Evaluating the Impact of Wheat Straw Amendments on Dryland Organic Wheat Systems

Progress report for GW22-244

Project Type: Graduate Student
Funds awarded in 2022: $29,995.00
Projected End Date: 08/31/2024
Host Institution Award ID: G232-23-W9212
Grant Recipient: Utah State University
Region: Western
State: Utah
Graduate Student:
Principal Investigator:
Principal Investigator:
Dr. Jennifer Reeve
Utah State University
Expand All

Project Information


Western dryland organic wheat production accounts for 49% of all organic wheat produced in the United States. These systems are constrained by limited inputs and low precipitation, leading to declines in wheat yields and soil health. Compost is an effective soil amendment resulting in yields two times higher than control plots 24+ years following a single application, but results are inconsistent. Growers are concerned by this inconsistency because the compost prices are high.

Research has shown that in dry years 80% of the benefit realized from the compost amendment is due to improvements in soil physical health, including improved soil water-holding capacity, infiltration rates, penetration and soil aggregation - critical under dryland systems where two years of water produce one crop. Thus growers asked whether applying lower quality amendments such as wheat straw might improve soil physical health at a lower cost than compost, as has been demonstrated with dry-stacked manure. Straw, however, has a much lower nitrogen content than stacked manure or compost. Nitrogen is required by both the wheat and soil microbes. Nitrogen competition and amendment-induced changes in microbial community diversity and populations, could lead to decreases in grain yield and protein content. Therefore, we will also analyze microbial community diversity, respiration and function to better understand the complex C/N dynamics in the soil environment.

This research will contribute to understanding the most cost-effective way for dryland organic wheat farmers to improve soil physical health while maintaining or improving wheat yields and quality.

Project Objectives:

Research Objectives:

Objective 1: Determine if straw can be used as a suitable replacement for compost while providing the same benefits to soil physical health and crop yield through increased SOM.

Objective 2: Determine the impact of straw on microbial population diversity and microbial substrate use efficiency as a measure of soil biological health.

Educational Objectives:

Objective 1: Adoption of sustainability practices through result sharing and education.

Objective 2: Undergraduate involvement, education, and project presentations.


Click linked name(s) to expand/collapse or show everyone's info
  • David Deakin - Producer
  • Richard Grover - Producer


Materials and methods:

Random complete block design/ Plot layout

New plots were established in 2021 at Mr. Grover’s farm in Snowville, UT. This site is home to multiple projects studying the short- and long-term effects of compost amendment and has been certified organic since 1992.  Treatments are arranged in a randomized complete block split plot design with 4 treatments and a control: Hardwood + manure compost (HWC), Softwood + manure compost (SWC), paunch manure compost (MC), wheat straw (WS), and control (NC) with no amendment. All compost amendments were applied at a rate of 50 Mg/ha. Clean wheat straw was applied at 5tons/ha, this rate is approximately 2x the rate of wheat straw returned to soil after harvest in conventional systems (Gross, 2016). To assess the effects of N availability on soil microbial populations and microbial substrate use efficiency, 50 Mg/ha of N as Feather Mill was applied to the split plot on each treatment including the control. This amount of N is higher than what is typically recommended for dryland systems, but we wanted to ensure we saw treatment results in the event of leaching due to snow melt in the spring. This will also allow us to see if the high C/N ratio of wheat straw is leading to N immobilization through microbial degradation. Whole plot size is 7.3 x 15.24 m. Compost will be applied only once over the duration of the experiment. Sites will be under conventional tillage and wheat will be planted at 150 to 200 live kernals/m2/a in fall (Aug.-Oct.). Openers on planters include both disk-furrow hoe designs to facilitate seed placement into moisture. Plots will be harvested with a small plot combine in July or Aug. of the following year (2022, 2024).

            Objective 1: Determine if straw can be used as a suitable replacement for compost while providing the same benefits to soil physical health and crop yield through increased SOM.

            Hypothesis: Wheat straw can be used as an alternative to compost while increasing yield and soil physical health through increased SOM.

Assessing soil physical health:

Soil organic matter (SOM) is generally considered integrally tied to many indicators of soil health and is one of the most significant single indicators of soil quality and crop productivity (Reeves, 1997). Soil organic carbon (SOC) and SOM have a major impact on physical and chemical indicators of soil and can influence the nutritive and non-nutritive benefits associated with these indicators. In relation to non-nutritive benefits, SOM improves the physical structure of soil by increasing aggregation and aggregate stability. SOM has been shown to decrease bulk density. This reduces soil compaction and increases water infiltration. This also improves surface structure and decreases the formation of surface crust development. With this, soil is less susceptible to erosion from wind and rain. A common method for increasing SOM is through the application of compost. Benefits of increased SOM on soil physical structure have been extensively outlined by many researchers (Tisdall and Oades, 1982; Abiven et al., 2009; Six et al., 2004).

