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2019 Annual Report
Objectives
Objective 1: Develop management practices incorporating the latest technology developments for a field size aspirational four year, dryland crop rotation system with precision nutrient, agrichemical, weed control and crop population management.
Sub-objective 1a. Identify and quantify production parameters most important in affecting economic yields across a dryland field-scape.
Sub-objective 1b. Develop methods for quantifying optimal precision N management for specific management zones in wheat-based dryland rotation.
Sub-objective 1c. Develop methods to quantify optimal corn populations for specific management zones in a four-year aspirational rotation.
Sub-objective 1d. Develop and evaluate new tools for assessing soil quality across a field-scape using spectral scanning (FTIR) and other quick methods.
Sub-objective 1e. Evaluate the use of drone based data for the quantification of crop water stress in dryland crop rotations.
Objective 2: Compare yields, economic returns, and environmental impacts of the aspirational rotation system, to a dryland rotation system currently used by producers of the region.
Sub-objective 2a. Quantify and compare grain yields and economic returns from a precision-managed four-year aspirational no-till rotation with a “business as usual” reduced-till wheat-fallow rotation.
Sub-objective 2b. Quantify and evaluate changes in soil quality as affected by both management systems across the field-scape.
Objective 3: Evaluate potential alternative crops and management practices for introduction into the aspirational wheat based dryland rotation system.
Sub-objective 3a. Continue evaluations of germplasm and potential alternative crops for inclusion into wheat-based dryland systems.
Sub-objective 3b. Evaluate new agronomic practices for inclusion into aspirational wheat-based dryland rotations.
Approach
Dryland farmers in the central Great Plains have the technical means to collect much of the field data needed for precision farm/field management. These data often available in a map format or “data layer” include field grain-yield maps, soil-color maps, electrical conductivity (EC), pH, topographical-elevation field maps, and soil-series maps. However, most dryland producers do not have a science-based, unbiased collection of quantitative recommendations for interpreting how to best use those field data layers. The lack of reliable quantitative recommendations makes it difficult to manage field-scape variability for maximizing net returns. In this project, researchers will use a replicated set of field sized plots that show substantial variability in productivity as one moves through a given field. Using this large field experiment we will develop the mathematical relationships between yield, and inherent field variability and climate variability that are key to a field’s annual productivity. This research will provide a quantitative understanding of how N inputs in dryland rotations can best be optimized across variable field landscapes and variable climate for improving farm gate income. With that science based knowledge researchers will build reliable decision support tools to help guide producers on precision farm management in semi-arid wheat base dryland rotations. This research will also focus on precision optimization of dryland corn populations that match inherent field and climate variability. Soil health monitoring of the rotation treatments and the testing and development of quick methods for assessing soil quality will also be included as important research aspects of the project.
Progress Report
This report is for this new project which began October 2018, and continues reserach from 3010-12210-003-00D,"Adaptation of Dryland Cropping Systems for the Central Great Plains Region to Extreme Variation of Weather and Climate". The unit made progress in selecting 18 fields for the Precision farming project. The 18 fields encompassing over 140 acres were selected for their inherent variability in productivity and because they represent typical fields and soils farmed in the region. Under Sub-objective 1a: Identify and quantify production parameters most important in affecting economic yields across a dryland field-scape we found that 86% of the variability in yield for 4 of the fields could be described by a simple linear regression equation based on field elevation. Specifically, the relationship showed that for every meter of elevation increase above the lowest point in each field, the grain yield declined by 35%. In effect, we found that field elevation within a given field was a good proxy for inherent grain yield productivity. Six fields are being managed using the business as usual protocol of a wheat –fallow reduced till rotation and 12 fields are being managed as a four year aspirational rotation with precision farming methods. In this first year baseline grid sampling of the soil was accomplished in all 18 fields. Soil samples have been analyzed and geo-referenced to make soil variability maps of each of the 18 fields in the study.
