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

Click linked name(s) to expand
  • 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 CCs would be planted in the fallow phase after wheat or grain sorghum in a wheat-sorghum-fallow rotation sequence. Producers had the option to start with a spring-planted CC and grazed in the summer or a post-wheat CC with grazing in the fall through winter.

Alexander, KS: Spring CC 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. Within each strip, a 90 ft by 750 ft area was fenced and excluded from cattle grazing using electric wire. Each block was grazed 7-8 days with 31 heifers from 5/14/2019 to 6/14/2019 (Fig.1). The field was planted to winter wheat in October 2020. Following winter wheat harvest in mid-June, the entire filed was seeded back to summer cover crop mixture of sudan grass/millet/sun hemp/sunflower/radish on July 1, 2020.  Summer cover crops were grazed by heifers from August 7, 2020 to September 18, 2020 for a total of 41 days of grazing.

Fig. 1. Cattle grazing cover crops in Alexander, KS.

Hays, KS: Summer CC mixture of Sudan grass/millet/sun hemp/sunflower/radish was planted the first week in June after winter triticale harvest. The CC was grazed from 8/24/209 to 10/10/2019 using 85 cow-calf pair which were turned in out groups as they calved. Marquette, KS: Two 90 acres fields were planted to CC after winter wheat harvest. The CCs comprised of triticale/radish/rapeseed (in 2018 and 2019) and a summer mixture of Sudan 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. The triticale mixture was grazed in the winter from December through February.

Cover crop biomass at each location was measured by harvesting biomass within four 5.4 ft2 quadrats from each block before and after grazing of CCs. The CCs were terminated after heifers will removed from the field. Cattle weight gain was measured by weighing cattle before and after grazing using a portable livestock scale. Soil samples were taken at 1 ft increments to 5 ft to determine soil water content at winter wheat planting. Two soil cores were collected from each block and data averaged for a single soil bulk density or water content measurement. Additional soil samples were taken at 0 to 5 cm and 5 to 15 cm after CC termination to determine SOC concentration, pH, potentially mineralizable N (PMN), particulate organic carbon (POXC), available N and P concentration.

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.

  1. 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

  1. 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 up to date:

Cover crop biomass was sampled by taking two clippings of 5.4 ft2 quadrats from each plot before and after grazing. 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. The plots were then mob grazed using a stocking density that utilized approximately 30 to 40% of the available forage mass at the time of grazing. Residue left post-grazing was determined as described above. Hayed treatments were harvested at heading by harvesting a 3-ft × 100-ft forage strip from each plot using a Carter plot 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).

Soil samples were taken to determine bulk density and soil water content at winter wheat planting. Two soil cores were collected from each plot and data averaged for a single soil bulk density or water content measurement. In 2019, soil samples were taken at 0 to 2 inches and 2 to 6 inches after CC termination to determine SOC concentration. 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

Research results and discussion:

On-farm field study

In general, grass specie in the mixture dominated CC biomass at each location. Total CC biomass after grazing at Alexander, KS, (spring planted) and Marquette, KS (fall planted) was greater than biomass measured before grazing (Figure 2). However, the post-grazed biomass was less than that of ungrazed CC. In Hays, KS, forage mass at grazing was similar to ungrazed CC treatment because there was no regrowth between grazing and when CC growth was terminated by frost. The total forage mass of the summer CC was five-fold greater than the spring or fall planted CCs (Fig. 2). For example, spring CC biomass in 2019 averaged 600 lb/a compared to average biomass of 3900 lb for summer CCs planted in 2020 in the same location.

Fig. 2. Cover crop forage mass measured in 2019 at Alexander, KS (spring-planted), Marquette, KS (fall-planted), and Hays, KS (summer-planted ).

The total grazing days of CCs varied across study locations. 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. Furthermore, 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, there was 39 grazing days in Marquette with ADG of 1.2 lb/day. Grazing days and stocking rate varied at Hays because of the difference is calving time and when cow-calf pairs were turnout to graze. Notwithstanding, the lactating cows maintained their body weight by grazing summer CCs at Hays (Table 1). 

Table 1. 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

1/9/20

2/17/20

calves

39

552

1.2

565

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†

 

 

 

 28

 350

0.46

1388

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

Soil bulk density measured after grazing CCs was not different compared to the ungrazed treatments. For example, soil bulk within the top 0 to 15 cm  in grazed plots averaged 1.25 g cm3 compared to 1.38 g cm3 for the ungrazed treatment at Marquette in 2019 (Fig. 3).

Across sites, soil bulk density, aggregate size distribution, and mean weight diameter (MWD) of water stable aggregates were not different between grazed and non-graze CCs (Table 2). However, the MWD measured under two perennial pastures near the field sites averaged 3.70 mm, approximately 2.9-fold greater than MWD with grazed (1.26 mm) or non-grazed CCs (1.28 mm). Soil pH and SOC did not differ between the grazed and non-grazed CCs but both were significantly less than that under pasture. Soil nitrate, phosphorus, iron, manganese, and copper concentrations with grazed or non-grazed CCs were significantly greater (P > 0.05) than in pasture (Table 2).

Table 2. Soil physical and chemical properties in the 0- to 15-cm soil depth as influenced by cover crop management: no-till grain-based cropping systems with grazed cover crops or non-grazed cover crops and perennial pasture.

