A system for producing corn in a living mulch of kura clover has been developed and tested in Wisconsin. We determined that grain or silage yields were not increased by addition of N fertilizer to corn growing in kura clover living mulch that had been suppressed by herbicides. Zone tillage was an effective substitute for herbicidal killing of kura clover in the corn row, but mechanical suppression (mowing) of kura clover in the inter-row area resulted in yield loss compared to inter-row clover suppression with herbicides. Corn grown in a zone tilled kura clover field, with inter-row clover suppressed by glyphosate, and no N fertilizer, produced similar grain and silage yields as conventional corn production.
Alfalfa-corn rotations occupy approximately 6 million acres of Wisconsin cropland (Wisconsin Dep. of Agriculture, Trade, and Consumer Protection, 1997). This rotation evolved as a means to meet feed requirements of livestock, as a cheap way to meet N requirements for corn production, and as a means to conserve soil on hilly landscapes. Conservation tillage systems (i.e., where residue provides at least 30% ground cover) in these rotations lower the risk for soil erosion, particularly during crop establishment (Wollenhaupt et al., 1995); yet, as recently as 1995, only 14.5% of Wisconsin’s 4 million acres of forages were established using such systems (Conservation Technology Information Center, 1995). Tillage incorporates beneficial crop residue and exposes soil aggregates to direct impact from rainfall. Crop residue and living plants reduce soil erosion in the rotation by intercepting rainfall and limiting sediment detachment, surface sealing, and sediment transport in runoff (Gallagher et al., 1996; Wollenhaupt et al., 1995; Zemenchik et al., 1996). Zemenchik et al. (1997) illustrated that once alfalfa is established, the risk for soil erosion is much less than at any other time during the rotation. Extending the soil-conserving characteristics of established perennial forages throughout a crop rotation with corn would greatly improve soil conservation.
Living mulches are plants intercropped with a cash crop that can decrease erosion (Wall et al., 1991), suppress weeds (Enache and Ilnicki, 1990), reduce insect pests (Litsinger and Moody, 1976), and in the case of legumes, supply N (Scott et al., 1987). Corn yields in such systems can by equal to or greater than those in conventional corn production systems in regions where seasonal precipitation in typically high and uniformly distributed, such as in the north central USA (Zemenchik et al. 2000; Affeldt et al. 2004).
Kura clover is a long-lived, perennial, rhizomatous legume (Bryant, 1974) that tolerates frequent defoliation in monoculture (Peterson et al., 1994) or in binary mixture with grass (Kim, 1996) and is suitable for hay or pasture production in the north central region of the USA (Sheaffer et al., 1992). Kura clover is adapted to long, cold winters (Sheaffer and Marten, 1991) and has persisted for greater that 20 years.
Characteristics of kura clover made it an outstanding candidate for evaluation as a living mulch for corn production. Based on earlier research in our laboratory, we concluded that corn can be produced in this type of system if kura clover is adequately suppressed with herbicides, but yields were not consistent (Zemenchik et al. 2000). While kura clover recoveres from suppression, cool temperatures after sowing can delay corn development, resulting in reduced corn stands and yield. That research demonstrated that for the kura clover living mulch to be consistently useful for corn production, there needs to be a combination of killing or severely disrupting kura clover in the corn row, suppression of kura in the inter-row area, and ability to control both recovering kura and germinating annual weeds 30 to 40 days after sowing.
Our current research incorporates a band kill plus broadcast suppression of kura clover and has employed herbicide resistant corn technology to provide flexibility in control of both kura clover and annual or perennial weeds after corn emergence. Affeldt et al. (2004) reported that broadcast suppression of kura clover with a low rate of Round-up, band killing an 8-inch strip over the corn row just after planting, and use of either Round-up Ready or Liberty Link corn hybrids with partner herbicides applied 30 days after sowing provided consistent results over four environments. Recovery of kura clover after 1999 corn production at Arlington, measured in spring 2000, was about 80% of control plots in mid-May and 100% of control plots in mid-June.
