The majority of native and tame perennial grasses in western Canada are cool season grasses. The annual life cycle of cool season grasses begins in fall rather than spring. Shoots that grew during spring and summer stop growing in fall. The plant then switches over to producing leafy tillers that overwinter and resume growing in spring. This is the “green up” you see happening at the base of the plants in fall, and it enables perennial forages to get a fast jump start in spring.
The dry summer and currently dry fall of 2017 has been a challenging year for many livestock producers in southern Saskatchewan. With low forage production, many producers want to graze any and all forage resources available. Will fall grazing of the leafy shoots compromise forage production in 2018?
To investigate the practice of late and dormant season grazing, a trial was carried out at Craik and Frobisher during 1998-2000. Treatments compared September, November and April grazing with No Grazing on alfalfa/grass hayfields. The grazing treatments removed 80-90% of the forage material and hay yields were collected in early to mid-July. In summary, only the April grazing showed a negative impact on hay yield at the Craik site.
During this trial, moisture conditions were relatively good. Second growth after hay harvest was quite good, as the grazing treatments averaged 600-700 lbs/acre (Air Dry) of forage removal. The grazing treatments had sufficient time to rest and recover during May and June as they were not cut until early to mid-July.
These favorable results may not be the case for fall grazing in 2017.
Many drought stressed hayfields and pastures had minimal regrowth after mid-summer haying or grazing. Therefore it is unlikely the root systems are fully recharged heading into winter. Weakened plants may not survive the winter, and if they do a weakened stand will be less able to resist weed invasion in 2018. Grazing fall tillers will put plants at a further disadvantage next spring, as new growth will have to be fueled from an already taxed root system. Grazing in 2018 would need to be delayed well into June to allow plants to regain vigor.
Grazing in fall reduces litter cover which at some point will result in increased bare soil. When moisture conditions are good, bare soil is less of a concern. During dry conditions, litter plays a key role in shading the soil surface to reduce water loss from evaporation. Litter also reduces or eliminates the direct hit of raindrops on the soil surface which pulverize soil particles. Intact soil particles enable more rapid water infiltration into the soil profile when it eventually does rain. Standing litter helps to hold a snow cover which insulates plants and increases snowmelt water in spring.
Some forage species such as crested wheatgrass and Russian wild rye are more resistant to dry conditions compared to the brome grasses and alfalfa.
Grazing forage stands in fall 2017 may well cause delayed growth and reduced production in 2018. Monitor those stands in spring of 2018 and delay grazing if they appear stressed and slow to grow.
Lorne Klein, Forage Specialist
Saskatchewan Ministry of Agriculture
