Cover Crop Management Options to Improve Weed Control, Crop Yield and Soil Health

Progress report for LNC18-411

Project Type: Research and Education
Funds awarded in 2018: $199,820.00
Projected End Date: 10/31/2022
Grant Recipient: Kansas State University
Region: North Central
State: Kansas
Project Coordinator:
Dr. Augustine Obour
Kansas State University
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Project Information

Summary:

Cover Crop Management Options to Improve Weed Control, Crop Yield and Soil Health
Integrating cover crops (CC) into dryland crop production in the central Great Plains (CGP) can provide several benefits. These benefits include reduced soil erosion, improved nutrient cycling, suppression of herbicide­resistant (HR) weeds, enhanced crop profitability and improved soil health. Despite these benefits and growers' interest in using CC to improved soil health and suppress HR weeds, CC adoption is slow and not widely popular in the CGP because CC utilizes water that otherwise would be available to the subsequent cash crop. Grazing or haying CC can provide economic benefits to offset revenue loss associated with decreased crop yields when CC are grown ahead of a cash crop. This approach could provide an opportunity for dryland producers to build soil health and produce harvestable forage for livestock. Limited published information exists on impacts of utilizing CC for forage on weed control, soil health and crop yields in semiarid dryland (non-irrigated) systems. This research and education project will provide critical and immediate information to address producer questions on sustainable use of CC for forage while improving weed control and maintaining soil health in the region. Field experiments will be conducted on-farm and university experimental fields to investigate forage production potential, water use, weed suppression and cash crop yield penalties associated with growing CC in place of chemical fallow. Impact of CC management strategy on HR weed seed bank and population dynamics, soil organic carbon (SOC), and other soil quality parameters will be quantified. Incorporating CC into wheat-based production systems has the potential to diversify markets (particularly when grown for forage), improve HR weed control, enhance soil health and crop productivity. In addition, on-farm component of the project will be used to initiate formation of a CC producer network group for western Kansas. The group will meet annually to facilitate farmer-to-farmer learning experience and adoption of CC in the region. Increased adoption of CC by dryland producers will enhance residue cover to reduce susceptibility of farmlands to wind erosion, build and maintain soil health, and increase farm productivity. The above outcomes have potential to increase the sustainability and profitability of dryland crop production and enhance the quality of life for western Kansas producers through improved farm income, which is consistent with the broad-based outcomes of the NCR-SARE program.

Project Objectives:
  1. Determine forage production potential of cover crops in dryland systems.
  2. Quantify impacts of removing cover crops for forage on weed suppression, crop yields and soil health
  3. Conduct on-farm research to quantify the impacts of grazing cover crops on weeds, crop yields, soil health and profitability in dryland systems.
Introduction:

Dryland (non-irrigated) crop production in semiarid environments in the CGP is limited by soil water availability. Due to water limitations, winter wheat-fallow or winter wheat-summer crop (corn, grain sorghum, or sunflower)-fallow are dominant crop production systems in the region (Peterson et al., 1998; Nielsen and Vigil, 2018). The 12 to 14-month fallow period within the rotation was introduced to store soil water for the subsequent crop (Nielsen and Vigil, 2010). Fallow stabilize cash crop yields and prevent crop failure, particularly in drier years. However, precipitation storage during fallow is very inefficient, ranging from 17 to 45% in the region (Peterson and Westfall, 2004). Limited soil cover during fallow can contribute to wind erosion even in fields under long-term no-till (NT) management. This situation causes depletion in soil organic matter (SOM), declining soil fertility, soil erosion and inefficient water storage. Intensifying cropping systems in the CGP offers great potential to improve soil health, precipitation use efficiency, and enhance the productivity and profitability of dryland farming operations.

Growing CCs in place of summer-fallow has potential to improve soil health and also diversify dryland crop production in CGP. The ability of CCs to reduce wind erosion is particularly important in semiarid dryland crop production systems because residue levels are very low, predisposing fallow fields to wind erosion. Producer interest in using CC to improve soil health (improvements in SOM, water infiltration, microbial activity, and nutrient availability) have increased in the semiarid CGP regions. Grower enthusiasm of CCs and soil health in dryland NT crop production was captured in a recently held soil health workshop (http://soilhealthu.net/) organized by the High Plains Journal in Salina, KS. The topmost reasons for growing CCs among western Kansas producers are 1) improving soil health, 2) grazing opportunities for cattle, and 3) the economic cost of managing HR weeds in NT. Despite this interest, information is limited on best management options for CCs in dryland systems and producers are asking questions on best CC mixtures and planting windows for integrating CCs into cropping systems in our climate.

Several CC crop projects funded by SARE showed CC provides readily available carbon and N sources that improve soil microbial communities, accumulation of SOM and nutrient cycling (Salzer et al., 2014; Flesch, 2016; Wick et al, 2015; Narayanan et al., 2018). The increased biological activity associated with CC carbon inputs and rooting activity can improve soil aggregation and enhance water infiltration. However, most of these studies we conducted in relatively wetter regions compared to the semiarid climate of the CGP. Our research efforts in southwest Kansas showed replacing fallow with a CC increased SOM content, increase wet aggregate stability, and reduced runoff and wind erodible soil fraction (Blanco-Canqui et al., 2013). This results indicates CCs in semiarid regions can achieve soil health improvements similar to those reported in more humid regions despite limited water availability coupled with greater evaporative demand.

Cover crops in dryland crop rotations can suppress weeds and provide a significant weed management option for HR weeds in NT systems. Currently, the use of CC to suppress weeds is gaining popularity among dryland producers because of HR weeds. Eight out of ten growers attending our CC extension events expressed interest in learning more about utilizing CC to manage weeds. This is expected because repeated glyphosate applications has resulted in the development of glyphosate resistance in several weed species in dryland NT fields across Kansas. For instance, glyphosate-resistant (GR) kochia (Kochia scoparia L.), Palmer amaranth (Amarathus palmeri S. Watson), horseweed [Conyza canadensis (L.)], and Russian-thistle (Salsola tragus) biotypes have recently been reported from NT fallow production systems across the US Great Plains (Heap, 2018). The severity of these weed problems in dryland production systems of the CGP is exacerbated by the widespread occurrence of HR weed biotypes, presenting a great challenge to NT crop production in this region. Using CC to control these weeds instead of tillage would preserve the gains made in conservation tillage over the past two decades. Growing CCs will reduce herbicide application rates and frequencies (Derksen et al., 2002), decreasing weed selection pressure and the chances of weeds developing resistance to different herbicide modes of action.

Notwithstanding these benefits, CC adoption in dryland crop production in the CGP has been slow and few producers have included CCs in their production systems. A major reason is because CC utilize soil water and tend to reduce yields of subsequent crops compared to chem-fallow. Previous studies conducted in the CGP reported increase water use and decreases in wheat yields when fallow is replaced with a CC (Schlegel and Havlin, 1997; Nielson and Vigil, 2005; Holman et al, 2018). In southwest Kansas (annual precipitation of 450 mm), growing annual forage or CC during the fallow period reduced subsequent wheat yields in dry years, but had little effect on wheat yields in wet years (Holman et al, 2018). The authors reported every 125 kg ha−1 of CC or forage biomass grown, plant available water at winter wheat planting was reduced by 1 mm, which decreased the subsequent wheat crop yield by 5.5 kg ha−1. Similarly, studies in northeastern Colorado (400 mm annual precipitation) have shown a direct negative relationship between CC water use during the fallow period and the subsequent wheat yields (Nielson et al., 2015). These findings are in contrast to other studies that demonstrated growing CC had no impacts on soil water depletions and yield benefits to subsequent crops (Lenssen et al., 2013; Baxter and West, 2015; Herbert et al., 2016). This disparity is mostly due to low precipitation amounts and greater evaporative demand in the CGP region.

