A New Source of Winter-Active and Persistent Forages for Semiarid Environments of the Southern Great Plains
For at least three decades, agronomists and plant breeders have been attempting to introduce improved cool-season perennial grasses to semiarid environments of the southern Great Plains to complement forage availability from dual-use wheat (Triticum aestivum L.) pastures during the fall-winter-spring (October-March) grazing season and from warm-season grass pastures and native rangelands in the spring (March-May) grazing season. The introduction of traditionally recommended, improved cool-season perennial grasses has not been successful because of: 1) very limited forage production during winter grazing season, and 2) poor persistence due to inadaptability to severe water deficits accompanied by extreme heat in summer.
Global climate change has an effect on the climate of the southern Great Plains. Within the last 20 years, mean annual temperature has been increasing, while annual precipitation has been decreasing (www.noaa.com). Although one may argue this may be a part of natural climate cycle, the fact is that such changes will have an impact on decision making in regard to agricultural crops and practices in affected regions of the world.
Breeders in Argentina, Australia, Italy, and New Zealand have recently developed drought resistant cultivars of cool-season perennial grasses, i.e., tall fescue (Lolium arundinaceum), orchardgrass (Dactylis glomerata) and perennial ryegrass (Lolium perenne) based on germplasm originated from the Mediterranean Basin of Europe and Africa. These grasses produce most of forage during autumn to early spring and are summer-dormant, i.e., they cease growth in response to long days and high temperatures even at adequate soil water supply. In contrast, traditionally recommended cultivars of perennial cool-season grasses for the southern Great Plains are summer-active, i.e., they continue with grow during summer if soil water is available. Consecutive periods of drought exhaust the plants resulting in high tiller mortality by autumn.
In environments resembling Mediterranean climate with prolonged and severe summer drought, summer-dormant cool-season perennial grasses have been proven more persistent than summer-active types. Their strategy of drought resistance, which is actually similar to drought escape, is superior to that of summer-active types that developed mechanisms of drought tolerance.
Summer-dormant cool-season perennial grasses are not productive during summer months, therefore, they are not suitable for improved, intensive grasslands in the temperate zones of the United States. This may explain the slower progress of developing summer-dormant cultivars in the USA when compared with other countries. Our 8-year research data indicate that summer-dormant cultivars are perfectly adapted to the transitional semi-arid steppe and warm semi-arid steppe zones of the southern Great Plains, most likely because the climate here (relatively mild winters and severe summer droughts) is similar to that of their origin.
- Determine mechanisms of summer dormancy in cool-season perennial grasses
- Introduce summer-dormant cool-season perennial grasses to grazing systems of the southern Great Plains
- Breed productive and persistent cultivars of summer-dormant cool-season grasses, including tall fescue, orchardgrass, and perennial ryegrass.
|2000 – 2008||Evaluation of forage productivity and persistence of Flecha MaxQ summer-dormant tall fescue|
|2002 – 2004||Evaluation of productivity and persistence of tall fescue, orchardgrass, perennial ryegrass, and hardinggrass as a function of summer dormancy|
|2004 – 2007||Mechanisms of summer dormancy in cool-season perennial grasses – A cooperative project with Dr. Jaime Kigel , The Hebrew University of Jerusalem, Israel.|
|2005 – present||Breeding of summer-dormant cool-season grasses for southern Great Plains|
|2008||Development of a method to differentiate summer-dormant from summer-active tall fescue and orchardgrass accessions at germination stage|
|2009||Hosting the Field Day at Vernon for participants of the 1st International Workshop on Summer Dormancy in Grasses|
Summary of Results
Malinowski, D.P., Kigel, J., and W.E. Pinchak. 2009. Water deficit, heat tolerance, and persistence of summer-dormant grasses in the U.S. Southern Plains. Crop Sci. 49:2363-2370.
Malinowski, D.P., Belesky, D.P., Kramp, B.A., Ruckle, J., Kigel, J., and W.E. Pinchak. 2008. A method to differentiate summer-dormant from summer-active tall fescue and orchardgrass accessions at germination stage. Australian J. Agric. Res. 59:1092–1102.
Texas-Israel Exchange Fund
Grasslands Innovation Ltd. (New Zealand)
Texas AgriLife Research