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

Objectives
Objective 1: Develop procedures and quantify soil health attributes and their impact on agronomic production. Subobjective 1A: Determine the seasonal changes in inherent soil carbon and nutrient cycling potentials (N and P) using the Soil Health Nutrient Tool under conventional and no-till with two different crop rotation systems incorporating legume-dominated cover crops. Subobjective 1B: Determine the effects of conventional and conservation tillage (strip till, no-till) on soil fertility, greenhouse gas emissions, soil microbial diversity, yield, grain, fiber quality, and fertilizer use efficiency (N and P) which contribute to soil health attributes. Objective 2: Quantify native and managed grassland response to biological and climate variability. Subobjective 2A: Document long-term effects of precipitation variation on trends in biomass yield and ecosystem services from grasslands of different species composition. Subobjective 2B: Assess the linkage between the weighted values of Leaf Dry Matter Content of grassland communities and temporal variability in aboveground productivity. Subobjective 2C: Manipulate grassland community composition and resource availability to test the contributions of plant species and functional traits to grassland productivity. Objective 3: Operate and maintain the Texas Gulf Coast LTAR network site using technologies and practices agreed upon by the LTAR leadership. Contribute to the LTAR working groups and common experiments as resources allow. Submit relevant data with appropriate metadata to the LTAR Information Ecosystem. Subobjective 3A: Implement the Texas Gulf Coast LTAR Common Experiment comparing the sustainability of traditional grazing systems and adaptively managed rotational grazing systems. Subobjective 3B: Develop and enhance infrastructure for data acquisition, storage, and transfer to meet LTAR and REE data acquisition and archiving standards.

Approach
Research will apply a Genetics x Environment x Management approach quantify nutrient losses from fertilizer, interannual variability in biomass production, and grazing impacts on traditionally managed agroecosystems common in the southern U.S. Great Plains and evaluate results from management actions designed to reduce negative impacts of fertilization, precipitation variability, and grazing.

Progress Report
Sub-objective 1B. We continued to evaluate the effect of tillage on greenhouse gas emissions in a corn/corn/cotton rotation under conventional till, strip till and no-till. Soil samples have been analyzed for microbial diversity and activity using Phospholipid Fatty Acid analysis for crop years 2020 and 2021 from each field. Soil, and plant tissues of corn and cotton are being analyzed for nitrogen and phosphorous uptake and use efficiency. Sub-objective 2A. We continued building the long-term record of year-to-year variability in biomass production from 8 native grassland and 16 switchgrass stands. The stands are approximately 1 acre in area and were harvested with commercial haying equipment and hay bales were weighed and sampled for moisture, carbon, and nitrogen contents. The 2020 harvest represents the 11th year of the study, and this research contributes to our Long-Term Agroecosystem Research program. Switchgrass stands continue to out-yield adjacent high-diversity restored grassland. Harvest subsamples from the two soil types traversed by these stands were not collected in 2020 because of pandemic-related limitations. We made substantial progress measuring soil carbon and nitrogen pools from soil cores collected in 2016 from these stands because we successfully recruited a new technician who is focusing on this task. We anticipate completion of soil core analysis by end of 2021. Sub-objective 2B. We advanced our ability to predict stability in biomass production in the native grassland and switchgrass stands. We applied multispectral remote sensing from unmanned aerial vehicle (UAV) platforms to identify community scale values of a leaf trait, leaf dry matter content (LDMC). We predicted that year-to-year change in biomass production (‘stability’) would decline as year-to-year variability in community scale LDMC and its relationship to annual biomass production increased. We found that stability was regulated by different components of the LDMC effect on aboveground net primary productivity in native grassland and switchgrass stands. In native grassland, stability depended mainly on year-to-year variation in community LDMC. Conversely, stability in switchgrass depended primarily on year-to-year variation in the biomass-LDMC relationship. This project provides the launching point for research that will be conducted in pursuit of a Master of Science degree by the ARS technician supporting this project. The aim will be improved ability to identify plant species composition using remote sensing instruments on UAVs. Sub-objective 2C. Plant community composition manipulations that were established in 2020 were continued in 2021 in switchgrass stands. The multi-year treatment selectively removing switchgrass or several common exotic invasive grasses is fully established, and the preliminary analyses indicate that switchgrass is competitively dominant to the invasive grasses, especially when water and nitrogen fertilizer are added. In the 2021 field season we are collecting data on mechanisms potentially conferring competitive superiority on switchgrass, including leaf and plant physiological and morphological traits and soil carbon dioxide efflux. The results in hand are robust, and we plan to conclude this experiment with aboveground biomass harvest in fall 2021. Objective 3. We made numerous contributions to Long-Term Agroecosystem Research (LTAR) working groups and datasets. Scientists on this project are contributing biomass yield and site weather data to an online data repository and are co-authoring manuscripts on agroecosystem water use efficiency by the Water Use Efficiency Working Group, developing biodiversity metrics for crop and rangeland systems in the Biology Working Group, and developing a special issue for Journal of Environmental Quality by the Manureshed Working Group. Sub-objective 3A. We developed a technique for rapid spectral measurements of live vegetation cover at small spatial scale using an unmanned aerial vehicle (UAV) platform. We then applied the technique to determine effects of grazing treatments on live vegetation cover in shortgrass prairie pastures in northeastern Colorado and improved pasture in central Texas. Heavy grazing in the shortgrass and rotational grazing in improved pasture increased spatial uniformity in live vegetation cover compared to other grazing treatments. The technique shows promise for evaluating grazing impacts in native and improved pastures. We expanded our remote sensing studies of agroecosystems by beginning analysis of Sentinel-2 MSI satellite data to determine the most sensitive vegetation index for the various crop management practices. Sub-objective 3B. LTAR monitoring continued at Riesel. Soil, air, and water quality analysis were completed throughout the year, as was productivity data. Analysis of white space was evaluated as a means to move large amounts of data, for example sub-hourly meteorological data. ARS researchers are collaborating with USDA Natural Resources Conservation Service to develop a Conservation Plan for the Riesel Watersheds.

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.