A paper published by Stukenhotlz (2002) looked at nutritive and non-nutritive interactions on wheat yield in dryland organic wheat systems in Snowville, Utah. Compost was applied as a soil amendment in an effort to help reinstitute soils nutrients and organic matter that were deficient due to continuous cropping with little input. In this study, soil moisture retention was the main non-nutritive factor observed. Increasing organic matter and improving soil water retention increased yield, especially in years with below average precipitation. Other non-nutritive benefits in relation to soil physical indicators might include increases in soil aeration, cation exchange capacity, soil pH buffering capacity, aggregation and aggregate stability, infiltration, and soil strength (Reeves, 1997).

Physical properties of soil, specifically aggregation and aggregate stability, increase the long-term stability of SOC (Six et al., 2000). Aggregation and aggregate stability influence physical structure of soil by improving soil porosity which influences soil water movement and moisture retention. Improved soil structure also reduces erosion and surface crusting while improving root penetration and development and yield (Bronick and Lal, 2005). Aggregation and aggregate stability impact many of the physical indicators of soil health. Increased aggregation and aggregate stability have been shown to reduce erosion, increase root penetration, increase water infiltration, decrease surface crusting, and improve overall soil health and yield potential in agricultural soils (Franzluebbers, A. 2002). In addition, aggregates can physically protect SOM. This is through occlusion of SOM which protects C from microbial decomposition (Six et al., 2004). Recent work conducted at USU has shown enhanced soil aggregates with time (figure 1) in response to compost plays a key role in improving soil moisture infiltration but also protects organic C microbial breakdown. In fact, enhanced soil C is likely explained at least in part by this mechanism.

Wheat yield and quality:

Previous studies have shown that wheat yield response can vary depending on rate and type of amendment in dryland organic wheat systems (Calderón et al., 2018; Lyon & Hergert, 2012; Deakin, 2021). Yield and grain quality data will better demonstrate the economic benefits of amendments and allow the growers to visualize returns or deficits for each amendment type. Determining yield and quality of grain will allow us to better understand the economic benefits of these different types of amendments.


Soil health:

Most of the baseline standard soil tests have been completed on control plot samples collected in April 2022 at 0-30 and 30-60 cm depth, using methods described in Soil and Plant Reference Methods for the Western Region (Gavlak et al., 2003). Baseline testing completed includes Olsen P, DTPA-extractable elements (Fe, Zn, Cu, Mn); and total organic C using PrimacsSLC instrument (Skalar Inc., Buford, GA). Testing to be completed includes electrical conductivity (EC) (Method S2.30), pH, cation exchange capacity (Method S10.10), and total N using PrimacsSN instrument (Skalar Inc., Buford, GA).

Samples from the compost and feather meal-treated plots were also collected in April 2022 during the wheat phase of the rotation, at 0-30 and 30-60 depths, and analyzed for nitrate and ammonium (Lachat, Hach company, Loveland, CO), Olsen P (Gavlak et al., 2003), dissolved organic C and N measured in in water extracts (TOC/TN analyzer, Shimadzu Scientific Instruments, Lenexa, KS), and TOC and N as described above. Due to drought conditions and the short sampling window prior to dry down, 60-90 cm samples could not be collected.  Soil quality indicators that will be analyzed on samples collected at 0-10 cm include TOC and N as described above, and readily mineralizable C and N.

In April 2022 we also analyzed soil physical health indicators. Soil water infiltration was tested using a Cornell Sprinkle Infiltrometer (Moebius-Clune et al., 2016). Soil aggregate stability was assessed on to 0-10 cm samples according to Kemper and Rosenau (2006). Surface crust development and compaction was analyzed using a FieldScout SC 900 Soil Compaction Meter. Bulk density was measured according to Blake (1965) and soil moisture was tested gravimetrically.

Wheat Yield and Quality;

We planned to monitor wheat growth in plots by measuring tillers per plant on 10 randomly selected plants per plot, heads per plant for those 10 plants, seeds per head (two per plant), and 1000 kernel weight immediately prior to harvest. Wheat yields were to be determined by harvesting each plot with a plot combine. Quality measurements for each plot were to include test weight, 2 g mixograph, and lactic acid sedimentation. However, due to severe drought conditions and weed pressure during the 2022 cropping cycle, no 2022 wheat crop was harvested. Therefore, data for wheat yield and quality were not collected. 