The kura clover living mulch system for corn production is ready to be tested at the on-farm level. Quantification of N credits will give farmers information necessary for making a decision about the utility of learning how to grow corn in a living mulch and changing their production practices. Although the kura clover living mulch system utilizes minimal and relatively environmentally safe herbicides, we think it necessary to explore options to substitute some or all herbicide with mechanical suppression of kura. Furthermore, zone-tillage has been shown to provide earlier soil warming and improved yield compared to strict no-till corn production (Cox et al., 1990). Our project aimed to address these issues.
- To determine if mechanical suppression can replace herbicide suppression of kura clover in the corn row and inter-row area.
To determine the N fertilizer replacement value of kura clover living mulch.
To determine and overcome limitations to farm-scale use of the kura clover living mulch system.
Replacement of Chemical Band Killing by Zone Tillage of Kura Clover:
Field studies were conducted at the University of Wisconsin Agricultural Research Stations in Arlington and Lancaster, WI in 2001, 2002 and 2003. Kura clover, cv. Endura, was established in 1996 at Lancaster and in 1997 at Arlington. Plants were well nodulated as a result of seed inoculation with rhizobia before planting. Kura clover was regularly mowed and harvested in the years before starting the experiments. Fertilizer P and K were applied to kura clover at both locations based on soil test recommendations for alfalfa.
For all the treatments, kura clover was suppressed with a broadcast application of glyphosate plus dicamba before planting the corn. Then, a combination of herbicidal and mechanical treatments were applied as follows: 1) control: kura clover was killed with a broadcast application of glyphosate plus flumetsulam and clopyralid at planting time in 2001 and 2002 and 15 days before corn planting in 2003; 2) zone-tilled: a 20-cm band was zone-tilled with a rototiller 10 days before planting; 3) band-killed: a 20-cm band was killed with flumetsulam and clopyralid; and 4) suppressed only. A second application of glyphosate was made to all plots to control annual weeds and recovering kura clover at the corn V3 to V5 stage 30 to 40 days after corn planting.
Glyphosate resistant corn was no-till planted on 9 May 2001, 30 April 2002 and 13 May 2003 at both locations. Corn was sown in 76-cm spaced rows at 79,000 plants/ha using a 4-row Kinze PT planter at Arlington and at 78,800 plants/ha using a 4-row White 6104 air planter at Lancaster. A starter fertilizer (6-24-24) was applied at 68 kg/ha of product, totaling 9.9, 7.7 and 14.4 kg/ha of N, P and K, respectively. To prevent N limitation in the experiment, 56 kg/ha of side-dressed N was applied as ammonium nitrate to all plots at the V4 to V5 corn stage.
Plot size was 3.0 by 9.1 m. Each plot had four corn rows, where one of each of the center rows was harvested for grain or whole-plant yield determination and the outside two were border rows. Outside the experimental area, four corn rows were planted as border. The four treatments in each experiment were arranged in a randomized complete block design with four replications.
Soil temperature was measured at a 5-cm depth in all treatments, using a manual field thermometer that was randomly inserted along the planting line of the two center rows of each plot. Two readings per plot were taken starting on the planting date and continuing for three weeks after. Early seedling development was monitored to determine if the mechanical and herbicide suppressions had a different impact on corn development. Stand counts were made at whole-plant or grain harvest. Developmental stage of plants was recorded from V2 to V8 to determine differences in plant growth among treatments.
Corn whole-plant dry matter yield was determined at the 50% kernel milk line stage. From one of the two internal rows of the four-row plots, 7.6 m were harvested from the plot center by hand. Plants were cut leaving a 20-cm stubble and chopped to a 2- to 5-cm particle size using a commercially available corn silage chopper. Sub-samples were dried at 60 C to calculate dry matter content to adjust corn whole plant yields to a dry matter basis. Grain yield was determined by harvesting 7.6 m of row from the other internal row after physiological maturity. Ears were hand-collected and passed through a stationary sheller. Corn grain yields were adjusted to a moisture concentration of 155 g/kg.
