixture of native perennial grass and forb species and monoculture of switchgrass in central Texas, U.S. For communities of both vegetation types, we measured the average value of a leaf property previously identified to influence stability (leaf dry matter content; leaf wet weight/leaf dry weight). We found that production varied among years in response to inter-annual variation (IAV) in precipitation. The precipitation effect on stability was expressed through IAV in both the community-averaged value of leaf dry matter content and the relationship between production and leaf dry matter content. Temporal stability over 4 years was similar between vegetation types but was regulated by different components of the leaf dry matter content effect on production in species mixture and switchgrass. Our results support the view that stability in biomass production depends more on leaf properties of the species present in a plant community than species number. Similar levels of stability can be achieved among communities despite differences in the primary pathway via which leaf traits influence production.

4. Livestock manure may improve agroecosystem sustainability. Managing manures is one of the most difficult subjects in modern agriculture, touching upon issues of resource management, human and environmental health, and crop production. USDA’s Long-Term Agroecosystem Research (LTAR) Network is using the concept of a "manureshed” to develop a vision for reintegrating the nation’s livestock and crop production systems. By optimizing the distribution of livestock manure to croplands and pasturelands in need of nutrients, this research demonstrates the potential for improved manure use to improve the sustainability of crop and livestock production well into the future.

5. Residue management changed soil phosphorus availability in a wheat-fallow rotation in the Pacific Northwest. Crop residue management strategies have exhibited significant effects on crop growth and soil properties, which in turn may influence soil phosphorus (P) transformation and availability. The effect of long-term (83-year) crop residue management treatments on soil P availability and storage capacity in the surface (0–0.3 m) and subsurface (0.3–0.6 m) were investigated relative to straw incorporated into soil (control) in a wheat-fallow rotation in the Pacific Northwest. Nitrogen application significantly decreased soil available P due to P removal by the wheat crop. Straw burning had no significant effect on soil P balance but decreased available P due to the loss of organic carbon. Manure application significantly increased soil available P in surface soil. An understanding of the transformation and availability of P in soils under different residue management will lead to a better assessment and development of fertilizer management strategies.