Accomplishments
1. Environmental controls and long-term changes on atmospheric carbon stored in the soils of agricultural lands. Agriculture and other land uses can cause decreases or increases in soil organic carbon (SOC) over time. Changes in SOC are likely to vary across soil and climate conditions, yet long-term data to elucidate these trends across different ecosystems remains limited. ARS researchers at Akron, Colorado, in collaboration with scientists from the Universidad Católica de Chile, documented the effects of long-term changes in SOC across a gradient of climate conditions (from arid to humid), soil types, and land uses (non- cultivated, woody perennial, and cultivated) across a long transect of sites in South America. Thus, our objective was to find evidence for SOC changes in the agricultural lands over past three to four decades. Soils were sampled between 2014 and 2016 and analyzed for total C and N content, aggregate stability, texture, bulk density, pH as well as infrared spectroscopy. The SOC contents of each soil were compared to those previously measured at the same sites between 1968 and 1994, covering a wide range of climates and SOC values. Our findings show that the largest SOC losses occurred in semiarid and subhumid areas for the time frame considered, decreasing from their initial C content by 24.7% and 26.1%, respectively. Moreover, cultivated soils in semiarid regions were especially vulnerable. The results also indicated that in cooler and humid regions, the amount of SOC found was stable or increased over time. Among soil orders, soils previously under grassland showed the largest losses (29.9% reduction between sampling dates). The research also showed that soil texture played an important role in the long-term SOC storage in semiarid areas. This study provides a better understanding of the fragility of semiarid agricultural lands in terms of their vulnerability to soil C losses associated with agricultural production, and our results will inform the development of strategies that ensure effective climate change mitigation and long-term soil productivity.
2. Quantifying the effect of the removal of corn stalks left in the field after grain harvest and tillage on soil quality and biological diversity. Tillage and corn stalk or stover harvest (residue removal) are common management practices in corn-based cropping systems around the globe. However, frequent soil disturbance and residue removal are likely to have negative long-term impacts on water conservation, soil structure and belowground biological activity, and there is great concern surrounding the resource sustainability of these practices. In this multi-year study at the Central Great Plains Research Station, ARS scientists at Akron, Colorado, along with university collaborators at Colorado State University, evaluated the effects of tillage and residue removal on the soil earthworm and insect abundance under irrigated corn. Experimental plots were established in 2014 in Akron, Colorado, to understand the impacts of conservation agriculture practices, no-tillage and residue retention, as well as their combined effect. In year three of the experiment soil health parameters were assessed including: soil fauna, aggregate stability, potential infiltration, and chemical fertility measures. The combined practice of residue retention with no-tillage resulted in a five-fold increase in earthworm abundance, enhanced soil structure, and a trend towards greater water infiltration. The data indicates that no-till and crop residue retention practices offer great promise for improving soil structure and water infiltration, and that these effects appear to be mediated by greater earthworm abundance when these two practices are combined. No-till and residue retention practices will improve soil structure and water conservation, and these effects appear to be mediated by greater earthworm abundance when these two practices are combined.
3. Quantification of the relationship between precipitation received and root zone water extraction profiles of dryland crops. The amount of precipitation received, stored in the soil, and the amount used by typical dryland crops are not well defined in the literature. ARS researchers at Akron, Colorado, over a 21-year period evaluated soil water use by winter wheat, dryland corn, proso millet, and pea. Annual precipitation amounts ranged from 228 mm to 629 mm over the 21 seasons evaluated. On average the wheat growing season received 254 mm of precipitation. Wheat used on average 144 mm of the precipitation received, showing a precipitation use efficiency (PSE) of 57%. Similarly the PSE of dryland corn was about 55%. Millet had the highest PSE of 65% and pea had the lowest PSE of 28%. The research documented the relative adaptability of each of the crops to the Central Great Plains region. The research also confirmed that if the root-zone of each crop was divided into 4 sections that most of the water was utilized in about equal portions from the top ½ of the root zone. An inverted conical pattern of water use by all four crops was defined but showed that under semi-arid conditions the first and second depths of each of the crops root-zones were similar in total water used by the crop. About 65 to 70% of total water use was coming from the top half of the root-zone. With an average of 30 to 35 % of the water use coming from the bottom half of the root-zone. This research, combined with soil water measurement data at planting and water-use grain yield production equations also developed by ARS at Akron, Colorado, allows producers farming the 26 million dryland of the Central Great Plains region to determine the economic risk in planting one crop versus another.