Kura Clover Mulch as a Nitrogen Source:
Field studies were conducted at University of Wisconsin Agricultural Research Stations in Arlington and Lancaster, WI in 2001, 2002 and 2003. Kura clover, cv. Endura, was established in 1996 at Lancaster and in 1997 at Arlington. Plants were well nodulated as a result of seed inoculation with rhizobia before planting. Kura clover was regularly harvested in the years before starting the experiments. Fertilizer P and K were applied to kura clover at both locations based on soil test recommendations as for alfalfa.
Glyphosate-resistant corn was no-till planted on 9 May 2001, 30 April 2002 and 13 May 2003 at both locations. Corn was sown in 76-cm rows at 79,000 plants/ha using a 4-row Kinze PT planter at Arlington and at 78,800 plants/ha using a 4-row White 6104 air planter at Lancaster. A starter fertilizer (6-24-24) was applied at 68 kg/ha product, totaling 9.9, 7.7 and 14.4 kg/ha of N, P and K, respectively.
The experiment was arranged in a randomized complete block design with four replications. Plot size was 3.0 by 9.1 m at both locations. Each plot had four corn rows, where one of each of the center rows was used for grain or corn whole-plant yield and the outside two were border rows. Outside of the experimental area, four corn rows were planted as border. Treatments consisted of corn planted into a kura clover living mulch that was band-killed on the corn row, suppressed in the interrow and sidedressed at the V4 to V5 stage with either 0, 28, 56 or 84 kg N/ha as ammonium nitrate (treatments 0N, 28N, 56N and 84N, respectively), and corn sown into killed kura clover sidedressed with 84 kg N/ha (control treatment). Kura clover in the control treatment was killed with a broadcast application of glyphosate, flumetsulam and clopyralid. For the band-killed treatments, kura clover was suppressed with a broadcast application of glyphosate plus dicamba. Right after planting a 20-cm band was killed with flumetsulan and clopyralid herbicide. A second application of glyphosate was made to all plots to control annual weeds and recovering kura clover at corn V3 to V5 stage, 30 to 40 days after planting.
Stand counts were made at whole-plant or grain harvest. Corn whole-plant dry matter yield was determined at the 50% kernel milk line stage. From one of the two internal rows of the four-row plots, 7.6 m was harvested from the interior of the plot by hand. Plants were cut leaving a 20-cm stubble and chopped to a 2- to 5-cm particle size using a commercial corn silage chopper. A sub-sample was dried at 60 C to calculate dry matter content to adjust corn whole plant yields to a dry matter basis. Subsamples of those were analyzed for total N concentration. Nitrogen concentration found in individual treatments was multiplied by the DM yield to calculate N uptake. Grain yield was determined by harvesting 7.6 m of the other internal row after physiological maturity. Ears were hand-collected and passed through a stationary sheller. Corn grain yields were adjusted to moisture concentration of 155 g/kg.
Replacement of Chemical Band Killing by Zone Tillage of Kura Clover:
Zone tillage of kura clover in the corn row provided warmer soil temperatures that resulted in more advanced early developmental stages of corn seedlings, when compared to band-killed and broadcast suppressed kura clover. However, when the living mulch was band-killed with herbicides, corn plants reached reproductive stage at the same date as those grown in zone-tilled plots. But when the mulch was broadcast suppressed only, corn plants reached reproductive stage one week later, often resulting in the lowest yields of whole-plant and grain.
Whole plant and grain yield differences among treatments varied depending on the year and location. In general, yields were highest for zone-tilled and killed (control) treatments, intermediate for band killed and lowest for broadcast suppressed treatments. When using herbicidal control, the living mulch must be band-killed in order to obtain corn yields comparable to those obtained under conventional monocrop systems.
Since the objective of intercropping corn into perennial living mulch is to reduce soil erosion by keeping the ground covered, corn yields should be maximized without permanent damage to the living mulch. In our study, kura clover living mulch recovered its productivity the year after zone tillage or chemical suppression and intercropping with corn. We conclude that zone tillage can replace band killing of kura clover in the corn row without compromising corn yields. Future research could investigate the potential of zone tillage as an alternative to conventional tillage in organic corn production. Non-chemical control, such as mowing or grazing with small ruminants, could be tested as a replacement for herbicidal control of kura clover in the interrow. Zone-tilling the corn row the fall before corn production could result in early drying and warming of the seedbed, allowing for timely planting.
