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

2020 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
Subobjective 1A. We made substantial progress on developing procedures and quantifying soil health attributes and their impact on agronomic production. We began to take monthly samples starting in September 2019 to better understand the dynamic flow of carbon and nutrients in these systems. To date, we have collected and analyzed 270 soil samples from the treatments since October 1, 2019. We also implemented a mixed species vs. single species cover crop trial under both conventional till and no-till systems in Field 1 (50 ha). The mixed species vs single species showed a significant increase in microbial activity and carbon availability vs the single species across both tillage systems. For Field 2 (20 ha) preliminary results from monthly sampling reveal a much more dynamic system than we realized based on soil microbial activity, water extractable carbon and nitrogen availability and nutrient availability. The data suggests that in Blackland Prairie soils, tillage does not alter the soil health score vs. no-till. We recorded no significant differences in the soil health scores when comparing conventional-till vs no-till using mixed species cover crops. It seems that soils that are self-mulching (high clay Vertisols) can see increasing soil health scores at the same rate as not tilling the soil when cover crops are used to prime the soil microbial community. Subobjective 1B. We completed the first year of sampling and analysis of the effects of conventional and conservation tillage on soil fertility, greenhouse gas emissions, soil microbial diversity, yield, grain, fiber quality, and fertilizer use efficiency (nitrogen and phosphorus). Yield maps generated for tillage treatments including conventional till, and a 3-year corn/corn/cotton rotation that incorporates strip till (ST), no-till (NT), precision fertilizer placement and cover crops. Yield maps showed no differences among corn yield response among tillage regimes, where cotton yield increased using strip tillage. Soil and plant samples were collected to document the nitrogen and phosphorus uptake efficiency in each treatment. We evaluated the effect of tillage and fertilizer placement on nitrous oxide emissions. No-tillage and banding fertilizer produced less nitrous oxide emissions than conventional tillage and placement of fertilizer. Nitrous oxide emissions were greater for surface applied fertilizer than banded and were higher following rain events. Nitrous oxide emissions factors from conventional till accounted for greater than 2% of fertilizer nitrogen, where no-till treatments were below 1%. The treatments will continue in successive years. Subobjective 2A. We continued to document the long-term effects of precipitation variation on biomass yield in 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. Stand level harvest was accompanied by harvests of 1 meter x 1 meter area plots to determine meter-scale biomass productivity and plant species composition. The stand level harvest yields estimates of biomass productivity on a scale relevant to producers while the plot scale harvest is a standard approach in basic ecological studies and will allow us to relate the stand harvests to the broader literature when the study is complete in 2022. This subobjective is part of our Long-Term Agroecosystem Research (LTAR) research. Subobjective 2B. Improving inter-annual stability (reliability) in biomass production systems is critical to the economic viability of producers. Questions remain as to the number and properties of plant species that should be included in grassland communities in order to maximize temporal stability. We used 4 growing seasons of remote measurements of canopy reflectance to calculate aboveground productivity and a leaf property previously identified to influence stability [leaf dry matter content (LDMC); leaf wet weight/leaf dry weight] for grassland planted as a species mixture or monoculture of a tallgrass species (switchgrass). Canopy reflectance of sunlight was measured at approximately 2-week intervals during each growing season in 104, 7 meter diameter patches in each of the two vegetation types. We developed regression relationships between reflectance and two variables, grassland biomass and LDMC. Regressions were used to calculate annual productivity and LDMC values for patches of each vegetation type from measurements of reflectance. Ultimately, we will use calculated values of productivity and LDMC to determine inter-annual stability in productivity and assess effects of among-year variation in community LDMC vs variation in productivity-LDMC relationships on stability. Subobjective 2C. Plant community composition manipulations that were begun in 2019 were successfully established during 2020 in switchgrass stands. Dominant grass species were selectively removed by hand-applying glyphosate to individual plants without collateral damage to non-targeted species, a technique we have long applied in several past field experiments. We anticipate the removal treatments can be maintained with minor additional effort in the remaining years of the experiment. The second year of water and nitrogen additions were conducted, and analysis of first year responses to species manipulations and water/nitrogen additions are in progress. We completed analyses of the nitrogen content and partitioning of soil and plant tissues collected during the 2019 season, and these data will indicate the sources and nitrogen transformations in switchgrass stands. Subobjective 3A. Bare (exposed) soil influences several ecosystem processes on grazing lands but is a challenge to quantify frequently and over large areas. We developed an algorithm to use low-altitude measurements of the reflectance of sunlight to quantify fractional aerial coverage of bare soil (bare fraction) on grazing lands. The method has been validated for and is being applied to reflectance data collected for two ecosystems, semi-arid shortgrass steppe and mesic grassland, each subject to different grazing treatments. We plan to use geospatial statistical tools to test predictions about the influence of grazing treatment on the amount and spatial patterning of bare soil. Subobjective 3B. One scientist and a database manager were hired to support Long-Term Agroecosystem Research (LTAR) efforts. These personnel have improved Texas Gulf site integration into the greater LTAR network. Business as Usual and Aspiration grazing management treatments continued through fiscal year 2020. The Riesel watersheds were in a drought at the start of fiscal year 2020, which continued until late winter. Winter supplemental grazing (oat) for the Business as Usual treatment had good germination and provided ample grazing. The Aspiration treatment winter grazing (Austrian winter pea, oat and vetch) germinated late and provided less vegetation than the other grazing treatment. The summer grazing crop (millet, cow peas, safflower and sorghum) for the Aspirational treatment also suffered from poor germination and may not provide ample supplemental grazing during the summer. Fortunately, a wet early spring provided enough hay that can be used to supplement forage needs if needed.