Developing climate-specific CC management options for dryland farmers will improve adoption and CC use in the CGP. We will investigate a flex- cropping option where CCs are grown only in years when there is adequate soil moisture or using CC for forage to reduce the negative impact of CC on cash crop yields. Flex-fallow is the concept of only planting forage or CC when soil moisture levels are adequate and the precipitation outlook is favorable. Under drought conditions, implementing flex-fallow should help minimize negative impacts in dry years. Our approach of utilizing CCs for forage (either haying or grazing) can provide economic benefits to offset revenue loss associated with decreased crop yields when CC are grown ahead of a cash crop. Our previous research showed most of the plant species planted as CC have excellent forage attributes in terms of dry matter (DM) production and forage nutritive value (Obour and Holman, 2016; Holman, et al. 2018). Due to significant regrowth potential of grass CC species, hayed or grazed CC can be allowed to regrow to provide increased residue cover compared to fallow. Opportunity exist for dual-purpose use of CCs in dryland cropping systems to provide forage and residue cover to reduce erosion and build soil health. Such cropping systems can take advantage of any additional moisture received during wet years to provide supplemental forage for the region’s livestock industry.

Producers experimenting with CCs in semiarid environments in the CGP sometimes graze CCs to maintain profitability and also justify the use of valuable soil water utilized by CC in place of chem-fallow. Very limited information regarding the effects of grazing on the soil health benefits of CC and the best practices for integrating CC in the CGP. Our study will complement recent SARE funded projects (Walker and Miller, 2016; Ragen and Benson, 2017) investigating livestock grazing of CC impacts on soil properties in Montana. Grazing CC could provide additional tool for managing HR weed populations. Many annual weeds, including kochia, are palatable and nutritious for livestock (Moyer and Hironaka,1993) and will be readily grazed with a forage CC. Grazing animals can consume HR weeds directly reducing the weed seed bank. Few studies have quantified the effect of managed CC grazing on weed communities within a cropping system, and most research has focused on grazing for weed control in regions that are warmer and wetter than the CGP (Hilimire, 2011). Results for dryland cropping systems have been mixed. For instance, integrating sheep grazing into annual hay crop-fallow-spring wheat rotation system in southwestern Montana resulted in a significant increase in weed pressure and accompanying yield reductions of 51% compared to conventional management with herbicides and tillage (Miller et al. 2015). More research is therefore needed to effectively manage weeds in these integrated crop-livestock systems, quantify grazing effects of CC on weed suppression, crop yields, and soil health in dryland systems. This producer driven project is aimed at providing critical and immediate information needed to address producer questions on when and what CC species to plant for maximum weed suppression and soil health benefits. There is also potential that grazing CC can increase soil compaction and degrade soil structure, a common constrain to grazing as an option for CCs in dryland systems. However, there is paucity of data to support this concern. It is plausible that alternate freeze and thawing events in the CGP could eliminate soil surface compaction due to CC grazing. Successful completion of this project will fill these knowledge gaps by rigorously assessing the soil health impacts of grazed and non-grazed CCs on producer fields and identify strategies for increasing the adoption of CCs as conservation practice on dryland production acreage in the CGP region.

References

Baxter, L., and C. West. 2015. SARE GS15-152.

Blanco-Canqui, H., J.D. Holman, A.J. Schlegel, J. Tatarko, and T.M. Shaver. 2013. Soil Science Society of America Journal 77:1026-1034.

Derksen, D.A., R.L. Anderson, R.E. Blackshaw, and B. Maxwell. 2002. Agronomy journal 94:174-185.

Flesch, V.D. 2016. SARE FNC16-1063.

Heap, I. 2018.  http://www.weedscience.com.

Herbert, S., W. Beiser, T. Cotter, M. Ditterson, M. Elsen, C. Hansen. 2016. SARE ONC16-015.

Hilimire, K. 2011. Journal of Sustainable Agriculture 35:376-393.

Holman, J.D., K. Arnet, J. Dille, S. Maxwell, A.K. Obour, T. Roberts, K. Roozeboom, and A. Schlegel. 2017. Crop Science 58:1–13.

Lenssen, A., S. Carlson, M. Wiedenhoeft. 2013. SARE LNC13-352.

Mailapalli, D.R., W.R. Horwath, W.W Wallender, and M. Burger. 2011. Journal of Irrigation and Drainage Engineering 138:35-42.

Miller, Z.J., F.D. Menalled, U.M. Sainju, A.W. Lenssen, P.G. Hatfield. 2015. Agronomy. Journal 107:104-112.

Moyer, J., and R. Hironaka. 1993. Canadian journal of Plant Science 73:1305-1308.

Narayanan, S., G. Zehnder, N. Tharayil, D. Millam, and C. Talley. 2018. SARE OS18-118.

Nielsen, D.C., and M.F. Vigil. 2018. Agronomy journal 110:1–8.

Nielsen, D.C., D.J. Lyon, G.W. Hergert, R.K. Higgins, F.J. Calderón, and M.F. Vigil. 2015. Agronomy journal 107: 1025-1038.

Nielsen, D.C., and M.F. Vigil. 2010. Agronomy journal 102:537-543.

Nielsen, D.C., and M.F. Vigil. 2005. Agronomy journal 97:684-689.

Obour, A.K., and J.D. Holman. 2016. ASA-CSSA-SSSA International Annual Meeting, Nov. 6 9, 2016. Phoenix, AZ. In ASA-CSSA-SSSA Abstracts 2016 [CD-ROM]. ASA, CSSA, and SSSA, Madison, WI.

Peterson, G.A, A.D. Halvorson, J.L. Havlin, O.R. Jones, D.G. Lyon, and D.L. Tanaka. 1998. Soil &Tillage Research 47:207-218.

Peterson, G.A., and D.G. Westfall. 2004. Annals of Appl. Biol. 144:127-138

Ragen, D., and T. Benson. 2017. SARE report SW17-080.

Salzer, T., A. Mach, C. Anderson, S. Peterson. 2014.  SARE FNC14-974.

Schlegel, A.J., and J.L. Havlin. 1997.  Green fallow for the central Great Plains. Agronomy journal 89:762-767.

Walker, R, and P. Miller, 2016. SARE GW16-053.

Wich, A., D. Toussaint, T. Wehlander, D. Mueller. 2015. SARE ONC15-012

Cooperators

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  • Dr. Johnathon Holman (Educator and Researcher)
  • Dr. Vipan Kumar (Researcher)
  • Dr. Monte Vandeveer (Researcher)
  • Dr. Sandy Johnson (Educator and Researcher)
  • Dr. John Jaeger

Research

Hypothesis:

Research hypotheses

  1. Integrating livestock by grazing cover crops will increase profitability of dryland crop production systems.
  2. Growing cover crops will reduce soil susceptibility to wind and water erosion, increase soil organic matter and improved soil physical properties compared to summer fallow.
  3. Utilizing cover crops for forage will not lead to sustained soil compaction due to trampling, but could lead to improved nutrient cycling and soil health compared to summer fallow systems.
  4. Growing cover crops could reduce herbicide resistant weed population in dryland crop production.
Materials and methods:
  1. On-farm research to quantify the impacts of grazing cover crops on weeds, crop yields, soil health and profitability in dryland systems

Producer cooperators and principal investigators held a meeting at Kansas State University Agricultural Research center near Hays, KS on February 7, 2019 to discuss on farm project design and cover crop specie selection. The group agreed that cover crops would planted in the fallow phase after wheat or grain sorghum in a wheat-sorghum (corn)-fallow rotation sequence. Producers had the option to plant a spring CC and grazed in the summer or plant a post-wheat CC grazing in the fall through winter.  The on-farm study compared two treatments, grazed and non-grazed CCs.