4. Organic management and tillage effects on greenhouse gas production in soil. Soils can be source or sinks of atmospheric methane, which is a powerful greenhouse gas which has 25 times the greenhouse gas effect/radiative forcing of carbon dioxide. Methane is produced by soil microbes in the absence of oxygen and typically, waterlogged soils are net producers of methane, while drier soils tend to absorb methane from the atmosphere. However, this pattern is not universal, given that upland soils can sometimes be net sources of methane due to the slow movement of oxygen into the soil. In agricultural systems, there is reason to expect that management practices could alter the amount of soil aeration, and thus affect oxygen-sensitive processes like greenhouse gas production and nitrogen cycling. Based on work at larger scales (e.g., wetlands, sediments), where there are large fluctuations in oxygen availability within the soil, ARS and CSU researchers at Akron, Colorado, hypothesized that methane production is primarily affected by soil moisture and organic matter content. For this project, the team of researchers evaluated methane production in agricultural soils under long-term tillage and organic management. The ARS scientists documented the relationships between soil properties, and methane production, comparing conventional, no-till, and organic management (that included organic amendments), under different soil moistures. The data shows that organically-managed soils tended to produce more methane than conventionally managed soils, and that soil moisture had a significant effect as well. These results show wheat producers that on the dryland fields of the Central High Plains, that organic management with organic amendments can improve soil quality. On the other hand, the increased soil quality is accompanied by an increased emission of the greenhouse gas methane, which is important in the context of climate change.
Review Publications
Zhang, Y., Hansen, N., Trout, T.J., Nielsen, D.C., Paustian, K. 2018. Modeling deficit irrigation of maize with the DayCent Model. Agronomy Journal. 110:1-11. http://doi:10.2134/agronj2017.10.0585.
Nielsen, D.C., Vigil, M.F. 2018. Soil water extraction for several dryland crops. Agronomy Journal. 110:2447-2455. https://doi.org/10.2134/agronj2018.05.0335.
Nielsen, D.C., Vigil, M.F. 2018. Dry bean water use/yield production function to estimate yields in the Central Great Plains. Field Crops Research. 228:60-67. https://doi.org/10.1016/j.fcr.2018.08.016.
Ramirez, P., Calderon, F.J., Fonte, S., Bonilla, C. 2018. Environmental controls and long-term changes on carbon stocks under agricultural lands. Global Change Biology. 186:310-321. https://doi.org/10.1016/j.still.2018.10.018.
Kallenbach, C.M., Contant, R., Calderon, F.J., Wallenstein, M.D. 2019. A novel soil amendment for enhancing soil moisture retention and soil carbon in drought-prone soils. Geoderma. 337: 256-265. https://doi.org/10.1016/j.geoderma.2018.09.027.
Matamala, R., Jastrow, J.D., Calderon, F.J., Liang, C., Fan, Z., Michaelson, G., Ping, C. 2019. Predicting the decomposability of arctic tundra soil organic matter with mid infrared spectroscopy. Soil Biology and Biochemistry. 129:1-12. https://doi.org/10.1016/j.soilbio.2018.10.014.
Melman, D.A., Schneekloth, J., Courtland, K., Calderon, F.J., Fonte, S.J. 2019. Tillage and residue management drive soil quality and functional changes in an irrigated cropping system of Eastern Colorado. Applied Soil Ecology. 143: 98-106. https://doi.org/10.1016/j.apsoil.2019.05.022.
Trimble, B.R., Calderon, F.J., Poulson, S., Verburg, P.S. 2018. Land conversion to irrigated agriculture reduces labile and increases recalcitrant carbon in a semi-arid Nevada soil. Soil Biology and Biochemistry. 2:3-38. https://doi.org/10.3390/soilsystems2030038.
Brewer, P., Calderon, F.J., Vigil, M.F., Von Fischer, J. 2018. Impacts of moisture, soil respiration, and agricultural practices on methanogenesis in upland soils as measured with stable isotope pool dilution. Soil Biology and Biochemistry. 127:239-251. https://www.sciencedirect.com/science/article/pii/S0038071718303092?via%3Dihub.