Accomplishments
1. How best to measure global patterns in grassland nitrogen availability. The availability of nitrogen in ecosystems often determines their ability to provide ecosystem services critical to human well-being, the integrity of wild and agricultural ecosystems, and climate regulation, such as food and fiber, hydrologic regulation, and carbon sequestration. The availability of nitrogen needed in ecosystem processes is strongly affected by climate, soils, and biological properties of ecosystems, and therefore will be strongly influenced by human activities. Understanding the controls on nitrogen availability on a world-wide basis is crucial for understanding the effects of human activities on nitrogen availability, mitigating deleterious effects, and maintaining beneficial ones. Current understanding is based on laboratory measurements of nitrogen availability, which may not accurately represent actual availability. ARS researchers at Temple, Texas, collaborated with an international team of scientists to compare laboratory and field measurements of nitrogen availability in soils from 30 grasslands spread across six continents. The study found that while laboratory measurements of soil nitrogen availability poorly predicted field nitrogen availability in these grasslands, laboratory measurements could make good predictions of field nitrogen availability by accounting for soil properties and climate. This finding is an important step toward a better understanding of the processes in ecosystems that maintain healthy wild and agricultural ecosystems.

2. Switchgrass genes help plants thrive in some places and not in others. ARS researchers at Temple, Texas, together with university collaborators tested for specific genes (‘loci’) that underlie adaptation to the environment (‘local adaptation’) in switchgrass, an emerging biofuel crop and dominant tallgrass species. Switchgrass genes help plants thrive in some places and not in others. Finding the specific genes that adapt plants to their environments is both a central goal of plant biology and critical to breeding improved crops for agricultural production. The study assessed genetic variation across at 10 locations spread across a large regional gradient in the range of switchgrass from Texas to South Dakota. This is one of the largest studies to date of genetic controls of plant adaptation to the environment. The study identified loci related to biomass yield and found that that most loci contributed to local adaptation at some sites but were neutral in their contribution to adaptation at others. Few loci caused negative effects. By identifying genetic loci related to biomass yield across a large portion of the range of switchgrass, these results will inform breeding of new locally adapted varieties of switchgrass.

3. Plant traits regulate spatial and temporal variation in productivity. Inter-annual stability in plant productivity is influenced by several properties of plant communities. However, the properties that most strongly regulate stability remain in question. ARS researchers at Temple, Texas assessed effects of two properties of multi-species plant communities on inter-annual stability in aboveground productivity of restored grassland. Properties included two components related to species composition (species diversity of local communities and dissimilarity in composition between local communities) and two functional attributes (mean aboveground biomass and a community leaf trait; leaf dry matter content). Combined, the productivity of different communities varied less among years when community differences in biomass and leaf dry matter were large than small. Communities that differed in these functional attributes differed in their productivity responses to precipitation variation. Differing productivity responses, in turn, stabilized the overall productivity of communities combined. By contrast, species diversity and dissimilarity between communities had relatively little effect on stability in productivity. Our results indicate that inter-annual stability in grassland productivity was determined by community differences in functional attributes that link plant growth to precipitation variation.