Alexander, KS: 

2019: An 80-acre field under wheat-corn-fallow cropping system was split into four replicated blocks to test grazing and non-grazed CC effects on soil properties and crop yield.  The CCs were planted into corn stubble or after wheat harvest. Spring-planted cover mixture of barley/oat/triticale/pea/sunflower/rapeseed was planted into corn stubble in April 2019. The total cover crop area was 80 acres and was split into four equal replicated strips or blocks for grazing or non-grazed. Within each strip, a 90 ft by 750 ft area was fenced and excluded from cattle grazing (non-grazed treatment) using electric wire. Each block was grazed 7-8 days with 46 heifers from 5/14/2019 to 6/14/2019 (Fig 1). A small fallow strip was included in each non-grazed plot area for weed biomass measurements. Cover crop biomass was measured by harvesting aboveground biomass within four 0.5 m2 quadrats from each block before and after grazing of the CCs. The CCs were terminated after heifers were removed from the field. Cattle weight gain was measured by weighing cattle before and after grazing using a portable livestock scale.   In addition, weed density and weed biomass (primarily kochia and field bindweed species) were measured from grazed, non-grazed treatments, and chemical fallow plot using eight 0.5 m2 quadrats after cattle were removed.  Cover crops were terminated in late June and field was planted to winter wheat in October 2019 and harvested in late-June 2020.

2020-2021: The entire filed was planted to summer cover crop mixture of sudan grass/millet/sun hemp/sunflower/radish on July 1, 2020, after winter wheat harvest.  Summer cover crops were grazed by heifers from August 7, 2020, to September 18, 2020, at a stocking rate of 575 lb/a for a total of 41 days of grazing. Before and post-grazed cover crop biomass was measured as described previously. Soil samples were collected from the plots in spring 2019 before CC planting (initial soil samples) and in spring 2021 (final soil samples), the field has had two cycles of CCs. At each sampling time, two intact soil cores of 0 to 15 cm depth were collected from each plot and split into increments of 0 to 5 cm and 5 to 15 cm.  Samples were dried at 100 °C for a minimum of 48 hours and bulk density was computed as mass of oven-dried soil divided by volume of the core. Additional soil samples were collected for each CC treatment from the 0- to 5- and 5- to 15-cm depths in ten random locations within each replicate and composited by depth. Samples were air-dried, crushed, and sieved to pass through a 2-mm stainless steel screen, and analyzed SOC and nutrient concentration. Intact soil samples were taken with a flat shovel from 0 to 5 cm and used for determination of  wet and dry aggregate stability.

Fig. 1. Cattle grazing cover crops in summer 2019 at Alexander, KS.

Hays, KS:

2019-2020:  The 50-acre field at Hays was managed under a NT winter wheat or triticale-grain sorghum-fallow rotation. In 2019, summer CC mixture of sundan grass/millet/sun hemp/sunflower/radish was planted in the first week in June into triticale stubble. Treatments were grazed CCs and non-grazed CCs, in four replicated strips. The non-grazed CC treatments were fenced using electric wire fencing materials to prevent access to cattle during CC grazing. The area of the four replicates of the non-grazed CC strips was 1.2 ha. The cattle were then given access to graze the rest of the field outside of the exclusion areas. The CC was grazed from 8/24/2019 to 10/10/2019 using 85 cow-calf pair which were turned in out groups as they calved. Cover crop biomass from the grazed and non-grazed was determined as described previously.  The CCs were frost terminated and the field planted to grain sorghum the first week in June 2020 and harvested in in October.

2020-2021: Following sorghum harvest 2020, spring CC mix of barley/oat/triticale/pea/sunflower/rapeseed was planted into the sorghum stubble in April 2021. The cover crops were grazed from 06/30/2021 to 07/20/2021 at a stocking rate of 450 lb/a.  Soil samples were taken 2019 , 2020 and  2021 as described previously to determine grazing impacts on soil properties.

Marquette, KS:

2018-2019: Two 90 acres fields were planted to CC after winter wheat harvest. The CCs comprised of triticale/radish/rapeseed and a summer mixture of sundan grass/millet/sun hemp/sunflower/radish (only in 2019). The summer CC was planted in August after volunteer wheat had been controlled whiles the fall mixture was seeded in September. The summer CC field was not grazed because of limited growth. Because of the poor performance and concerns of volunteer wheat, the farmer discontinued with the summer CC options and only fall CCs were evaluated in subsequent years at this site. The fall triticale mixture was grazed from grazed from 12/17/2018 to 02/10/2019 at a stocking rate of 550 lb/ac  by moving cattle daily. Cover crop biomass prior to grazing and after grazing were measured as described above. The non-grazed CC treatments were fenced using electric wire fencing materials to prevent access to cattle during CC grazing. The area of the four replicates of the non-grazed CC strips in Marquette was approximately 4.2 ha. Four locations within the grazed area, directly adjacent to each replicate of the fenced non-grazed CCs, were marked and used as four replicates (pseudoreplicates) for the grazed CC treatments. These pseudoreplicates were then used to determine grazing impacts on CC biomass, soil bulk density, aggregate stability and available soil nutrients.

2019-2020: A CC mixture of triticale/radish/rapeseed was planted to a different field approximately 100 acres next to the field used in 2019.  Treatment arrangement and grazing was done similar to the previous year. The CCs were grazed by yearlings (575 lb each) from 01/09/2020 to 02/17/2020 at a stocking rate of about 550 lb/ac.

2020-2021: The same CC mixture was planted to the 90-acre field used for the 2018-2019 growing season study. In 2020-2021, [heifers (560 lbs)] grazed from 1/2/2021 to 2/14/2021 at a stock rate of 550 lb/ac. Cover crop biomass before and after grazing was determined as previously described.  Soil samples were taken in 2019 and again in spring 2021 as previously described for determination of soil bulk density,  SOC, aggregate stability and available soil nutrients.

2. Research at Kansas State University experiment farms to investigate forage production potential of cover crops and quantify impacts of removing cover crops for forage on weed suppression, crop yields and soil health

This component of the project was incorporated into ongoing CC research experiments at the Kansas State University Agricultural Research Centers near Garden City and Hays, KS investigating CC management options for dryland crop production systems. The treatments were modified in the 2018-2019 growing season to evaluate grazing of spring and summer CCs including forage sorghum as a CC.  Additionally, flex-cover cropping treatment was added where CC is planted only when a minimum of 30 cm of plant available water was determined at spring planting using a Paul Brown soil moisture probe, and when the National Weather Service Seasonal Outlook for the fallow period was neutral or favorable.

a). Cover crop treatments at Southwest Research Center near Garden City, KS

    Control, Year 1: winter wheat; Year 2: grain sorghum; Year 3: fallow (common practice)

     Year 1: winter wheat; Year 2: grain sorghum; Year 3: spring cover crop hayed

     Year 1: winter wheat; Year 2: grain sorghum; Year 3: spring cover crop standing

     Year 1: winter wheat; Year 2: grain sorghum; Year 3: flex spring cover crop hayed

     Year 1: winter wheat; Year 2: grain sorghum; Year 3: flex spring cover crop standing

     Year 1: winter wheat; Year 2: grain sorghum; Year 3: 6 species cocktail mix hayed

     Year 1: winter wheat; Year 2: grain sorghum; Year 3: 6 species cocktail mix standing

     Year 1: winter wheat/forage sorghum (cover crop); Year 2: grain sorghum; Year 3: fallow

     Year 1: winter wheat/forage sorghum (hay); Year 2: grain sorghum; Year 3: fallow

*6 species mixture has included oat/triticale/barley/sunflower/rapeseed/radish

b). Cover crop treatments at Kansas State University HB-Ranch near Brownell, KS

      Control, Year 1: winter wheat; Year 2: grain sorghum; Year 3: fallow (common practice)

   Year 1: winter wheat; Year 2: grain sorghum; Year 3: spring cover crop hayed

  Year 1: winter wheat; Year 2: grain sorghum; Year 3: spring cover crop grazed

  Year 1: winter wheat; Year 2: grain sorghum; Year 3: spring cover crop standing

  Year 1: winter wheat; Year 2: grain sorghum; Year 3: flex spring cover crop hayed

  Year 1: winter wheat/summer cover crop hayed; Year 2: grain sorghum; Year 3: Fallow

  Year 1: winter wheat/summer cover crop grazed; Year 2: grain sorghum; Year 3: Fallow

