- Agronomic: corn, grass (misc. perennial), hay
- Animal Production: feed/forage
- Crop Production: catch crops, continuous cropping, cover crops, double cropping, intercropping, multiple cropping, no-till, nutrient cycling
- Pest Management: mulches - living
- Production Systems: agroecosystems
- Soil Management: nutrient mineralization, organic matter, soil analysis, soil quality/health
Corn (Zea mays L.) is a productive and popular forage crop that can exacerbate soil loss, surface water runoff, and nonpoint source nutrient pollution from agricultural fields.
During 2010 and 2011 we compared the effects of kura clover (Trifolium ambiguum M. Bieb.) living mulch and winter rye (Secale cereale L.) in corn silage production on runoff, soil physical properties and organic matter, and forage yields. At the University of Wisconsin Lancaster Agricultural Research Station 8 km west of Lancaster, WI we simulated short, heavy rainstorms on loess soils with 8 to 15% slopes.
Kura clover living mulch reduced water runoff by 50%, soil loss by 77%, and P and N losses by 80% relative to monocrop corn. Rye reduced water runoff by 67%, soil loss by 81%, P loss by 94%, and N loss by 83% when planted after corn silage harvest. When rye was planted following corn silage in kura clover living mulch, water runoff was reduced by 68%, soil loss by 77%, P loss by 94%, and N loss by 84% relative to monocrop corn. Dissolved reactive P, NH4-N, and NO3-N losses in runoff were often, but not always, higher in monocrop corn.
Most of the differences between cropping treatments were due to differences in runoff amount rather than concentrations. Higher ground cover, soil aggregate stability, and soil organic matter, as well as soil surface disturbance from rye planting, were associated with improved infiltration and reduced soil and nutrient losses in the cover cropped treatments.
When grown in kura clover living mulch, both corn and rye had lower yields but this was offset by lower fertilizer requirements and improved farmland and environmental function and quality.
Corn silage is one of the most common forage crops used in Wisconsin and throughout the United States (NASS, 2011). The removal of almost all corn residue, as occurs in silage production, can lead to much larger amounts of surface water runoff, soil erosion, and nutrient pollution than is seen when stover is left in the field (Blanco-Canqui and Lal, 2009; Grande et al., 2005a; Grande et al., 2005b; Lal, 2009; Weinhold and Gilley, 2010). While silage is a relatively minor use of corn (NASS, 2011), the possibility of corn stover based bioenergy products may leave many more corn fields bare and vulnerable during the fall and spring. Additionally, the removal of stover leads to lower organic matter and poor soil structure, reducing agricultural productivity in the long run (Blanco-Canqui and Lal, 2009, Fageria et al., 2005).
Soil, nutrient, and water losses exacerbated by bare soil create need for additional fertilizer and irrigation inputs. Agricultural runoff also contributes to widespread nonpoint source pollution and surface water eutrophication seen throughout the United States (Carpenter et al., 1998). The products made from whole-plant corn, whether silage, biofuel, or bio-based materials, are obviously quite attractive to many farmers and useful to society at large. However, they must be paired with agronomic practices designed to mitigate the long-term possibility of farmland and environmental degradation.
Cover crops reduce surface runoff and soil loss from agricultural fields by improving soil structural stability and infiltration, holding soil particles with their roots, and blocking raindrop impacts with their leaves (Berg et al., 1988; Dabney, 1998; Sharpley and Smith, 1991; Zuazo and Pleguezuelo, 2008). Despite these, and other, agronomic benefits, cover crops are little used in the field crop production occupying the great majority of American farmland (Clark, 2007; Hartwig and Ammon, 2002; Lubowski et al., 2006; Singer 2008).
Midwestern, field-crop farmers surveyed by Singer et al. (2007) identified the cost of cover cropping as a limiting factor in adoption. Government action could greatly increase the use of cover crops but the regulation of agricultural runoff has been controversial, unevenly implemented, and largely ineffective in alleviating the problem of nonpoint source pollution nationally (Graham et al., 2011; Scanlan, 2011). The development of economically viable, perennial living mulches to supplement more popular, annual covers could increase the use of cover crops, even in the absence of more effective cost-sharing programs (Clark, 2007; Singer 2008). Though perennial living mulches must be carefully managed to prevent resource competition with cash crops, they do not need regular re-establishment. The maintenance of year-round ground cover can provide agronomic and environmental benefits during periods when annual covers would be absent.