4. Intercropping switchgrass with hybrid poplar increased carbon sequestration on a sand soil. ARS researchers at Temple, Texas, studied a switchgrass/hybrid poplar intercropping system to develop a soil carbon inventory to evaluate whether this intercrop system could increase carbon sequestration on a sand soil compared to either species grown in monoculture. Switchgrass has been identified as an important source of cellulosic biomass to produce biofuels and has been shown to improve soil carbon cycling. Four years of intercropping resulted in a 17% increase in soil organic carbon in the soil surface compared to the monoculture of poplars and an increase in the amount and age of stabilized carbon. The study further showed the potential for switchgrass to be a viable energy crop, generating essential information for biofuel producers to adjust energy production goals and possibly develop secondary markets such as carbon credit trading.

Review Publications
Hills, K., Collins, H.P., Yorgey, G., McGuire, A., Kruger, C. 2020. Improving soil health in pacific northwest potato production: A review. American Journal of Potato Research. 97:1-22. https://doi.org/10.1007/s12230-019-09742-7.
Polley, H.W., Yang, C., Wilsey, B.J., Fay, P.A. 2020. Spectrally derived values of community leaf dry matter content link shifts in grassland composition with change in biomass production. Remote Sensing in Ecology and Conservation. 6(3):344-353. https://doi.org/10.1002/rse2.145.
Khan, A.R., Reichmann, L.G., Ibal, J.C., Shin, J.H., Liu, Y., Collins, H.P., LePage, B., Terry, N. 2019. Variation in pickleweed root-associated microbial communities at different locations of a saline solid waste management unit contaminated with petroleum hydrocarbons. PLoS One. 14(10):e0222901. https://doi.org/10.1371/journal.pone.0222901.
Ramphisa, P., Collins, H.P., Bair, E.K., Davenport, J. 2019. Corn biomass, uptake and fractionation of soil phosphorus in five soils amended with organic wastes as P fertilizers. Journal of Plant Nutrition. 43(3):335-353. https://doi.org/10.1080/01904167.2019.1683194.
Risch, A.C., Zimmermann, S., Ochoa-Hueso, R., Schütz, M., Frey, B., Firn, J.L., Fay, P.A., Hagedorn, F., Borer, E.T., Seabloom, E.W., Harpole, W.S., Knops, J.M.H., McCulley, R.L., Broadbent, A.A.D., Stevens, C.J., Silveira, M.L., Adler, P.B., Báez, S., Biederman, L.A., Blair, J.M., Brown, C.S., Caldeira, M.C., Collins, S.L., Daleo, P., di Virgilio, A., Ebeling, A., Eisenhauer, N., Esch, E., Eskelinen, A., Hagenah, N., Hautier, Y., Kirkman, K.P., MacDougall, A.S., Moore, J.L., Power, S.A., Prober, S.M., Roscher, C., Sankaran, M., Siebert, J., Speziale, K.L., Tognetti, P.M., Virtanen, R., Yahdjian, L., Moser, B. 2019. Soil net nitrogen mineralisation across global grasslands. Nature Communications. 10(4981):1-10. https://doi.org/10.1038/s41467-019-12948-2.
Upton, R.N., Sielaff, A.C., Hofmockel, K.S., Xu, X., Polley, H.W., Wilsey, B.J. 2020. Soil depth and grassland origin cooperatively shape microbial community co-occurrence and function. Ecosphere. 11(1):e02973. https://doi.org/10.1002/ecs2.2973.
Smith, D.R., Macrae, M., Kleinman, P.J., Jarvie, H.P., King, K.W., Bryant, R.B. 2019. The latitudes, attitudes, and platitudes of watershed phosphorus management in North America. Journal of Environmental Quality. 48(5):1176-1190. https://doi.org/10.2134/jeq2019.03.0136.
Lohani, S., Baffaut, C., Thompson, A.L., Aryal, N., Bingner, R.L., Bjorneberg, D.L., Bosch, D.D., Bryant, R.B., Buda, A.R., Dabney, S.M., Davis, A.R., Duriancik, L.F., James, D.E., King, K.W., Kleinman, P.J., Locke, M.A., McCarty, G.W., Pease, L.A., Reba, M.L., Smith, D.R., Tomer, M.D., Veith, T.L., Williams, M.R., Yasarer, L.M. 2020. Performance of the Soil Vulnerability Index with respect to slope, digital elevation model resolution, and hydrologic soil group. Journal of Soil and Water Conservation. 75(1):12-27. https://doi.org/10.2489/jswc.75.1.12.