  Year 1: winter wheat/summer cover crop standing; Year 2: grain sorghum; Year 3: Fallow

  Year 1: winter wheat/forage sorghum hayed; Year 2: grain sorghum; Year 3: Fallow

  Year 1: winter wheat/forage sorghum grazed; Year 2: grain sorghum; Year 3: Fallow

  Year 1: winter wheat/forage sorghum standing; Year 2: grain sorghum; Year 3: Fallow

*summer cover mixture included Sudan grass/millet/sun hemp/cowpea/radish 

Data collection 2019 to 2021

Two field experiments were established in 2018-2019 growing season at Kansas State University Agricultural Research farms near Garden City and at HB Ranch near Brownell, KS. The first experiment determined forage mass, nutritive value of spring-planted CCs and effects of dual-purpose CCs (grazing or haying CCs) on soil properties in a no-till winter wheat –grain sorghum–fallow cropping system.  This study compared spring planted CCs to fallow before winter wheat. The CCs used were a mixture of oats and triticale or cocktail mixture of oat/triticale/barley/sunflower/rapeseed/radish. The CCs were planted by the third week of March each year and terminated the first week of June.  The second study had the same objectives but compared summer planted CCs to fallow after wheat harvest but before grain sorghum in the rotation. In this study, CCs were a mixture of forage sorghum, pearl millet, sunn hemp, and cowpea at seeding rates of 7.5, 2.5, 5, and 20 lb/acre or forage sorghum at 12 lb/acre.

In both studies, CC grazing (at Brownell) and haying (Brownell and Garden City) coincided with grass crop heading. Grazed CCs were stocked with yearling heifers (weighing about 1000 lb each) at a stocking rate that remove about 30 to 40% of the available forage.

 Prior to grazing, CC biomass was sampled by taking two clippings of 0.5 m2 quadrats from each plot grazed. Fresh weights of samples were recorded, and oven dried at 50°C for at least 48 hours in a forced-air oven for DM determination.. Residue left post-grazing was determined as described above. Hayed treatments were harvested at heading to determine forage DM production and nutritive value. During each harvest, a 3-ft × 100-ft forage strip was harvested from each plot using a Carter plot forage harvester (Carter Manufacturing Company, Inc.) to a 6-inch stubble height. Whole plots samples weights were recorded, sub-samples were weighed, and oven dried for DM. Oven-dried samples from both grazing and hayed treatments were ground to pass through a 1-mm mesh screen in a Wiley Mill (Thomas Scientific, Swedesboro, NJ). The ground samples were then analyzed for forage nutritive value [crude protein (CP), acid detergent fiber (ADF), neutral detergent fiber (NDF), in vitro dry matter digestibility (IVDMD)], and tissue nutrient concentrations (Ward Laboratories, Inc., Kearney, NE) using Foss 6500 near infrared spectroscopy (NIRS).

Some regrowth of CCs following grazing before termination occurred occasionally but was usually limited in these studies. Following fallow or spring CCs, winter wheat was planted the first week of October at a seeding rate of 60 lb/ac with 7.5-inch row spacing and harvested near the last week of June using a Massey-Ferguson 8XP plot combine (Kincaid Equipment Manufacturing, Haven, KS). Eleven months after wheat harvest and following fallow or summer CCs, grain sorghum was planted near the first week of June at a rate of 35,000 seeds/ac with 15-inch row. Grain sorghum was harvested near the third week of October using the same harvesting equipment as used for wheat.

Soil sampling, analysis and crop yields 2019 to 2021

Soil samples were taken to determine bulk density and soil water content at winter wheat planting in each year. Two soil cores were collected from each plot and data averaged for a single soil bulk density or water content measurement. Soil samples were collected in 2015 at study initiation, again in the fall of 2019, 2020 and 2021 from individual plots following the termination of CCs but before subsequent winter wheat planting. Sampling in each year took place in different whole plots that represented the CC phase of the crop rotation to determine the effect on soil properties as influenced by previous crop history. Plots where CCs were produced in 2016 and 2019 were sampled for soil properties in fall 2019, plots which CCs in 2017 and 2020 were sampled in fall 2020, and plots that had CCs in 2018 and 2021 were sampled in fall 2021 . The plots sampling times represent two cycles of CCs in the WSF rotation at HB Ranch.  At each sampling time, ten soil cores (1-inch diameter) were randomly taken at 0 to 2 inches and 2 to 6 inches to determine SOC concentration. Additional three samples were collected from the 0- to 2.5 inches soil depth with a flat shovel for the determination of water stable aggregates (WSA). Winter wheat and sorghum grain yields were determined by harvesting a 5-ft × 100-ft area from the center of each plot using a small plot combine. Statistical analysis was conducted with the PROC MIXED procedure of SAS (version 9.4, SAS Inst., Cary, NC) to examine forage production, soil bulk density, SOC, and winter wheat and grain sorghum yields as a function of cover crop management options.  This report will summarize results of the forage data (2019 through 2021) and soil properties from 2019 and 2020. The 2021 soil data are will be added to the final report.

Research results and discussion:

On-farm field study

In general, the grass species in the mixture dominated CC biomass at each location. Total CC biomass after grazing at Alexander, KS, (spring planted) and Marquette, KS (fall planted) were not different from biomass measured before grazing (Table 1). Suggesting significant regrowth from the cool season CCs.  However, the post-grazed biomass was less than that of non-grazed CC in most cases. In 2019 at Hays, KS, forage mass at the time of grazing the summer CC was similar to non-grazed CC treatment because there was no regrowth between grazing and the first killing frost in October that terminated CC growth. The total forage mass of the summer CC (2019 in Hays and 2020 at Alexander) were  two –five-fold   greater than the spring or fall planted CCs. For example, spring CC biomass in 2021 at Hays averaged 1400 lb/a compared to average biomass of 6900 lb for summer CCs planted in 2019 in the same field.

Table 1. Cover crop biomass (grazed and non-grazed) at Alexander, Hays and Marquette, KS from 2019 to 2021.

Cover crop treatment

Alexander, KS

 Hays, KS

Marquette, KS

 

2019

2020

2019

2021

2019

2020

2021

 

 Cover crop biomass (lb/ac)

Pre-graze

1337 ab

3948 b

6158 a

1063 b

1262 b

955 b

2136 b

Post-grazing

 1000 b

3734 b

4744 b

429 c

1292 b

2068 a

2207 b

Non-grazed

2304 a

5189 a

6908 a

1436 a

2740 a

2653 a

3100 a

Means in a row followed by different letters indicate significant differences among cover crop management at α < 0.05

Spring CCs in Alexander, KS were grazed from May 14, 2019 to mid-June (6/14/2019) for 31 grazing days. Stocking rate was 354 lb/ac with an average daily gain of 3.1 lb/day. Similarly, summer CCs were grazed from August 7 to September 18, 2020 (41 grazing days). Stocking rate was 576 lb/ac with an average daily gain of 1.6 lb/day. Similarly, in Marquette, stocking rate averaged 550 lb/a and average daily gain was 1.2 lb/day for > 40  grazing days from 2019 through 2021 (Table 2). Grazing days and stocking rate varied at Hays because of the difference is calving time and when were turn. Notwithstanding, the lactating cows maintained their body weight by grazing on the summer CC in 2019 (Table 2).  Because of dry conditions and little forage production, cattle grazed for only 25 grazing days in 2021 at Hays.

Table 2. Grazing days and animal performance of cattle grazing cover crops in western Kansas.

