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.
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.
This is the second progress report for project 3010-12210-004-00D. The following activities were carried out to fulfill Objective 1: ARS researchers at Akron, Colorado, have established research plots for the Precision Farming project and have made a series of important measurements to relate crop yield variability to soil, elevation and plant variables. We have also defined management zones according to yield variability and have begun a series of soil moisture measurements in order to see how the high yielding areas differ from the lesser yielding areas in their crop water use efficiency. Even with COVID-19, thousands of soil samples from the grids have been scanned for infrared spectroscopy and analyzed for general soil properties, which has allowed us to create geospatial maps of soil quality. Multi-year tractor based wheat and corn yield data have also been used in conjunction with elevation maps to generate geospatial layers of crop yield variability. The installation of the eddy covariance towers is in progress, with one in place and a second one on the way. All these activities are allowing the ARS researchers to set the stage for a long-term study comparing business as usual wheat production systems to a more intense and precision managed multi crop rotation. Research activities pertaining to Objectives 2 and 3 are on hold, awaiting the refilling of critical scientist vacancies.
1. Tillage and residue management affect corn yields and water conservation in a semiarid cropping system. Residue removal from corn fields offers an opportunity to increase farmer profits, but potential tradeoffs for water availability and crop performance merit evaluation. This multi-year study is a collaboration between ARS researchers in Akron, Colorado, and scientists from Colorado State University. The project compared the effects of two tillage practices (no-till and conventional) and two corn residue management practices (harvested vs. retention) on grain yields, water infiltration, evaporation, and soil quality. Maize grain yields under limited irrigation were increased with residue retention between 2016-2018, but tillage had no significant effect. Water infiltration into the soil was higher with residue retention. Water losses due to evaporation and crop use were reduced by the combination of no-till and residue retention. Soil compaction was significantly reduced by both tillage and residue retention. Water content in the soil at planting was higher with residue retention. These results suggest that corn residue removal would on average require additional irrigation relative to the residue retention treatment. These results will help irrigated corn growers in the region make better residue management decisions. In summary, our findings suggest that high rates of crop residue removal under limited irrigation in a semiarid environment can negatively affect water conservation and yields, and that tradeoffs surrounding residue export need to be considered.
2. Long-term evidence shows that crop diversity enhances agricultural resilience. A grand challenge facing humankind is how to grow enough grain for an increasing population in the context of a changing climate and soil degradation. ARS researchers in Akron, Colorado, in collaboration with scientists from University of California, Berkeley and several other Universities compiled 347 site-years of yield data from 11 experiments across North America to evaluate the benefits of crop diversification on corn yields. Statistical analysis of long-term crop yield datasets across a continental precipitation gradient were used to assess how crop diversification affects maize yields. More diverse rotations increased maize yields over time and across all growing conditions (28.1% on average), including in favorable conditions (22.6%). Notably, more diverse rotations also showed positive effects on yield under unfavorable conditions such as drought, whereby yield losses were reduced by 14.0%–89.9%. Crop-rotation diversification can thus be considered a risk-reduction strategy for food production, with the potential to stabilize yields in future years nationwide. With these results, grain producers nationwide will be compelled to rethink their crop rotations in order to enhance corn production.
3. Development of useful soil quality indicators across a wide geographic range. An ARS researcher in Akron, Colorado in collaboration with Colorado State University, and Universidad Catolica de Chile scientists evaluated several soil quality measurements for a wide range of land uses and soil types. The team evaluated two laboratory assays that have been proposed as potential soil quality indicators in agricultural fields. One assay (LF) measures light fragments of soil organic matter and decomposing plant residues, while the the second assay (POXC) includes the soil organic matter that is easy to decompose by microbes. The amount and variability of POXC and LF, and their relationship with soil quality at regional scales have not been thoroughly studied. The aim of this study was to examine the chemical traits associated with POXC and LF in samples collected from 75 widespread locations under different soil types, land use and climates. Our results show that LF had different chemical makeup in cool and rainy areas compared to warmer areas. The study also showed that POXC and soil C content were closely related, and changes in POXC were affected by variations in climate conditions. Thus, both measurement can be regarded as sensitive measures of soil quality, but also to environmental and management factors. This understanding of the variability of new soils assays at larger geographical scale will allow scientists and extension agents to evaluate sustainable land management options for the prevention of land degradation in the context of adaptation to climate change.
4. Soil physicochemical properties influenced by nitrogen sources and rates in the central Great Plains. Soil fertility is influenced by nitrogen sources and rates in the central Great Plains. Manure applications can potentially benefit soil chemical properties, provide plant nutrients, and improve agricultural sustainability. This study was a collaboration between ARS researchers in Akron, Colorado, and researchers at Kansas State University. In this multi-year study, the effects of cattle manure applications on soil chemical properties were evaluated under different tillage managements. After 10 years, annual addition of cattle manure significantly increased soil nitrogen, phosphorus and potassium compared with chemical fertilizer treatments. Soil electrical conductivity, which is a good indicator of soil quality, was affected by manure treatments due to several manure-associated nutrients such as calcium, magnesium, sodium, and chloride. In the dryland cropping systems, significant changes in soil chemical properties may take longer than ten years of management to be observed. In general, growers should take extra care to prevent soil phosphorus accumulation specifically when cattle manure is being added to meet the nitrogen requirement for crop production. Future best management practices could include reductions in manure application frequency or reducing manure application rate to prevent excessive phosphorus accumulations and avoid the risk of phosphorus runoff, while obtaining the benefits of manure application.