Kura Clover Mulch as a Nitrogen Source:
Our previous research suggested that kura clover provides all or nearly all of the N required by a corn crop, but this research was not specifically designed to test N response. We observed that herbicide suppression of the kura clover resulted in significant amounts of clover leaves wilting to the soil and clover regrowth was shaded by the taller corn and senesced. Furthermore, its likely that herbicide suppression results in some root and rhizome death and nodule sloughing. Our earlier work focused on competition for light and water between clover and corn so 50 to 60 kg N/ha was routinely applied to insure that N was not limiting.
In the current experiment, we studied the response of corn, growing in kura clover living mulch, to four N rates ranging from 0 to 84 kg/ha. Within the range of N fertilization rates used in this experiment, the lack of yield response to N fertilizer among the band-killed treatments (except for grain yield at Lancaster in 2001) suggests that kura clover may have satisfied all the N demand of the crop. A linear effect of N fertilizer level on N uptake at Lancaster in 2003 was not reflected in yield responses, suggesting that factors other than N availability may have limited corn yield among the band-killed treatments. The results of this research demonstrate that N fertilizer application to corn grown in kura clover living mulch does not increase grain or silage yield, eliminating the need for N fertilizer for corn production.
Affeldt, R.P., K.A. Albrecht, C.M. Boerboom, and E.J. Bures. 2004. Integrating herbicide-resistant corn technology in a kura clover living mulch system. Agron. J. 96:247-251.
Bryant, W.G. 1974. Caucasian clover (Trifolium ambiguum Bieb.) A review. J. Aust. Inst. Agric. Sci. 40:11-19.
Conservation Technology Information Center. 1995. National survey of conservation tillage practices. CTIC, West Lafayette, IN.
Cox, W.J. and R.W. Zobel. 1990. Tillage effects on some soil physical and corn physiological characteristics. Agron. J. 82:806-812.
Enache, A.J. and R.D. Ilnicki. 1990. Weed control by subterranean clover used as living mulch. Weed Technol. 4:534-538.
Gallagher, A.V., N.C. Wollenhaupt, and A.H. Bosworth. 1996. Vegetation management and intertill erosion in no-till corn following alfalfa. Soil Sci. Soc. Am. J. 60:1217-1222.
Kim, B.W. 1996. Kura clover development and performance of krua clover-grass mixtures. Ph.D. diss. Univ. of Wisconsin, Madison.
Litsinger, J.A., and K. Moody. 1976. Integrated pest management in multiple cropping systems. P. 239-316. In R.I. Papendick (ed.) Multiple cropping. ASA Spec. Publ. 27. ASA, CSSA, and SSSA, Madison, WI.
Peterson, P.R., C.C. Sheaffer, R.M. Jordan, and C.J. Christians. 1994. Responses of kura clover to sheep grazing and clipping. I. Yield and forage quality. Agron. J. 86:655-660.
Scott, T.W., J. Mt. Pleasant, R.F. Burt, and D.J. Otis. 1987. Contributions of ground cover, dry matter, and nitrogen from intercrops and cover crops in a corn polyculture system. Agron. J. 79:792-798.
Sheaffer, C.C. and G.C. Marten. 1991. Kura clover forage yield, forage quality, and stand dynamics. Can. J. Plant Sci. 71:1169-1172.
Sheaffer, C.C., G.C. Marten, R.M. Jordan, and E.A. Ristau. 1992. Forage potential of kura clover and birdsfoot trefoil when grazed by sheep. Agron. J. 84:176-180.
Seely, R. 2002. Board OKs landmark regulations for runoff. Wisconsin State Journal. 23 January.
Wall, G.L., W.A. Pringle, and R.W. Sheard. 1991. Intecropping red clover with silage corn for soil erosion control. Can. J. Soil Sci. 71:137-145.
Wollenhaupt, N.C., A.W. Bosworth, J.D. Doll, and DlJ. Undersander. 1995. Tillage effects on intertill erosion in alfalfa following corn. Soil Sci. Soc. Am. J. 59:538-543.