Lowry, D.B., Lovell, J.T., Zhang, L., Bonnette, J., Fay, P.A., Mitchell, R., Lloyd-Reilley, J., Boe, A.R., Wu, Y., Rouquette, F.M., Wynia, R.L., Weng, X., Behrman, K.D., Healey, A., Barry, K., Lipzen, A., Bauer, D., Sharma, A., Jenkins, J., Schmutz, J., Fritschi, F.B., Juenger, T.E. 2019. QTL x environment interactions underlie adaptive divergence in switchgrass across a large latitudinal gradient. Proceedings of the National Academy of Sciences. 116(26):12933-12941. https://doi.org/10.1073/pnas.1821543116.
Wang, S., Adhikari, K., Zhuang, Q., Yang, Z., Jin, X., Wang, Q., Bian, Z. 2020. An improved similarity-based approach to predicting and mapping soil organic carbon and soil total nitrogen in a coastal region of northeastern China. PeerJ. 8:e9126. https://doi.org/10.7717/peerj.9126.
Mndowla, E., Collins, H.P., Miklas, P.N. 2018. Plant growth response of eight andean dry bean (Phaseolus vulgaris L.) genotypes to phosphorus fertilizer in the greenhouse. Agricultural Sciences. 9(10):1269-1285. https://doi.org/10.4236/as.2018.910089.
Firn, J., McGree, J., Harvey, E., Flores-Moreno, H., Schütz, M., Buckley, Y.M., Borer, E., Seabloom, E., La Pierre, K.J., MacDougall, A.M., Prober, S.M., Stevens, C.J., Sullivan, L., Porter, E., Ladouceur, E., Allen, C., Moromizato, K.H., Morgan, J.W., Harpole, W.S., Hautier, Y., Eisenhauer, N., Wright, J., Adler, P.B., Arnillas, C.A., Bakker, J.D., Biederman, L., Broadbent, A.A., Brown, C.S., Bugalho, M.N., Caldeira, M., Cleland, E., Ebeling, A., Fay, P.A., Hagenah, N., Kleinhesselink, A.R., Mitchell, R., Moore, J.L., Nogueira, C., Peri, P.L., Roscher, C., Smith, M., Wragg, P.D., Risch, A.C. 2019. Leaf nutrients, not specific leaf area, are consistent indicators of elevated nutrient inputs. Nature Ecology and Evolution. 3:400-406. https://doi.org/10.1038/s41559-018-0790-1.
Smith, D.R., Jarvie, H.P., Harmel, R.D., Haney, R.L. 2019. The role of field-scale management on soil and surface runoff C/N/P stoichiometry. Journal of Environmental Quality. 48(5):1543-1548. https://doi.org/10.2134/jeq2018.09.0338.
Penn, C.J., Gonzalez, J.M., Williams, M.R., Smith, D.R., Livingston, S.J. 2019. The past, present, and future of blind inlets as a surface water best management practice. Critical Reviews in Environmental Science Technology. 50(7):743-768. https://doi.org/10.1080/10643389.2019.1642836.
Gilbert, B., MacDougall, A.S., Kadoya, T., Akasaka, M., Bennett, J.R., Lind, E.M., Flores-Moreno, H., Firn, J., Hautier, Y., Borer, E.T., Seabloom, E.W., Adler, P.B., Cleland, E.E., Grace, J.B., Harpole, W.S., Esch, E.H., Moore, J.L., Knops, J., McCulley, R., Mortensen, B., Bakker, J., Fay, P.A. 2020. Climate and local environment structure asynchrony and the stability of primary production in grasslands. Global Ecology and Biogeorgraphy. 29(7):1177-1188. https://doi.org/10.1111/geb.13094.
Collins, H.P., Kimura, E., Polley, H.W., Fay, P.A., Fransen, S. 2020. Intercropping switchgrass with hybrid poplar increased carbon sequestration on a sand soil. Biomass and Bioenergy. 138:105558. https://doi.org/10.1016/j.biombioe.2020.105558.
Polley, H.W., Yang, C., Wilsey, B.J., Fay, P.A. 2020. Temporal stability of grassland metacommunities is regulated more by community functional traits than species diversity. Ecosphere. 11(7):e03178. https://doi.org/10.1002/ecs2.3178.
Wilsey, B., Xu, X., Polley, H.W., Hofmockel, K., Hall, S.J. 2020. Lower soil carbon stocks in exotic vs. native grasslands are driven by carbonate losses. Ecology. 101(7):e03039. https://doi.org/10.1002/ecy.3039.