Particularly promising for corn production in the northern corn belt is the use of kura clover living mulch. In this system, corn yields were only slightly reduced using conventional hybrids under favorable weather conditions and not reduced when using herbicide resistant corn hybrids and suppressing the clover during the growing season (Affeldt et al., 2004; Zemenchik et al., 2000). Offsetting the time and opportunity costs of kura clover living mulch management, it substantially decreases N fertilizer needs for corn production and reduces NO3-N leaching to groundwater (Berkevich, 2008; Ochsner et al., 2010). Furthermore, kura clover living mulch was associated with higher natural enemy populations leading to increased predation of European corn borer (Ostrinia nubilalis Hübner), and was among the best species for weed suppression (Prasifka et al., 2006; Singer et al., 2009). Kura clover has also been successfully managed for high quality forage production as a monocrop in conjunction with winter and spring small grains and in perennial mixtures with forage grasses (Contreras-Govea and Albrecht, 2005; Contreras-Govea et al., 2006; Kazula, in review; Kim and Albrecht, 2011). It is persistent and productive in northern climates and is resistant to many diseases that affect other clovers (Trifolium spp.), possibly providing permanent ground cover (Cuomo et al., 2003; Sheaffer and Marten, 1991; Taylor, 2008).
Despite its potential, kura clover living mulch has not been adopted by farmers, possibly due to the complexity of its management and the agronomic restrictions on cash crop options, as well as the lack of widespread knowledge of the system. Kura clover is slow to establish but corn or other companion crops [e.g. oats (Avena sativa L.) or birdsfoot trefoil (Lotus corniculatus L.)] may be grown during the establishment year (Jusoh, 2010; Seguin et al., 1999; Sheaffer and Marten, 1991). Unfortunately, kura clover stands can be negatively affected by companion crops. Once established, the use of kura clover as a living mulch presents additional management issues. Competition for water and mineral nutrients can reduce corn yields and neither herbicide nor mechanical suppression of kura clover living mulch has proved to unfailingly eliminate yield losses (Bard, 2009; Sawyer et al., 2010; Zemenchik et al., 2000). Greater suppression of the living mulch assures corn yields during the same year but could damage the long term persistence of the kura clover. Furthermore, kura clover living mulch has been problematic in soybean production [Glycine max (L.) Merr.], for either seed or forage (Pedersen et al., 2009). As a result, kura clover living mulch has limited potential in the common corn-soybean rotation or in conjunction with other leguminous seed crops.
Unlike kura clover living mulch, winter rye is in use on farms as a cover crop following corn (Clark, 2007; Stute et al., 2007). Both kura clover and winter rye have been studied in a wide variety of contexts and directly compared in terms of forage yield and quality (Kazula, in review) as well as in their impact on soil properties (Jokela et al., 2009) as cover crops in corn silage systems. Additionally, winter rye has reduced water runoff and erosion in corn silage and soybean production (Kaspar et al., 2001; Laloy and Bielders, 2010) and preliminary research by Eleki (2003) found a reduction in sediment and phosphorus losses with the implementation of a kura clover living mulch relative to conventionally tilled corn silage. To build on this research, our goal was to directly compare kura clover living mulch and winter rye to monocrop corn effects on erosion and nutrient runoff.
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Our short-term objectives, to document the environmental effects of kura clover living mulch and winter rye in no-till corn silage on surface runoff was was completed during 2011. The results were published as a Master’s thesis, presented as a seminar in Madison at the University of Wisconsin campus for an audience of professors, research staff, and graduate students, and shared with research station staff in southwestern Wisconsin.
The research is being submitted as a poster presentation at the 2012 Agronomy Society of America conference and will be submitted for peer-review publication as well.
Research in forage production systems incorporation kura clover living mulch is ongoing at the University of Wisconsin and accessible cropping systems will be promoted through direct communication with extension agents and as a brochure detailing both the agronomic management and environmental benefits of kura clover living mulch.