Kernza in Wyoming: Evaluating Perennial Grains to Revitalize Wyoming Dryland Agriculture

H. Rodgers, J. B. Norton, L. T. Van Diepen
University of Wyoming, Ecosystem Science & Management
Introduction
Semiarid grains: our most important crops in our most vulnerable landscapes
  • Wheat constitutes 1/5 of the global food supply6
  • Wheat is mainly grown in semiarid landscapes, which are particularly vulnerable to climate change and land degradation1
  • Drought, land degradation, and fluctuating markets drive land abandonment in the Western Great Plains4
Kernza (left) grows a deeper, denser root system than wheat (right).13
Natural Systems Agriculture: mimicking the native ecosystem
  • Deep-rooted perennial grasses can mimic the native prairie of the Great Plains
    • Converting tilled wheat-fallow to perennials in eastern Wyoming can restore SOC to 90% of that under native grassland after 15 years10
  • Kernza could provide some benefits of perennial prairie while still producing food. Kernza is:
    • The first perennial grain crop grown in the US
    • Serves as an alternative to annual wheat
    • Harvested from a cultivar of intermediate wheatgrass (Thinopyrum intermedium)
  • Kernza's deep roots sequester C, curtail soil erosion, and support microbial communities more similar to native prairie than to annual wheat8,11
  • Soil health benefits and lower input costs could make Kernza an economically viable option for High Plains wheat farmers, despite lower yields
Aims
  • Evaluate the impact of Kernza on soil health, soil microbiology, and C sequestration compared to wheat-fallow and Conservation Reserve Program (CRP) systems
  • Determine which soil and soil microbial properties could serve as rapid, reliable indicators of changing soil health in this system
Methods
Site Description
  • Location: High Plains Region of SE Wyoming
  • Precipitation: 305-432 mm
  • Temperature: mesic regime (average min/max: -13/4°C Jan, 11/31°C July)
  • Soil: mainly Mollisols & Entisols
Baseline soil samples were taken in CRP (left), wheat (right), and fallow (not shown) in Spring 2021
Experimental Design
  • Planted or will plant 10-20 acres of Kernza on each of 4 farms in Spring 2021/ 2022
  • Measure Kernza and wheat yield by plot combine starting Summer 2022
  • Sample soil at matched Kernza, wheat-fallow, and CRP plots at one farm at two depths (0-5 and 5-15cm) each Spring
Soil Analyses
Organic Matter Pools
dissolved organic C & N (DOC & N)
soil protein
permanganate oxidizable C (POXC)
potentially minerealizable N (PMN)                                        
nitrate
total C & N
Biological Properties
microbial biomass C & N (MBC & N)
activities of 9 soil enzymes involved in the cycling of C (BG, AG, BX, CBH), N (NAG, LAP), sulfur (SUL), or phosphorus (PHOS)
phospholipid fatty acids (PLFAs)
Chemical & Physical Properties
pH & EC 
porosity
water-stable aggregates
Soil samples were divided into two depths (0-5 and 5-15cm)
 
Discussion & Conclusions
Conclusions, Supporting Research, & Future Expectations
  • Kernza has been found to support higher soil fungi, AMF, and total microbial biomass 2,5,8,12
  • BG, SUL, soil protein, and PMN may be particularly sensitive soil health indicators in these systems
    • Labile C pools are an early soil health indicator in systems transitioning to Kernza3,12
  • Stratification of microbial activity and labile organic matter pools could be a rapid, reliable indicator of changing soil health as annual cropland transitions to perennials
    • Surface SOC can promote functions such as erosion control and nutrient conservation7,9
    • Even though this study may be too short to find measurable increases in SOC, if the soil under Kernza starts becoming more similar to that under CRP, that could indicate longer term improvements in soil health and C sequestration
Going forwards, these results will help us to better interpret what these various soil health indicators can tell us about land use change and soil health as fields transition from an annual to a perennial grain crop
 
Acknowledgements
This project was funded by Western Sustainable Agriculture Research & Education (SARE). Special thanks to all members of the Norton and Van Diepen labs for their support in the field and lab.
 
Citations
1. Asseng, S. et al. Rising temperatures reduce global wheat production. Nat. Clim. Change (2015).
2. Bergquist, G. Biomass yield and soil microbial response to management of perennial intermediate wheatgrass as grain crop and carbon sink. (2019).
3. Culman, S. et al. Soil and Water Quality Rapidly Responds to the Perennial Grain Kernza Wheatgrass. Agron. J. (2013).
4. Drummond, M. A. Regional dynamics of grassland change in the western great plains. Gt. Plains Res. (2007).
5. Duchene, O. et al. Integrating multipurpose perennial grains crops in Western European farming systems. Agric. Ecosyst. Environ. (2019).
6. FAO. World food and agriculture: statistical pocketbook 2018. (2018).
7. Madejón, E., et al. Soil biochemical response to long-term conservation tillage under semi-arid Mediterranean conditions. Soil Tillage Res. (2007).
8. McKenna, T. P., et al. Community structure of soil fungi in a novel perennial crop monoculture, annual agriculture, and native prairie reconstruction. PLOS ONE (2020).
9. Melero, S. et al. Strat. ratios in a rainfed Mediterranean Vertisol in wheat under different tillage, rotation and N fertilisation rates. Soil Tillage Res.  (2012).
10. Norton, J., et al. Loss & Recovery of Soil Organic Carbon and Nitrogen in a Semiarid Agroecosystem. Soil Sci. Soc. Am. (2012).
11. Peixoto, L. et al. Decreased rhizodeposition, but increased microbial carbon stabilization with soil depth down to 3.6 m. Soil Biol. Biochem. (2020).
12. Sprunger, C. D. et al. Perennial grain crop roots and nitrogen management shape soil food webs and soil carbon dynamics. Soil Biol. Biochem. (2019).
13. Photo taken from kernza.org/what-is-kernza/
Results & Figures
Only baseline soil sampling in CRP, wheat, and fallow has occured so far. Kernza has not yet been harvested.
 
Figure 1: Higher Microbial Activity and Labile Organic Matter Near the Soil Surface under Perennials
  • Soil properties that differed significantly between farmland and CRP at at least one depth were:
    • Water stable aggregates, PMN, soil protein, total N, DOC & N, MBC & N
    • Enzymes CBH, NAG, BX, AG, SUL, and BG
  • These properties were higher in CRP at 0-5cm but lower at 5-15cm, except for PMN, which was higher in CRP at both depths
Figure 1. Four representative soil health indicators, separated by depth and field. "*" denotes significant (p<0.05) differences between horizons.
 
Figure 2: Greater Stratification between Horizons Under Perennials
  • Soil health indicators were more stratified by depth in CRP than farmland 
    • The fallow field was the most disturbed and the most similar between depths
  • Microbial biomass and enzyme activities differed most by depth (PC1)
  • NO3, DOC & N, and PHOS differed most by field (PC2)
    • These labile nutrients are highest in fallow, and may indicate increased soil disturbance
    • PHOS indicates higher phosphorus mineralization in the fallow field
Figure 2. PCA of all analyzed soil properties shows separation of plots by both depth (mainly on the x-axis) and by field (mainly on the y-axis)
 
 

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