Aggregate Stability data 2021

Figure 1: Data represents aggregate stability measurements in % stable aggregate (y-axis). Amendment type and rate in Mg/ha is represented on the x-axis. 0 (control), 12.5, 25, 50 represent rate of compost; chicken manure (CHM); Positive control (PC) and correlate with the year of application (2016 & 2020). Samples were collected in 2021 and analyzed for stability according to Kemper & Rosenau (2006).

            Objective 2: Determine the impact of straw on microbial population diversity and microbial substrate use efficiency as a measure of soil biological health.

Soil organic matter and soil biological properties are closely tied to the physical and chemical properties of soil. Microbial population diversity and microbial use efficiency influences plant and soil health through nutrient cycling dynamics on the community level. Compost amendments have been shown to introduce non-native species to the natural microbial populations. There are cases where this has been shown to be advantageous through increasing microbial diversity and activity (Farrel et al., 2010). However, other studies have shown that introducing non-native species can decrease functionality of native populations through competition. (Trabelsi & Mhamdi, 2013). Gaining a better understanding how amendment type influences native and non-native microbial community dynamics and its relation to function can have impacts on recommendations of amendments type for these agricultural systems.

 Microbial use efficiency offers insight into C and N dynamics in the system. Microbial decomposition rates of SOM can be influenced by the C/N ratio found in soils. Microbes will have to work harder to break down OM with a higher C/N ratio resulting in increased CO­2 production. This has significant impacts on atmospheric C levels by reducing the amount of CO2 which contribute to global warming (Cumhur & Malcolm, 2008). Microbial decomposition of OM increases nutrient availability for plants, but the efficiency at which this is done can depend heavily on the soil to microbial C/N ratio. High C inputs with little N can inhibit microbial efficiency and can lead to the immobilization of N. Testing for potential nitrification and anaerobic N mineralization will also allow us to better understand this complex C/N microbial dynamic. Microbial respiration data will be an important aspect of the C/N soil/microbial dynamic. Quantifying microbial use efficiency and microbial biomass through respiration tests will allow us to further assess the implications of possible N immobilization

Microbially mediated nutrient cycling plays a critical role in soils with relatively low available nutrients which is often the case in dryland organic wheat systems. Enhancing microbial diversity in agricultural systems can increase soil organic matter turnover, soil enzyme activity, and contribute to soil fertility (Tautges et al., 2016). Results published by Zhang (2014) showed that compost significantly increased soil microbial biomass and increased root weight and development in cucumber plant, these effects were attributed to the improvement of soil microbial properties and increased nutrient availability. However, there is little research on the impact amendment type has on soil microbiology communities and function in dryland organic agricultural systems. Previous research has shown differences in yield response and protein content when different amendments were applied in dryland systems (Deakin, 2021). This could be due to differences in microbial communities introduced with the amendment. Understanding these community differences can answer questions regarding the differences in yield and grain quality observe in response to amendment type.


Microbial community diversity and function:

Soil samples were collected from 0-10 cm in the spring of 2022, DNA extractions are currently in progress using a Qiagen DNeasy PowerMax Soil Kit. Extracted samples will be stored in -80°C freezer until PCR tests can be performed. Microbial community diversity and quantitative PCR analysis will be performed, and results reported by Utah State University Center for Integrated Biosystems. Basal respiration and microbial biomass were analyzed on 2022 samples according to Anderson & Domsch (1978). Dehydrogenase and phosphatase enzyme activity were determined using the Tabatabi method (1994) on the 2022 0-10 cm samples. Understanding nitrogen mineralization will be necessary for assessing whether or not N is immobilized due to high C/N ratios. Potential nitrification and anaerobic nitrogen mineralization will be assessed according to Schmidt & Belser (1994).         


Abiven, S., Menasseri, S., & Chenu, C. (2009). The effects of organic inputs over time on soil aggregate stability – A literature analysis. Soil Biology and Biochemistry, 41(1), 1        12. https://doi.org/10.1016/j.soilbio.2008.09.015

Anderson, J.P.E. & Domsch, K.H.. 1978. A physiological method for the quantitative measurement of microbial biomass in soil. Soil Biol. Biochem. 10:215–221. doi:10.1016/00380717(78)90099-8

Bronick, C. J., & Lal, R. (2005). Soil structure and management: a review. Geoderma124(1-2), 3-22.