Location

Starting

Ending

Class

Grazing days

Stocking rate, lb/acre

ADG

Ib/day

Avg. Wt

lb

Alexander, KS

5/14/19

6/14/19

calves

31

354

3.11

587

Alexander, KS

8/7/20

9/18/20

calves

41

576

1.6

754

Marquette, KS

12/17/18

02/10/19

Calves

54

550

1.4

560

Marquette, KS

1/9/20

2/17/20

calves

39

552

1.2

565

Marquette, KS

1/02/21

2/14/21

Calves

43

550

-

560

Hays, KS

8/24/19

10/10/19

pairs

48

274

-0.3

1246

 

9/15/19

10/10/19

pairs

25

372

-1.0

1400

 

9/28/19

10/10/19

pairs

12

403

2.7

1518

Avg Hays† (2019)

 

 

 

 28

 350

0.46

1388

Hays, KS

6/30/21

07/25/2021

Calves

25

450

-

650

†Fall calving pairs were turned out in groups as they calved.

Soil properties measured in 2019 through 2021.

At Hays and Alexander, soil bulk density, SOC, nutrient concentrations and mean weight diameter (MWD) of water stable aggregates were not different between grazed and non-graze CCs (Table 3). However, compared to the initial measurements, grazed and non-grazed CCs had significantly greater SOC and NO3-N concentration particularly at Hays.  The SOC measured in the spring 2019 at surface 0 to 2-inch depth was 1.4%, less than 2.1% SOC measured in 2021 following two cycles of grazing CCs at this location. The MWD of water stable aggregates at Hays in 2021, averaged 1.45 mm with grazed and 1.96 mm for non-grazed CCs. Similarly, at Alexander, MWD measured in 2021 was unaffected by grazing CCs (Table 3). Wind-erodible fraction was not different between CC treatments. Penetration resistance at the 0- to 6-inch soil depth with grazed CCs was not different compared to non-grazed CCs and averaged 0.52 and 0.52 MPa with grazed and non-grazed CCs, respectively.

At Marquette, measured soil properties were not different between grazed and non-grazed CCs.  Soil bulk density measured within the top 0 to 15 cm in grazed plots averaged 1.25 g/cm3 compared to 1.38 g/cm3 for the non-grazed treatment at the Marquette in 2019 (Fig. 2).  The bulk density measured on this same field in 2021 averaged 1.38 g/cm3 for grazed and 1.36 g/cm3 for the non-grazed treatment in the 0–2-inch depth.  The bulk density measured at 2–6-inch depth was 1.53 g/cm3 for grazed and 1.49 g/cm3 for non-grazed treatment.  The penetration resistance measurements 

soil bulk dednsity
Fig. 2. Effect of grazing cover crops on soil bulk density in 2019 at Marquette, KS.

taking following grazing in 2021 averaged 0.36 and 0.34 MPa with grazed and non-grazed CCs, respectively, at Marquette. The measured penetration resistance across locations and CC management strategies was below the threshold of 2 MPa that will limit root growth. The SOC concentration after two cycles of CC measured in the top 0–2-inch depth in 2021 averaged 1.74% with grazed CCs and 1.62% for non-grazed.  The SOC at 2-6 depth was unaffected by CC management and averaged 1.22 % and 0.97% for grazed and non-grazed CCs, respectively.

 

 

Table 3. Cover crop grazing effects on soil bulk density, soil organic matter, nitrate-N, phosphorus concentration, mean weight diameter (MWD) of aggregates and wind erodible fraction (WEF) measured in 2019 (initial) and 2021 at Alexander and Hays, KS

 

 

 Bulk Density

SOC

NO3-N

P

WEF

WWD

Alexander ,KS

Treatment

g/cm3

%

ppm

ppm

%

mm

0- 2 inch

Initial

1.02 b

0.98 a

1.1 b

39 a

 

1.21 a

 

Grazed

1.36 a

1.11 a

7.0 a

42 a

11.9

1.41 a

 

Non-grazed

1.36 a

1.10 a

9.7 a

34 a

14.1

1.61 a

 

 

 

 

 

 

 

 

2-6 inch

Initial

1.29 a

1.12 a

1.3 a

13 a

 

 

 

Grazed

1.41 a

1.22 a

3.6 a

8 a

11.1 a

1.05 a

 

Non-grazed

1.44 a

1.03 a

3.5 a

15 a

18.4 a

1016 a

Hays, KS

 

 

 

 

 

 

 

0-2 inch

2019 Initial

1.24 a

1.38 c

3.2 c

45.9 a

 

1.86 a

 

2020 Grazed

1.32 a

1.89 b

16.4 a

45.2 a

 

1.46 a

 

2020 non-grazed

1.2 ab

2.05 ab

14.4 a

48.3 a

 

1.96 a

 

2021 grazed

1.09 b

   2.05 a

3.6 c

53.0 a

 

 

 

2021 non-grazed

1.04 b

1.95 ab

7.5 b

48.0 a

 

 

2-6 inch

 

 

 

 

 

 

 

 

2019 Initial

1.43 a

1.35 c

1.1 c

16.2 a

 

 

 

2020 Grazed

1.41 ab

1.58 a

8.7 a

23.8 a

 

 

 

2020 non-grazed

1.38 b

1.53 ab

5.3 b

24.6 a

 

 

 

2021 grazed

1.13 c

1.52 ab

1.3 c

29.0 a

 

 

 

2021 non-grazed

1.13 c

1.39 bc

2.0 c

19.0 a

 

 

Means in a row followed by different letters indicate significant differences among cover crop management at α < 0.05.

 

K State HB Ranch

Forage production and nutritive value

Forage mass produced varied over the study period because of variations in soil water availability and air temperature in the spring.  Forages mass was greatest in 2018  and least in 2019 ( Table 4). The lower CC forage mass production in 2019 was due to wetter than normal spring conditions that delayed cover crop planting until late April. Similarly, wet soils in March 2021 delayed planting which decreased forage production. The hay treatment was harvested at a greater height (6 inches) and therefore had relatively lower yields than cover treatments (clipped at 2 inches). In 2019 and 2021 when there was time for regrowth before CC termination, biomass left after grazing was similar to that measured pre-grazing. Residue left post-grazing ranged from 69 to 84% of that biomass of the non0grazed CC treatment  across years. Therefore, careful grazing of CCs can leave adequate amount of residue to protect the soil to achieve soil health goals while providing a forage resource for livestock.

In general, grazed CC treatments had more CP, and IVDMD concentrations than CC hayed treatments. Similarly, the hayed treatment had significantly greater ADF and NDF concentrations compared to the grazed treatments (Table 4). This was expected because grazed treatments were usually sampled 7 to 10 days earlier than the hayed treatments. Delaying harvest resulted in more mature plants reducing forage digestibility and nutritive value. Nonetheless, in a production setting, grazing of forage would likely begin at a more immature stage of forage growth and the quality would match the needs of stocker cattle.

Table 4. Spring planted cover crop forage mass and nutritive content1 at heading, before grain fill over four years at the Kansas State University experiment fields at HB Ranch near Brownell, KS from 2018 to 2021.

Year

Treatment

Forage mass

CP1

ADF

NDF

IVDMD

2018

Standing

3276 a

 

 

 

 

 

Pre-grazed

3365 a

9.6 a

37 a

54 a

68 a

 

Post-grazed

2792 c

 

 

 

 

 

Hayed

3127 b

10.1 a

36 a

62 a

68 a

2019

Standing

2622 a

 

 

 

 

 

Pre-grazed

1806 c

10.8 a

31 b

53 b

83 a

 

Post-grazed

2214 b

 

 

 

 

 

Hayed

779 d

9.8  a

40 a

62 a

77 b

2020

Standing

2138 a

 

 

 

 

 

Pre-grazed

2133 a

12.6 a

34 b

60 b

78 a

 

Post-grazed

1482 b

 

 

 

 

 

Hayed

1398 b

10.5 b

41 a

68 a

69 b

2021

Standing

2454 a

 

 

 

 

 

Pre-grazed

2454 a

9.8 a

36 a

61 a

74 a

 

Post-grazed

1916 ab

 

 

 

 

 

Hayed

1435 b

9.3 a

38 a

63 a

75 a

1CP = crude protein. ADF = acid detergent fiber (higher values reflect lower digestibility). NDF = neutral detergent fiber (higher values reflect lower animal intake). IVDMD = in vitro dry matter digestibility (reflects relative energy differences).Means in a row followed by different letters indicate significant differences among cover crop management at α < 0.05.

