Evaluating Rye Germplasm for Use as a Cover Crop in the Upper Midwest

View the project final report

• 2008 annual report

Commodities

• Agronomic: rye, wheat

Practices

• Animal Production: feed/forage, winter forage
• Crop Production: conservation tillage
• Education and Training: farmer to farmer, workshop, youth education
• Farm Business Management: risk management
• Natural Resources/Environment: carbon sequestration
• Pest Management: cultural control
• Production Systems: agroecosystems, organic agriculture
• Soil Management: soil analysis
• Sustainable Communities: sustainability measures

To date breeding and selection efforts with rye (Secale cereale L.) have not focused on its use as a cover crop, but rather the breeding in rye has focused on making it a more useful grain crop. Finding appropriate rye germplasm containing useful cover crop traits is needed to be able to maximize the effectiveness of the rye cover. Data regarding the diversity of rye germplasm is crucial in helping to modify the way this cover crop is used. There are several useful traits that could be improved to make rye a more effective cover crop, including early seedling vigor, fast biomass accumulation and canopy closure, and earliness to anthesis. These traits can be adapted to specific growing regions because of the wide range of germplasm and the large area in which a rye cover crop can be grown. Of these traits earliness to anthesis is the most important as it constitutes the most limiting factor when dealing with the management of a rye cover. Different varieties and land races can take between 32 to 61 days to go from anthesis to mature grain. There are little current data on the amount of time, heat units, and solar radiation it takes for different rye varieties to reach anthesis from planting. However, there is variability in heading date ranging from 35 to 50 days after initiation of re-growth in the spring. Due to the lack of variability for both maturity and early-season biomass production in the currently available adapted winter rye cultivars in Minnesota, germplasm acquisition and screening was conducted and crosses to move earliness into the MN rye germplasm were made.

Introduction:

Flowering time has been manipulated by plant breeders for a century and by farmers for several millennia. Flowering time is an important agronomic trait for several reasons including: decreasing the time between generations, increasing yield, avoidance of certain stresses, and the ability to manage the crop. This trait has extended the area in which domesticated crop plants can be grown by shortening the flowering time as well as extending the growing season to increase yield (Cockram et al., 2007). Flowering time is also important to the general survival of the plant, mechanisms of flowering evolved to protect the plant from temperature and environmental fluctuations during the year, and provide the plant with the most favorable conditions to grow during the year (Worland, 1996). Flowering time is also a highly heritable trait making it a trait easily manipulated by plant breeders (Rattunde et al., 1991). There has been variability reported in rye germplasm regarding flowering time, with as much as a 15 day difference in time of anthesis (Gregory and Purvis, 1938, Purvis, 1934). Flowering time is controlled differently in different plants; many mechanisms including photoperiod, gibberellins, temperature, and light quality can have a profound impact (Baurle and Dean, 2006). Therefore, when breeding for flowering time it is important to look at the genetic, physiologic, and environmental differences that lead to different maturities.


Envronmental influences can also have a large impact on anthesis date. Some vernalization genes have been linked to stress tolerance genes (Snape et al, 2001, Taeb et al., 1992) therefore stressed situations can cause rye to initiate flowering earlier than expected (Taeb et al., 1992). In field studies the response to vernalization and photoperiod has been shown to be very similar between wheat, barley, rye and oats (Aiken, 1966). Under conditions that are unstressed provides evidence that differences are genetic rather than environmental. When the plant is physiologically developed enough photoperiod will not limit floral initiation (Major, 1983). Temperature and maturity level can cause the importance of the photoperiod on flower initiation to be lessened (Aiken 1966).

Throughout Minnesota the spring planting date for corn (Zea mays L.) and small grains is earlier than the planting date for soybean (Glycine max L.). With the later planting date for soybean, a fall planted rye cover crop would have a longer spring growing period before the rye crop would need to be managed. This would allow for maximal cover crop characteristics increasing their benefit. A delay in the rye management is critical if the cover crop is to have significant biomass production and weed management benefits. The addition of a well-adapted fall planted cover crop to the corn soybean rotation would has the potential of reducing erosion as well as reducing nutrient loss. Many studies have shown that early spring rye management is what protects yields in the following crop later in the year (De Bruin et al., 2005, Westgate et al., 2005, Reddy, Krishna, 2003); in conventional farming systems, where herbicides can be used, timing spring rye management is relatively easy.

However, in organic systems rye should be managed at anthesis to ensure that the rye cover will not regrow. If managed before anthesis there will be significant re-growth that will impact soybean yield through competition for nutrients and water (De Bruin et al., 2005). Typical rye varieties grown in Minnesota reach anthesis in early June. A rye variety that reaches anthesis in mid- to late-May would complement this system. Therefore an important cover crop trait is earliness to anthesis. Another important trait is early biomass accumulation, which could add ground cover and quicken canopy closure, thereby reducing weed seed germination and vigor.

Short-term project objectives:
-Greater understanding of planting date on effectiveness of a rye cover crop at different latitudes in Minnesota;
-Disseminate results to Minnesota farmers regarding rye as cover crop.

Intermediate-term project goals:
-Comparison of rye to related fall-planted species;
-Develop a greater understanding of variability in rye germplasm through the growing out of rye accessions to evaluate for quick fall biomass, larger amounts of early-season spring biomass, and an earliness to anthesis while still maintaining appropriate winter hardiness for northern tier states in the US.