Calderón, F. J., Vigil, M. F., & Benjamin, J. (2018). Compost input effect on dryland wheat and forage yields and soil quality.  Pedosphere, 28, 451–462.  https://doi.org/10.1016/S1002-0160(17)60368-0

Cumhur, A. & Malcolm, S. C. (2008). The effects of global climate change on agriculture. American   Eurasian J. Agric. and Environ. Sci3(5), 672-676.

Deakin, M. D., (2021) Compost and Cover Crop Effects in Dryland Organic Wheat. All Graduate Theses and Dissertations. 8103. https://digitalcommons.usu.edu/etd/8103

Farrell, M., Griffith, G. W., Hobbs, P. J., Perkins, W. T., & Jones, D. L. (2010). Microbial diversity and activity are increased by compost amendment of metal-contaminated soil. FEMS Microbiology Ecology, 71(1), 94–105. https://doi.org/10.1111/j.1574-6941.2009.00793.x

Franzluebbers, A. (2002). Water infiltration and soil structure related to organic matter and its stratification with depth. Soil and Tillage Research, 66(2), 197–205. https://doi.org/10.1016/s0167-1987(02)00027-2

Gavlak, R., D. Horneck, R.O. Miller, and J. Kotuby-Amacher. 2003. Soil, plant and water reference methods for the western region. 2nd ed. WCC-103 Publ. Colorado State Univ., Ft. Collins.

Gross, P. (2016, June 8). What’s the nutrient value of wheat straw? Michigan State University/ MSU Extension. Retrieved February 9, 2022, from https://www.canr.msu.edu/news/whats_the_nutrient_value_of_wheat_straw

Kemper, W. D., & Rosenau, R. C. (1986). Aggregate stability and size distribution. Methods of soil analysis: Part 1 Physical and mineralogical methods, A. Knutes (Ed) 5, 425-442. https://doi.org/10.2136/sssabookser5.1.2ed.c17 from http://www.nrcs.usda.gov/wps/portal/nrcs/main/soils/health/

Lyon, D. J., & Hergert, G. W. (2012). Nitrogen fertility in semiarid dryland wheat production is challenging for beginning organic farmers. Renewable Agriculture and Food Systems, 29, 42–47. https://doi.org/10.1017/S1742170512000324

Reeves, D.W. (1997) The role of soil organic matter in maintaining soil quality in continuous cropping systems. Soil Till Res 43: 131–167

Schmidt, E.L. and Belser, L.W. ( 1994).  Autotrophic nitrifying bacteria.  pp. 159-177 In Methods of Soil Analysis, Part 2.  Microbiological and Biochemical Properties –SSSA Book Series, no. 5.  Soil Science Society of America, Madison, WI.

Six, J., Bossuyt, H., Degryze, S., & Denef, K. (2004). A history of research on the link between (micro) aggregates, soil biota, and soil organic matter dynamics. Soil and Tillage Research79(1), 7-31.

Six, J., Paustian, K., Elliott, E. T., & Combrink, C. (2000). Soil Structure and Organic Matter I. Distribution of Aggregate-Size Classes and Aggregate-Associated Carbon. Soil Science Society of America Journal, 64(2), 681–689. https://doi.org/10.2136/sssaj2000.642681x

Stukenholtz, P. D., Koenig, R. T., Hole, D. J., & Miller, B. E. (2002). Partitioning the nutrient and nonnutrient contributions of compost to dryland-organic wheat. Compost science & utilization10(3), 238-243.

Tabatabai, M.A. 1994. Soil enzymes. p. 775–833. In R.W. Weaver et al. (ed.) Methods of soil analysis. Part 2. Microbiological and biochemical properties. SSSA, Madison, WI.

Tautges, N. E., Sullivan, T. S., Reardon, C. L., & Burke, I. C. (2016). Soil microbial diversity and activity linked to crop yield and quality in a dryland organic wheat production system. Applied Soil Ecology, 108, 258–268. https://doi.org/10.1016/j.apsoil.2016.09.003

Tisdall, J. M., & Oades, J. M. (1982). Organic matter and water‐stable aggregates in soils. Journal of soil science33(2), 141-163. doi:10.1111/j.1365-2389.1982.tb01755.x

Trabelsi, D., & Mhamdi, R. (2013). Microbial Inoculants and Their Impact on Soil Microbial Communities: A Review. BioMed Research International, 2013, 1–11. https://doi.org/10.1155/2013/863240

Zhang, X., Cao, Y., Tian, Y., & Li, J. (2014). Short-term compost application increases     rhizosphere soil carbon mineralization and stimulates root growth in long-term            continuously cropped cucumber. Scientia Horticulturae, 175, 269–277.  https://doi.org/10.1016/j.scienta.2014.06.025

Research results and discussion:

In April-May of 2022 Preston Christensen and his team collected soil samples for all the laboratory analyses. All the 0-10 cm, 0-30 cm, and 30-60 cm  samples were collected, however, following 2 years of drought, even in early spring the soil was too dry to sample down to 90 cm. Field measurements with the penetrometer and Cornell Infiltrometer were collected following snowmelt in spring of 2022. The measurements were difficult due to wind at the site which also caused a rapid dry down that spring, but Preston and his undergraduate assistant (Greg Vandas) were able to trouble shoot the method. Preliminary results of soil penetration water infiltration, and stable aggregation indicate that the softwood compost is having the greatest effect on the soil physical properties. These results were shared in a poster presentation (Christensen-Presentation-for-SSSA-Anual-Meeting-2022) at the Soil Science Society of America meetings in Baltimore in November 2022.

Due to the severe drought in Utah in 2022, no crop could be harvested that year and 2023 is a fallow year for Preston’s research plots. Therefore, there is no grain yield data from 2022. However, Preston Christensen and his undergraduate lab assistants have been analyzing the soil samples he collected from all the plots at the 0-10 cm, 0-30 cm and 30-60 cm depths in spring 2022. To date, Preston has completed measurements of bulk density, Olsen P, DOC, aggregate stability, and gravimetric water content analyses. TOC measurements are in progress, and nitrate and ammonia samples have been extracted and are pending analysis. Olsen K still needs to be completed as does DTPA extractable elements. Base chemical and physical soil health analyses were determined through testing of research control plots for the 2022 sampling. Baseline values for the microbial soil health are currently in progress. Preston expects that all the sample and data analyses will be completed before the next sampling cycle starts circa March 2024.


Participation Summary
2 Producers participating in research

Research Outcomes

Recommendations for sustainable agricultural production and future research:

As the data are preliminary, we have no recommendations as yet.

1 Grant received that built upon this project
1 New working collaborations

Education and Outreach

1 Webinars / talks / presentations
1 Workshop field days

Participation Summary:

4 Farmers participated
6 Ag professionals participated
Education and outreach methods and analyses:
  • One Grower Advisory Meeting was held on March 21, 2023 at which Preston Christensen’s preliminary results were presented and discussed.
  • Five undergraduate students have been trained on physical, chemical and biological measures of soil health by Preston Christensen.
  • One undergraduate, Mark Kindred was recruited to Jennifer Reeve’s MS program in Organic and Sustainable Agriculture. Two other students, Cassidy Sawdon and Maia Garby are strongly considering applying for graduate degrees in Soil Science at USU after working with Preston on his WSARE research.
Education and outreach results:
  1. Adoption of sustainability practices through result sharing and education. Although Preston’s research is still quite preliminary, he did present the results of his research on soil physical health (soil structure, aggregate stability, and water infiltration) based on the amendment of a dryland wheat soil with wheat straw, a complete compost, softwood compost, hardwood compost and wheat straw at the Soil Science Society of America Annual Meetings in Baltimore in November 2022. On March 21, 2023, the preliminary results of Preston’s research was presented and discussed at a Growers Advisory Meeting for dryland wheat held at USU. Following two years in a row in which the growers lost their wheat crops due to drought resulting in no growth/harvest (2022) and poor stand/weeds (2023) the growers were encouraged by the findings that compost lead to improved soil physical health and that the softwood compost seems to be having the greatest effect.


  1. Undergraduate involvement, education, and project presentations. Preston Christensen has been working with undergraduate students and training him to help him on the methods necessary to complete his research since his graduate program began. In 2022, Preston trained Greg Vandas to help him run the field infiltrometer measurements and Brady Christianson to help with aggregate stability analyses. In 2023 he trained newly hired post-doc Idowu Atoloye how to do both the infiltrometer and aggregate stability measurements for another project.  In the lab, Preston trained Cassidy Sawdon to perform the enzyme assays, Kayla Hansen to analyze DOC and Mark Kindred to analyze respiration and dehydrogenase. Mark is now enrolled in an MS program under Jennifer Reeve at USU. Cassidy is also considering enrolling in a MS program after working with Preston. Since August 2023, Maia Garby has been helping Preston analyze the soil samples he collected in spring 2022 for 16sRNA. She will also help him complete the analyses of Olsen K, pH and EC on the same samples. Maia is strongly considering starting a graduate program in soil microbiology at USU. In addition to helping Preston complete all the analyses necessary for his research, giving undergraduate students to opportunity to participate in field and lab research with the larger objective of expanding their experiences, career potential and possible graduate degrees is being realized with this WSARE grant.
Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.