Post-wheat summer CC forage accumulation averaged 2516 lbs/ac with substantial variation across years. A high of 3718 lbs/ac was observed in 2018 with a low of 956 lbs/ac in 2019 (Fig. 3a). Favorable conditions 2018 and 2021 supported DM production >3000 lbs/ac.  Drought conditions in 2017 and 2021 severely limited CC establishment and resulted in sparse growth, so plots were not harvested or grazed. For summer CCs, timely rainfall in July and August was critical for adequate summer CC establishment following wheat harvest. Averaged across years, hayed CCs yielded 2423 lbs of dry forage per acre (Fig. 3b). Following CC grazing, 1769 lbs of residue per acre was retained.

This indicated a 39% forage utilization rate compared to the 2905 lbs/ac available at the start of grazing. 

 

Wheat and sorghum yields

summer cover crop
Fig. 3. Summer cover crop forage accumulation across years (a) and management strategy (b) near Brownell, Kansas. Error bars indicate standard error (α =0.05) and bars with the same letter are not significantly different (α =0.05).

Spring CCs reduced wheat yields between 25 and 31% compared to fallow in two of four years with no yield differences across CC management strategies. In 2018 to 2021, wheat yield averaged 50 bu/for fallow compared to 45 bu/a for standing CCs, 44 bu/ac for grazed or 46 bu/ac with non-grazed CCs.  Summer CCs reduced grain sorghum yields up to 39% compared to fallow in one of three years only when CCs were grazed or left standing but not if CCs were hayed. Yields of wheat or grain sorghum grown more than one year following CCs in the crop rotation were unaffected by CC treatments. These results showed CCs can be grazed or hayed in NT dryland cropping systems with no negative effects on wheat and grain sorghum yields compared to standing CCs.  Grazing or haying of CCs enrolled in NRCS cost-share programs can be effective strategies to offset losses when grain yields are reduced and could potentially increase CC adoption and overall dryland cropping system profitability

Weed suppression

Alexander in 2019

In 2019, weed density was compared in chemical fallow plots with grazed and non-grazed CCs after grazing in Alexander. Data on total weed density and weed biomass (primarily kochia and field bindweed species) were collected from each plot using eight 1-m2 quadrats. Results indicated no differences in total weed biomass (40 to 48 g m-2) in grazed vs. non-grazed plots (Fig. 4). The use of herbicide in fallow plots resulted in significant reduction of total weed biomass (11 g m-2).

weed density Alexander
Fig. 4. Weed density as affected by grazing cover crops in 2019 at Alexander, KS.

HB Ranch Study in 2020 and 2021 at HB Ranch

The on-going spring-planted CC grazing study at Kansas State University HB Ranch was monitored for weed suppression in 2020 and 2021.  The treatments were oat/triticale CC which were either hayed, grazed by yearling heifers, or left standing compared to chemical fallow. Approximately four herbicide applications were made at the recommended use rate to control weeds in the chemical fallow plots. Application of dicamba with glyphosate in March, and paraquat in May. Two more sequential burndown applications of glyphosate were made in July and September to control weeds prior to winter wheat planting in October.  Weed density measurements were done in mid-June at termination of CCs. In 2020, total weed density and weed biomass (primarily glyphosate-resistant kochia) were collected from each plot using six 1-m2 quadrats before CC termination.  Results showed no differences in total weed biomass accumulation (0.8 to 1.7 g m-2) in grazed and non-grazed CC plots (Fig.

weeds at HB ranch 2020
Fig.5. Effects of cover crop management (grazing, haying, chem-fallow) on weed suppression in 2020 at KSU  HB Ranch near Brownell, KS.

5). The fallow plots had significant higher total weed biomass accumulation (140 g m-2). Dry conditions prevented weed regrowth in fallow plots after herbicide application in May 2021. Similarly, significant weed suppression from CC resulted in no measurable weed biomass in CC grazed and non-grazed at termination. 

Hays, KS  in 2021

Another spring-planted CC (spring oats/barley/spring peas mixture) study in sorghum stubble was conducted at Kansas State University Agricultural Research Center in Hays to  evaluate CC herbicide termination strategies on weed suppression. Cover crop was terminated with two different herbicide programs: (1) glyphosate only or (2) glyphosate plus soil residual herbicide (flumioxazine + pyroxasulfone) on June 26, 2021. Chemical fallow plots (where herbicides were applied to keep them weed free) were also maintained for treatment comparison. Data on total weed density and weed biomass (primarily glyphosate and dicamba-resistant kochia and Palmer amaranth) were collected from each plot using two 1-m2 quadrats at CC termination and 40 days after termination. Results showed CC treatments reduced weed biomass more than 98% compared to chem-fallow at the time of cover crop termination (Fig. 6). Furthermore, CC plots terminated with glyphosate or glyphosate plus soil residual herbicide resulted in significant weed biomass reduction at 40 days after termination in comparison to chem-fallow plots (62 g m-2) (Fig. 6). 

Weeds in Hays 2021
Fig.6. Effect of spring-planted cover crop terminated with glyphosate or glyphosate plus soil residual herbicide on weed suppression in a field at KSU Agricultural Research Center in Hays.

Soil bulk density, organic matter and aggregate stability

Grazing or haying CCs had no significant effect on bulk density from 2018 through 2021.  Averaged across the four years, fallow, non-grazed CCs, and grazed CCs had soil bulk densities of 1.11, 1.15, and 1.15 g/cm3 at the 0- to 2-inch soil depth and 1.39, 1.40, and 1.37 g/cm3 at the 2- to 6-inch soil depth, respectively. However, a significant precipitation event ( > 3 inches of rainfall) that occurred during grazing in the earlier years of the study in 2015, resulted in a significant increase in soil bulk density at 0 to 2 inch  depth . No difference in bulk density was observed beyond the top 2 inches over the study period. The SOC stocks measured in 2019 with standing and hayed CCs were greater than fallow (24.79 Mg ha-1) which was similar to grazed CCs. However, in 2020, stocks were less with hayed CCs (21.80 Mg ha-1) compared to grazed or standing CCs (24.27 Mg ha-1) and all were similar to fallow.

Mean weight diameter of water stable aggregates in the 0 to 5 cm soil depth  in 2019 and 2020 was greater with all CCs (standing, grazing, or hayed) compared to fallow (Fig. 7). Mean weight diameter was 2.79-mm for the standing CCs, 2.54-mm for the hayed CCs, 3.05-mm for the grazed CCs, and 1.78-mm for fallow. This indicates that CCs have the ability to increase soil aggregation similarly when standing, hayed, or grazed. Additionally, all CCs were found to increase the proportion of large macroaggregates (> 2-mm) compared to fallow (Fig. 8)

Fig. 8. Effects of cover crop management on aggregate size distribution measured within the 0 to 5 cm soil depth Error bars indicate standard error of the mean and bars with the same letter are not significantly different (α =0.05) within aggregates size fractions.
Fig. 7. Effects of cover crop management on mean weight diameter of water stable aggregates at HB Ranch. Error bars indicate standard error of the mean and bars with the same letter are not significantly different (α =0.05).

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Garden City, KS: 2019 to 2021 growing season

Crop data: In Garden City, forage productivity varied over the study period. Forage mass of the cocktail treatment was 1700 lb/a, 620 lb/ac and 908 lb/a in 2019, 2020 and 2021, respectively. Similarly, oat/triticale CC biomass were 2500, 617, and 1395 lb/ac in 2019, 2020, and 2021, respectively. The productivity of the flex-cover crop was like the oat/triticale treatment when it was planted in 2019 and 2020.  Post-wheat forage sorghum yields averaged 1290 lb/ac in 2019 and 2180 lb/ac in 2020.  Like HB ranch, post-wheat CC failed in 2021 growing season because of dry soil condition and limited rainfall after wheat harvest.