Zemenchik, R.A., N.C. Wollenhaupt, K.A. Albrecht, and A.H. Bosworth. 1996. Runoff, erosion, and forage production from established alfalfa and smooth bromegrass. Agron. J. 88:461-466.
Zemenchik, R.A., K.A. Albrecht, and N.C. Wollenhaupt. 1997. Erosion and forage production from alfalfa and smooth bromegrass in rotation with corn. p. 251-255. In Proc. Am. Forage Grassl. Counc., Ft. Worth, TX. 13-15 Apr. 1997. AFGC, Georgetown, TX.
Zemenchik, R.A. , K.A. Albrecht, C.M. Boerboom, and J.G. Lauer. 2000. Corn production with kura clover as a living mulch. Agron. J. 92:698-705.
Educational & Outreach Activities
Milofsky, T.S. and K.A. Albrecht. 2004. Mechanical control of legume living mulch for corn production. In 2004 Agronomy abstracts [CD-ROM]. ASA, Madison, WI.
Sabalzagaray, A., K.A. Albrecht, C.M. Boerboom, and E.J. Bures. 2002. Zone tillage in a corn/kura living mulch system. In 2002 Agronomy abstracts [CD-ROM]. ASA, Madison, WI.
Milofsky, T.S. 2003. Use of legumes to benefit grass-based production systems in Wisconsin and Ecuador. M.S. thesis. Univ. of Wisconsin, Madison.
Sabalzagaray, A. 2004. Zone tillage and nitrogen fertilizer response in a corn-kura clover living mulch system. M.S. thesis. Univ. of Wisconsin, Madison.
Kura clover a tool in erosion battle? Midwest Dairy Business. December, 2002.
Clever clover: Can this import from the Caucasus help clean up the Gulf of Mexico? Science Report 2002-2003, College of Agricultural and Life Sciences, Univ. of Wisconsin, Madison.
Intercropping corn and kura clover. July 26, 2002. Blue Royal Farms, Reedsville, WI.
Corn production in kura clover living mulch. July 9, 2003. University of Wisconsin Arlington Agricultural Research Station, Arlington, WI.
Corn production in kura clover living mulch. August, 2003. University of Wisconsin Lancaster Agricultural Research Station, Lancaster, WI.
Using kura clover living mulch systems for grain crop producdtion. Mason City, IA, January 26, 2005.
Through field days and the popular press we have had the short-term outcome of making farmers aware of a cropping system that allows maintaining permanent groundcover and reduction or elimination of the need for N fertilizer for corn grain or silage production. We have had inquires from Wisconsin, Iowa, and Minnesota. One of the highlights of the project was being approached by a dairy grazier who produces some corn silage to supplement his pastures. He asked if we would work with him to get the living mulch system on his farm because he could no longer stand to watch the soil erode from corn silage fields on his farm in hilly southwest Wisconsin. Another highlight was when a county extension agent took the lead in setting up a living mulch demonstration on a dairy farm in eastern Wisconsin. We interacted with the agent on a weekly basis during the early stages of the project and participated in a field day at the farm.
Expected long-term outcomes are reduced input costs (N, tillage, legume establishment), reduced soil and nutrient loss from fields, improved surface-water quality, and increased farm profitability. We will need to conduct additional research to be sure that all risks associated with grain production in living mulch are understood. We will need to do additional research to clearly document environmental and economic benefits associated with living mulches. And we need to work with agencies such as Extension, NRCS and Department of Natural Resources to get this system into mainstream agriculture.
There have been many inquiries about the corn production in kura clover living mulch and we know of two farmers who have used the system and a few farmers who have established kura clover with the intention of sowing corn into it. There has been interest from the organic community because of the N benefits, but the risk of competition in a dry year is too great for us to recommend kura living mulch without an herbicide control option. The reduction in N fertilizer requirements has caught the attention of farmers as N prices continue to climb. The opportunity to keep permanent groundcover on hillsides has spurred interest from dairy farmers who desire to grow corn silage. Because of the complexity of growing two crops together, training sessions for farmers who want to work with this system are encouraged. One such session will be held in Mason City, Iowa, January 26, 2005.