5. Optimum rates of surface-applied coal char decreased soil ammonia volatilization loss. In an agricultural system, nitrogen fertilizer (N) addition could be susceptible to loss through leaching or be lost as gas to the atmosphere as nitrous oxide or ammonia. The addition of high carbon (C) material, such as char to the soil, may reduce soil N losses. This study was accomplished in collaboration between ARS researchers in Akron, Colorado, and researchers at University of Nebraska-Lincoln. The objective of this study was to evaluate the effects of char addition on N losses to the atmosphere and through leaching to the ground water. A 30-day laboratory study was conducted using two soil types, loam and sandy loam soils that were fertilized with urea ammonium nitrate. Five different char rates were applied to both soils. The addition of char significantly reduced ammonia volatilization by approximately 8.7% for loam soil and by 11% for sandy loam soil compared with no char treatment. Char addition did not change nitrous oxide emissions or nitrate leaching values compared with control treatments. Fertilizer addition increased nitrous oxide emission by an average of 10-fold and nitrate leaching by an average of two-fold compared with unfertilized soil. Nitrate leaching was greater in the sandy loam compared with the loam soil. Addition of high C content products such as char at optimal rates have the potential to reduce agricultural reactive N to the atmosphere by decreasing gaseous N losses from fertilized soils. This research is of interest to the general public due to the implications for atmospheric greenhouse gas mitigation and nitrogen contamination in surface waters.
6. Soil chemical properties after 12 years of tillage and crop rotation. Soil properties are affected by tillage and crop rotation. Conservation tillage and/or zone tillage are being implemented with crops in rotation to address some of the concerns regarding soil quality parameters and land sustainability. In this multi-year study, an ARS scientist at Akron, Colorado, with University of Nebraska collaborators, evaluated the impact of different tillage practices and crop rotations on: (1) crop yields; (2) chemical properties; and (3) particulate soil organic matter (POM). Tillage practices were notillage (NT); zone tillage (ZT); and Plow. Crops in rotation were corn, dry bean, and sugar beet, organized in 3- or 4-year rotations. The crop yields were influenced by the type of previous crop. For example, in corn following dry bean, corn had the highest yield when compared with other rotations. Whereas, corn following corn had an average yield reduction of 30%. Corn yield following dry bean was significantly greater by approximately 14% when compared with corn yield following sugar beet. The sugar beet yield was enhanced by tillage when compared with NT practices. Rotations with corn following dry bean had higher soil organic matter compared with corn following sugar beet. Soil POM was higher with NT by 32% and with ZT by 17% compared with plow. Nebraska and Colorado are among the top sugar beet producing states in the USA. Results show that in the rotations that include sugar beet, addition of organic amendments could be used to prevent soil degradation.
7. Effects of a new soil amendment derived from cheese production on grain yields. An ARS researcher in Akron, Colorado, in collaboration with Colorado State University scientists evaluated the use of a cheese byproduct on wheat and corn yields in Eastern Colorado. Using industrial byproducts to improve soil health can benefit farmers and the cheese industry by offering a viable opportunity to improve soils and efficiently manage waste. Our results show that lactobionate, a byproduct of the cheese industry can improve soil water holding capacity and nutrient availability in the laboratory. We also evaluated lactobionate in the field for potential improvements in key soil health indices, focusing on soil moisture, carbon, and nitrate. Lactobionate was applied at 5 rates. Four weeks after broadcast application in the wheat trial, we observed a significant increase in soil moisture and a decrease in soil nitrate. In the top soil we also saw a non-significant 14% increase in corn yield with lactobionate. Observed no other changes in soil properties measured in the corn trial. Our observations suggest the potential for lactobionate to modify soil water content, soil microbiology, available nitrogen, and yield. While recycling food byproducts for use as a soil amendment may have benefits for key soil health parameters, the timing, mode and application amounts need to be optimized for maximal effects of lactobionate.
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Bowles, T.M., Mooshammer, M., Socolar, Y., Calderon, F.J., Cavigelli, M.A., Culman, S.W., Deen, W., Drury, C.F., Garcia Y Garcia, A., Gaudin, A., Harkcom, W., Lehman, R.M., Osborne, S.L., Robertson, G., Salerno, J., Schmer, M.R., Strock, J., Grandy, A. 2020. Long-term evidence shows crop rotation diversification increases agricultural resilience to adverse climate conditions in North America. One Earth. 2:284-293.