Wheat yields following CCs were not different from fallow in 2019. Yields averaged 90 bu/ac for fallow compared to 89 bu/ac for oat/triticale hayed or 86 bu/ac for oat/triticale standing and 91 bu/for the cocktail. Dry conditions in 2020 significantly reduced wheat yields, which averaged 23 bu/a with fallow and 19 bu/a with oat/triticale hayed or standing.

Soil samples were also collected from the Garden City study in fall 2018 and summer 2019 to examined long-term CC management effects on soil properties in a no-till (NT) winter wheat- grain sorghum-fallow cropping system in southwest Kansas. Treatments were all spring-planted and included one-, three-, and six-species CC mixtures compared with chemically controlled NT fallow. Half of each CC treatment was harvested for forage. Soil organic carbon (SOC) stocks within the 0- to 15-cm soil depth were greater with CCs compared to fallow in 2012 after three cycles of CCs in the initial wheat-fallow rotation. In 2018 and 2019 after two cycles of the WSF rotation, SOC stocks were similar across all treatments including fallow likely, because CC residue inputs declined due to a succession of drought years. The significant residue contribution from grain sorghum in the WSF rotation increased SOC in 2018 and 2019 in all treatments compared to 2012. Soil aggregation was greater with CCs compared to the fallow treatment and was unaffected by CC diversity. Mean weight diameter (MWD) of water stable aggregates was 1.11 mm with standing CCs compared with 0.77 mm for pea.  The MWD of dry aggregates with standing (3.55 mm) and hayed CCs (3.62 mm) were greater compared to fallow (2.75 mm). Water infiltration rates and saturated infiltrability measured in summer 2019 were greater with CCs compared. These findings suggest simple CC mixtures and CCs managed for annual forage provide similar soil benefits as diverse CCs mixtures and CCs left standing.

 

 

Participation Summary
3 Farmers participating in research

Project Activities

Dryland Soil Health Network Meeting
Field day at producer field near Marquette, KS

Educational & Outreach Activities

15 Consultations
11 Curricula, factsheets or educational tools
10 Journal articles
3 On-farm demonstrations
1 Online trainings
4 Tours
20 Webinars / talks / presentations
5 Workshop field days
11 Other educational activities: Radio interviews (5)

Participation Summary:

450 Farmers participated
80 Ag professionals participated
Education/outreach description:

Journal articles

  1. Homan, J.D., A. Schlegel, A.K. Obour, and Y. Assefa. 2020. Dryland cropping system impact on forage accumulation, nutritive value, and rainfall use efficiency. Crop Science.2020;1–15. https://doi.org/10.1002/csc2.20251.
  2. Holman, J.D., Y. Assefa, and A.K. Obour.2020. Cover Crop Water Use and Productivity in the High Plains Wheat-Fallow Crop Rotation. Crop Science https://doi.org/10.1002/csc2.20365
  3. Kumar, V., A. Obour, P. Jha, R. Liu, M. R. Manuchehri, J. A. Dille, J. Holman7, and P. W. Stahlman. 2020. Integrating cover crops for weed management in the semi-arid U.S. Great Plains: opportunities and challenges. Weed Sci. 68: 311-323.  DOI: 10.1017/wsc.2020.29.
  4. Obour, A.K., J. D. Holman, and A.J. Schlegel. 2020. Spring triticale forage responses to seeding rate and nitrogen application. Agrosyst. Geosci.  Environ. 3:e20053. https://doi.org/10.1002/agg2.20053
  5. Blanco-Canqui, H., S.J. Ruis, J. Holman, C. Creek, A. K. Obour. 2021. Can cover crops improve soil ecosystem services in water‐limited environments? A review. Soil Sci. Soc. Am. J. https://doi.org/10.1002/saj2.20335
  6. Holman, J., A. Obour, Y. Assefa. 2021. Productivity and profitability with fallow replacement forage, grain, and cover crops in W‐S‐F rotation. Crop Sci. https://doi.org/10.1002/csc2.20670
  7. Holman, J., A. Obour, Y. Assefa. 2021. Fallow replacement cover crops in a semi-arid High Plains cropping system. Crop Sci. 61:3799-3814. https://doi.org/10.1002/csc2.20543
  8. Obour, A.K.,  L.M. Simon, J.D. Holman, P.M. Carr, M. Schipanski, S. Fonte, R. Ghimire, T. Nleya  & H. Blanco-Canqui. 2021. Cover crops to improve soil health in the north American Great Plains. Agron. J. http://dx.doi.org/10.1002/agj2.20855
  9. Simon, L.M. K. Obour, J. D. Holman, and K. L. Roozeboom. 2022. Long-term cover crop management effects on soil properties in dryland cropping systems. Agric. Ecosyst. Environ. 328, 107852 https://doi.org/10.1016/j.agee.2022.107852
  10. Simon, L.M, K. Obour, J.D. Holman, S.K. Johnson and K. L. Roozeboom. 2021. Forage productivity and soil properties in dual‐purpose cover crop systems. Agron. J. http://dx.doi.org/10.1002/agj2.20877.
  11.  

Presentations

  1. Holman, J., and A. Obour. 2019. Cover crop use in a semi-arid wheat-sorghum-fallow cropping system. ASA-CSSA-SSSA International Annual Meeting, Nov. 11-14, 2019. San Antonio, TX. In ASA-CSSA-SSSA Abstracts 2019 [CD-ROM]. ASA, CSSA, and SSSA, Madison, WI.
  2. Simon, L., A.K. Obour, J.D. Holman, K.L. Rooseboom. 2019. Long-term cover crop effects on soil organic carbon, nitrogen stocks, and water stable aggregates in the semiarid central Great Plains. ASA-CSSA International Annual Meeting, San Antonio, TX, Nov. 10-13, 2019. In ASA-CSSA-SSSA Abstracts 2019 [CD-ROM]. ASA, CSSA, and SSSA, Madison, WI.
  3. Obour, A.K., J.D. Holman and L. Simon. 2020. Dual use of cover crops for forage and soil health in dryland cropping systems. Women Managing farms conference, Fe.13-14, 2020, Manhattan, KS.
  4. De Jesus, D.M., A.K. Obour, V. Acosta-Martinez, J. Holman, and M. Vandeveer. 2019. Soil microbial community response to long-term cover crop use in dryland systems of the central Great Plains. ASA-CSSA International Annual Meeting, San Antonio, TX, Nov. 10-13, 2019. In ASA-CSSA-SSSA Abstracts 2019 [CD-ROM]. ASA, CSSA, and SSSA, Madison, WI.
  5. Obour, A.K., J.D. Holman and Sandy Johnson. Annual forage fertility management and soil health. Southwest Kansas Forage Conference. Feb. 27, 2020, Garden City, KS.
  6. Obour, A.K., J.D. Holman, L. M. Simon and S. Johnson. 2020. Dual use of cover crops for forage and soil health in dryland systems. ASA-CSSA-SSSA International Annual Meeting, Virtual, Nov. 9-13, 2020. In ASA-CSSA-SSSA Abstracts 2020 [CD-ROM]. ASA, CSSA, and SSSA, Madison, WI.