Soil property

Cover crop management

Grazed cover crops

Non-grazed over crops

Pasture

pH

5.62  b+  

5.76 b

6.71a

Bulk density (g cm-3)

1.35a

1.31 a

1.2b

Total N (g kg-1)

1.5 c

1.7 b

2.3 a

SOC (g kg-1)

15.5 b

17.0 b

23.6 a

NO3-N (mg kg-1)

7.1 a

6.1 a

1.1 b

NH4-N (mg kg-1)

13.8 a

18.0 a

11.4 a

P (mg kg-1)

48.2 a

46.6 a

13.4 b

Zn (mg kg-1)

0.79 a

0.95a

1.18 a

Fe (mg kg-1)

56.8 a

53.3  a

33.4 b

Mn (mg kg-1)

60.8  a

58.4 a

37.9 b

Cu (mg kg-1)

1.3 a

1.3 a

1.0 b

MWD (mm)

1.26 b

1.28 b

3.70 a

 

Fig.3. Effect of grazing cover crops on soil bulk density in Marquette,KS.

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 2015 (3145 lb/a) and least in 2019 (1655 lb/a, Figure 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, a cold and dry spring in 2016 resulted in less CC productivity. In years with limited regrowth (2016, 2017 and 2018), CC forage mass at the time of grazing was similar to ungrazed (cover) CC treatment. 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 2015 and 2019 when there was time for regrowth before CC termination, biomass left after grazing was similar to that measured pregrazing. Across years, CC residue post-grazing averaged 68% of that at pregrazing. 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.

Fig. 4. Forage mass of spring-planted cover crops at Kansas State University HB-Ranch near Brownell, KS.

Forage CP, IVDMD and mineral concentrations were greater in years when CCs were harvested early at heading (2015, 2017 and 2019) than when CCs were more mature (2016 and 2018) (Table 3). In general, grazed CC treatments had more CP, nutrients (Ca, P, K) and IVDMD concentrations than CC hayed treatments. Similarly, the hayed treatment had significantly greater ADF and NDF concentrations compared to the grazed treatments (Table 3). 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 3. Cover crop forage mass and nutritive content1 at heading, before grain fill over 5 years at the Kansas State University experiment fields at HB Ranch near Brownell, KS

Year

CP

ADF

NDF

IVDMD

Ca‡

P

K

 

                                                     %

2015

19.1 a§

33.7 c

53.8 c

84.9 a

0.77 a

0.41 a

3.13 a

2016

8.6 d

39.9 a

66.5 a

66.0 b

0.31 c

0.25 d

2.07 c

2017

11.7 b

34.5 bc

62.7 ab

73.0 b

0.46 b

0.29 bc

2.13 bc

2018

9.9 cd

36.4 b

58.1  bc

68.2 b

0.35 c

0.27 cd

2.32 bc

2019

10.3 c

35.8 b

57.1 bc

80.1 a

0.37 c

0.30 b

2.33 b

Cover crop

                                             %

Grazed

12.9 a

34.2 b

56.2 b

76.6  a

0.51 a

0.31 a

2.43 a

Hayed

11.0 b

37.9 a

63.0  a

72.4  b

0.39 b

0.29 b

2.37 a

CP = 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), Ca; calcium; P; phosphorus; K; potassium.

§Values within a column followed by the same letter (s) are not significantly different (P < 0.05).

Post-wheat summer CC forage accumulation averaged 2516 lbs/ac with substantial variation across years (coefficient of variation = 53.17). A high of 3718 lbs/ac was observed in 2018 with a low of 956 lbs/ac in 2019 (Fig. 5a). Drought conditions in 2017 severely limited CC establishment and resulted in no harvestable yield. Favorable conditions in 2016 and 2018 supported DM production >3000 lbs/ac. In this study, 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. 5b). 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.

Fig. 5. 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).

Soil bulk density and organic matter

Except in 2015, growing a CC had no effect on soil bulk density measured at 0 to 2 inches at winter wheat planting. Grazing a CC in 2015 resulted in a significant increase in soil bulk density at 0 to 2 inches (Figure 6a).

Fig. 6. Cover crop management effect on soil bulk density (a) measured from fall 2015 to 2018 and soil organic carbon (b) measured in 2019 at the Kansas State University experiment fields at HB Ranch near Brownell, KS. Bars followed by the same letter (s) are not significantly different (P < 0.05).

This was because of a significant precipitation event ( > 3 inches of rainfall) that occurred during grazing. No difference in bulk density was observed beyond the top 2 inches over the study period. The SOC concentration measured in 2019 was not different due to treatments at the surface 0 to 2 inch soil depth. However, the CC treatments did increase SOC concentration within 2 to 6 inch depth (Figure 6b) compared to fallow. The SOC concentration with haying or grazing CCs was similar to that of the true cover treatment, suggesting belowground biomass from CC roots contributes to SOC storage. These results showed CCs could be utilized for forage with minimal impacts on SOC.

Mean weight diameter of water stable aggregates in the 0 to 5 cm soil depth 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

This study examined long-term CC management effects on soil properties in a no-till (NT) winter wheat (Triticum aestivum L.)-grain sorghum (Sorghum bicolor Moench)-fallow (WSF) cropping system in southwest Kansas. Treatments were all spring-planted and included peas (Pisum sativum L.) for grain as well as 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 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 in all treatments compared to 2012. Soil aggregation was greater with CCs compared to peas or fallow 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 were greater with CCs compared to peas. 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

Educational & Outreach Activities

5 Curricula, factsheets or educational tools
4 Journal articles
3 On-farm demonstrations
1 Online trainings
4 Webinars / talks / presentations
3 Workshop field days

Participation Summary

130 Farmers
75 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

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.

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.

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.

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.
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.