Review Publications
Lamichhane, S., Kumar, L., Adhikari, K. 2021. Updating the national soil map of Nepal through digital soil mapping. Geoderma. 394. Article 115041. https://doi.org/10.1016/j.geoderma.2021.115041.
Baath, G.S., Flynn, K.C., Gowda, P.H., Kakani, V.G., Northup, B.K. 2021. Detecting biophysical characteristics and nitrogen status of finger millet at hyperspectral and multispectral resolutions. Frontiers in Agronomy. 2. Article 604598. https://doi.org/10.3389/fagro.2020.604598.
Adhikari, K., Smith, D.R., Collins, H.P., Haney, R.L., Wolfe, J. 2021. Corn response to selected soil health indicators in a Texas drought. Ecological Indicators. 125. Article 107482. https://doi.org/10.1016/j.ecolind.2021.107482.
Yan, Z., Collins, H.P., Machado, S., Long, D.S. 2021. Residue management changes soil phosphorus availability in a long-term wheat-fallow rotation in the Pacific Northwest. Nutrient Cycling in Agroecosystems. 120(1):69-81. https://doi.org/10.1007/s10705-021-10136-7.
Wang, S., Loreau, M., de Mazancourt, C., Isbell, F., Beierkuhnlein, C., Connolly, J., Deutschman, D.H., Dolezal, J., Eisenhauer, N., Hector, A., Jentsch, A., Kreyling, J., Lanta, V., Leps, J., Polley, H.W., Reich, P.B., van Ruijven, J., Schmid, B., Tilman, D., Wilsey, B., Craven, D. 2021. Biotic homogenization destabilizes ecosystem functioning by decreasing spatial asynchrony. Ecology. 102(6). Article e03332. https://doi.org/10.1002/ecy.3332.
Collins, H.P., Kimura, E., Smith, D.R. 2020. Sweet corn phosphorus uptake from sandy soil amended with anaerobically-digested manure. Communications in Soil Science and Plant Analysis. 51(18):2398-2413. https://doi.org/10.1080/00103624.2020.1836208.
Polley, H.W., Collins, H.P., Fay, P.A. 2020. Biomass production and temporal stability are similar in switchgrass monoculture and diverse grassland. Biomass and Bioenergy. 142. Article 105758. https://doi.org/10.1016/j.biombioe.2020.105758.
Fay, P.A., Hui, D., Jackson, R.B., Collins, H.P., Reichmann, L.G., Aspinwall, M.J., Jin, V.L., Khasanova, A.R., Heckman, R.W., Polley, H.W. 2021. Multiple constraints cause positive and negative feedbacks limiting grassland soil CO2 efflux under CO2 enrichment. Proceedings of the National Academy of Sciences(PNAS). 118(2). Article e2008284117. https://doi.org/10.1073/pnas.2008284117.
VanWallendael, A., Bonnete, J., Juenger, T.E., Fritschi, F.B., Fay, P.A., Mitchell, R.B., Lloyd-Reilley, J., Rouquette Jr., F.M., Bergstrom, G.C., Lowry, D.B. 2020. Geographic variation in the genetic basis of resistance to leaf rust between locally adapted ecotypes of the biofuel crop switchgrass (Panicum virgatum). New Phytologist. 227(6):1696-1708. https://doi.org/10.1111/nph.16555.
Heckman, R.W., Khasanova, A.R., Johnson, N.S., Weber, S., Bonnette, J.E., Aspinwall, M.J., Reichmann, L.G., Juenger, T.E., Fay, P.A., Hawkes, C.V. 2020. Plant biomass, not plant economics traits, determines responses of soil CO2 efflux to precipitation in the C4 grass Panicum virgatum. Journal of Ecology. 108:2095-2106. https://doi.org/10.1111/1365-2745.13382.
Lovell, J.T., MacQueen, A.H., Mamidi, S., Bonnette, J., Jenkins, J., Napier, J.D., Sreedasyam, A., Healey, A., Session, A., Shu, S., Barry, K., Bonos, S., Boston, L., Daum, C., Deshpande, S., Ewing, A., Grabowski, P., Haque, T., Harrison, M.L., Jiang, J., Kudrna, D., Lipzen, A., Pendergast IV, T.H., Plott, C., Qi, P., Saski, C.A., Shakirov, E., Sims, D., Sharma, M., Sharma, R., Stewart, A., Singan, V., Tang, Y., Thibivillier, S., Webber, J., Weng, X., Williams, M., Wu, A., Yoshinaga, Y., Zane, M., Zhang, L., Zhang, J., Behrman, K.D., Boe, A.R., Fay, P.A., Fritschi, F.B., Jastro, J.D., Lloyd-Reilley, J., Martinez-Reyna, J., Matamala, R., Mitchell, R., Rouquette Jr., F.M., Ronald, P., Saha, M., Tobias, C.M., Udvardi, M., Wing, R., Wu, Y., Bartley, L.E., Casler, M.D., Devos, K.M., Lowry, D.B., Rokhsar, D., Grimwood, J., Juenger, T.E., Schmutz, J. 2021. Genomic mechanisms of climate adaptation in polyploid bioenergy switchgrass. Nature Genetics. 590:438-444. https://doi.org/10.1038/s41586-020-03127-1.
Bos, J.H., Williams, M.R., Smith, D.R., Armstrong, S., Harmel, R.D. 2021. Long-term effect of poultry litter application on phosphorus balances and runoff losses. Journal of Environmental Quality. 50(3):639-652. https://doi.org/10.1002/jeq2.20219.
Zhang, X., Lopes, I., Ni, J., Yuan, Y., Huang, C., Smith, D.R., Chaubey, I., Wu, S. 2021. Long-term performance of three mesophilic anaerobic digesters to convert animal and agro-industrial wastes into organic fertilizer. Journal of Cleaner Production. 307. Article 127271. https://doi.org/10.1016/j.jclepro.2021.127271.
Macrae, M., Jarvie, H., Brouwer, R., Gunn, G., Reid, K., Joosse, P., King, K.W., Kleinman, P.J., Smith, D.R., Williams, M.R., Zwonitzer, M. 2021. One size does not fit all: towards regional conservation practice guidance to reduce phosphorus loss risk in the Lake Erie watershed. Journal of Environmental Quality. 50(3):529-546. https://doi.org/10.1002/jeq2.20218.
Admas, S., Haileselassie, T., Tesfaye, K., Shiferaw, E., Flynn, K.C. 2021. Evaluation of Ethiopian chickpea (Cicer arietinum L.) genotypes for frost tolerance. Acta Agriculturae Slovenica. 117(2):1-14. https://doi.org/10.14720/aas.2021.117.2.2079.