  7. Simon, M. L., A. K. Obour, J. D. Holman, K. L. Roozeboom. 2020. Dual-purpose cover crops for soil health and forage production in the semiarid central Great Plains. ASA-CSSA-SSSA International Annual Meeting, Virtual, Nov. 9-13, 2020. In ASA-CSSA-SSSA Abstracts 2020 [CD-ROM]. ASA, CSSA, and SSSA, Madison, WI.
  8. Holman, J.D., K. Obour, L. Simon, A.J. Schlegel. 2020. Long-term forage rotation yields, soil water use, and profitability. In Proc. of the Great Plains Soil Fertility Conf., 2020. Vol. 18:158-164.
  9. Simon, L.M., K. Obour, J.D. Holman, K.L. Roozeboom. 2020. Long-term cover crop and annual forage effects on soil organic carbon, nitrogen stocks, and water stable aggregates in the semiarid central Great Plains. In Proc. of the Great Plains Soil Fertility Conf., 2020. Vol. 18:203-207.
  10. Obour, A. K., Simon, L. M., Holman, J. D., & Johnson, S. K. (2021) Effects of grazing cover crops on soil properties in no-till rain-fed cropping systems in west central Kansas [Abstract]. ASA, CSSA, SSSA International Annual Meeting, Salt Lake City, UT. https://scisoc.confex.com/scisoc/2021am/meetingapp.cgi/Paper/133324
  11. Simon, L. M., Obour, A. K., Holman, J. D., Schipanski, M. E., Johnson, S. K., & Roozeboom, K. L. (2021) Post-wheat summer cover crop effects crop yields and soil properties in a no-till dryland cropping system [Abstract]. ASA, CSSA, SSSA International Annual Meeting, Salt Lake City, UT. https://scisoc.confex.com/scisoc/2021am/meetingapp.cgi/Paper/134639.
  12. Obour, A.K. J. D. Holman, & L. Simon. 2021. Cover crops to improve soil health in dryland systems. Invited Guest Lecture, Fort Hays State University, Hays, KS, October 4, 2021
  13. Obour, A.K. J. D. Holman, & L. Simon. 2021. Cover crop management options to improve soil health in dryland systems. Bottom Line Conference, Lakin, KS, August 25-26, 2021
  14. Obour, A.K., J. D. Holman, & L. Simon. 2021. Western Kansas cover crop research update. Kansas Soil Partnership Monthly Meeting, Virtual, April 28, 2021.
  15. Obour, A.K, J.D. Holman, L. Simon and S. Johnson. Dryland Cover Crops Grazing Research in Western Kansas. Northwest Agronomy Update, Ness City, KS. December 7, 2021.
  16. Obour, A.K, J.D. Holman, L. Simon and S. Johnson. Dryland cover crop grazing research in western Kansas. Cattle Conversations, Virtual, December 23, 2021.
  17. Obour, A.K. J. D. Holman, & L. Simon. 2021. Cover crop grazing research in western Kansas. Tear Down the Walls Meeting, Fort Collins, CO. August 16-17, 2021.
  18. Obour, A.K. J. D. Holman, & L. Simon. 2021. Cover crop options for dryland systems. Tailgate Talk and Field day. Russell County, KS. July 28, 2021
  19. Obour, A.K. J. D. Holman, & L. Simon. 2021. Cover crops to improve soil health in dryland systems. Producer Meeting, Hay, KS. Nov 18, 2021.
  20. Obour, A.K. J. D. Holman, & L. Simon. 2021. Cover crops to improve soil health in dryland systems. Producer Meetings, Norton, KS. December 6, 2021.
  21.  

Workshop and field days

  1. Organized Dryland Soil Health Network Kickoff Meeting at Hays, KS on Feb. 18, 2020. There were 30 participants (farmers, Ag retailers, NRCS Staff and K-State Research and extension faculty) at the meeting. Overall goal of the dryland soil health initiative is to advance soil management strategies to improve soil health and crop productivity of dryland cropping systems through participatory research learning.
  2. Obour, A.K. 2020. Dual use of cover crops for forage and soil health in dryland cropping systems. Western Kansas Agricultural Research Center Virtual Field Day, Aug. 26, 2020.
  3. Holman, J.D. 2020. A decade of dryland cover crop research in western Kansas. Western Kansas Agricultural Research Center Virtual Field Day, Aug. 27, 2020.
  4. Organized a cover crop field day with collaborator producer near Marquette, KS on August 24, 2021. Topic covered included using cover crops for grazing; management options for soil health; cover crops and water quality, and NRCS cover crop programs (45 farmer attendees)
  5. Organized cover crop field day on producer field on May 25, 2021 at Hays Kansas. Topic covered included using cover crops for grazing; management options for soil health; cover crops and water quality, and NRCS cover crop programs (45 farmer attendees)

Extension and Proceedings publications

  1. Simon, L.M., A.K. Obour, J.D. Holman, K.L. Roozeboom. 2020. Long-Term Cover Crop and Annual Forage Effects on Soil Organic Carbon, Nitrogen Stocks, and Water Stable Aggregates in the Semiarid Central Great Plains. In of the Great Plains Soil Fertility Conf., 2020. Vol. 18:203-207.
  2. Obour, A. K., J. D. Holman, J. A. Dille, and V. Kumar. 2019. Effects of spring-planted cover crops on weed suppression and winter wheat grain yield in western Kansas. Kansas Agricultural Experiment Station Research Reports: Vol. 5: Iss. 6. https://doi.org/10.4148/2378-5977.7784.
  3. Obour, A. K., J.D. Holman, and J. R. Jaeger. 2019. Cover crop management effects on soil water content and winter wheat yield in dryland systems. Kansas Agricultural Experiment Station Research Reports: Vol. 5: Iss. 6. https://doi.org/10.4148/2378-5977.7785.
  4. Simon, L.M., A.K. Obour, J.D. Holman, K.L. Roozeboom. 2020. Long-term cover crop and annual forage effects on soil organic carbon, nitrogen stocks, and water stable aggregates in the semiarid central Great Plains. In Proc. of the Great Plains Soil Fertility Conf., 2020. Vol. 18:203-207.
  5. Johnson, S., J. Brummer, A. Obour, A. Moore, J. Holman, and M. Schipanski. 2020. Cover crop grown post-wheat for forage under dryland conditions in the High Plains.  Kansas State Univ. Agric. Expt. Station & Coop. Ext. Publication no. MF3523.  https://bookstore.ksre.ksu.edu/pubs/MF3523.pdf.
  6. Simon, L. M. A.K. Obour, J. D. Holman, and K. L. Roozeboom. 2020. Long-Term Cover Crop Management Effects on Soil Health in Semiarid Dryland Cropping Systems, Kansas Agricultural Experiment Station Research Reports: Vol. 6: Iss. 5. https://doi.org/10.4148/2378-5977.7927.
  7. Obour, A. K.; Holman, J. D.; Simon, L. M.; and Johnson, S. K. 2020. Dual use of cover crops for forage production and soil health in dryland crop production. Kansas Agricultural Experiment Station Research Reports: Vol. 6: Iss. 5. https://doi.org/10.4148/2378-5977.7930.
  8. Simon, L. M., A. K. Obour, J. D. Holman, S. K. Johnson, and K. L. Roozeboom, K. 2021. Forage accumulation of spring and Summer cover crops in western Kansas. Kansas Agricultural Experiment Station Research Reports: Vol. 7: Iss. 5. https://doi.org/10.4148/2378-5977.8134
  9. Simon, L. M.; A. K. Obour, J. D.  Holman, S. K. Johnson, and K.L. Roozeboom. 2021. Dual-Purpose cover crop effects on soil health in western Kansas no-till dryland cropping. Kansas Agricultural Experiment Station Research Reports: Vol. 7: Iss. 5. https://doi.org/10.4148/2378-5977.8135
  10. Obour, A.K., L. Simon, J. Holman & Sandy Johnson. 2021. Does grazing cover crops impact soil properties? Agronomy eUpdate, Issue 868 Agronomy eUpdate August 12th, 2021 : Issue 868 (ksu.edu).
  11. Obour, A. K., L.M. Simon, J. D.  Holman and S. K. Johnson. 2021. Does grazing cover crops impact soil properties? Kansas Agricultural Experiment Station Research Reports: Vol. 7: Iss. 5. https://doi.org/10.4148/2378-5977.8078
  12.  

Radio Interviews

  1. Grazing cover crops and soil health with K-State Agricultural Today on Feb. 13, 2020 in Manhattan, KS.
  2. Dryland soil health initiative with Eagle Radio on Feb. 14, 2020 in Hays, KS.
  3. No-till magazine: Cover crop as fallow alternative in dryland systems. 07/19/2021.
  4. K-State Agriculture today: soil properties in dual-purpose cover crop systems. 08/09/2021.
  5. Harvest Public Media: Cover crops in dryland environments. 08/12/21.
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.