Pastures and Drought: Response and Impact
Few producers will complain about dry weather during calving. Not having to worry about wet calves or fight the mud is definitely a blessing. However, with a dry fall and open winter for much of Nebraska, the threat of drought going into the 2022 growing season may be cause to dust off and reevaluate our operation’s drought plan.
While drought hits all portions of an operation hard, we can sometimes be strictly focused on the herd and the immediate concerns about feeding or finding a place for cattle that have run out of grass. Often overlooked are the impacts on our pastures, which typically experience overgrazing during dry weather. Understanding the short and long term impacts drought can have on pasture is important as we update drought contingencies for our 2022 grazing plan.
If dry conditions persist, timing of moisture will be increasingly important. With already dry soil moisture conditions, plants initiating growth this spring will be limited to moisture from precipitation to meet their water demands. Without soil moisture to pull from, utilizing trigger dates to compare current precipitation to our normal trends will be increasingly important.
These critical dates will be different depending on your primary species and location in the state. In general though, cool season grasses that initiate growth earlier in the year will be more impacted by a lack of early spring moisture, while pastures dominated with warm season species may be able to hold out a bit longer (mid-spring) for moisture to return as their primary growth will occur later on in early summer. Keep in mind that the reverse of this will also be true. Early precipitation may fuel some cool season plant growth, but continued precipitation will be needed to provide warm season species with enough water to meet their full growth potential.
In either case, if moisture remains limited, we can expect productivity from our pastures to suffer. Drought plans should be implemented to reduce stocking rates and limit the potential for overgrazing. Overgrazing during drought can be particularly hard on plants as we are stacking one stressor (drought) on top of another (grazing), putting plants in a difficult position to recover from during a normal year, let alone without adequate water.
Both grazing and drought limit a plant’s ability to photosynthesize, or capture the sun light and turn it into energy. Because plants produce their own energy and can’t make a trip to the grocery store to stock up when food runs low, they have to correct any imbalance on their own. Often this is done by decreasing their energy needs. By shedding off portions of the roots and/or aboveground growth the plant itself becomes smaller and demand decreases. Usually this is enough to temporarily provide enough of a shift for regrowth to occur and energy production to pick back up; a temporary drop in reserves, but nothing more.
During drought however, no water means no regrowth. Faced with no way to right the imbalance of energy supply and demand, the entire plant goes dormant. While energy use during this period is as low as possible, a dormant plant is slowly chipping away at energy reserves to stay alive. These core reserves are all that the plant has to initiate growth from when conditions improve. As they decrease, the ability of the plant to recover decreases and recovery time increases. This same phenomenon occurs with chronic overgrazing, a slow and steady eating away at a plant’s core reserves.
Most pastures in Nebraska rely on perennial grasses for their primary growth. These plants play the long game, focusing on building back energy reserves and roots before returning above-ground production to pre-stress levels. If plants continue to be stressed by enduring drought or overgrazing, the resulting time to build back vigor can sometimes take years. As a result, even when favorable conditions return after drought, productivity across the pasture continues to be suppressed.
Ideally under these conditions, we would reduce stocking rates. However, it’s awfully tempting to return pasture stocking back to “normal” when rain returns. This often results in yet another round of overgrazing. Under these conditions, it is easy to fall into a vicious cycle where recovery takes longer and longer while overgrazing becomes easier.
Another result of this drop in plant vigor is to open up the canopy and provide space for weedy species to invade. Sometimes this can be ok. After the drought in 2012, producers may have noticed an abundance of annual sunflower and ragweed in pastures the following year, both plants able to take advantage of the available space provided by drought stressed grasses. Their presence, while not the most desirable, did provide limited forage and cover for the ground. Most importantly though, they were a temporary fill in and were able to be pushed back out when the grasses recovered.
More dangerous is when invasive weed species take hold and can’t be so easily pushed out. These plants can come from an already established population on our operation, or nearby land and quickly take over when conditions are right. The shipping and moving of hay from one area to another during drought can increase this risk even more, bringing in new weeds from outside the immediate vicinity to an already weakened plant community.
No one ever knows what conditions the next growing season will hold. The best we can do, as the saying goes, is to hope for the best and plan for the worst. When it comes to drought, impacts on pasture can be immediate and more long-term. Without moisture, plant growth slows or stops, reducing our production and grazing potential for the year.
If the stress of drought is prolonged or compounded by another stressor like overgrazing, impacts can be felt for years. Perennial species take time to build back vigor and strength as their energy reserves recover. This may drop productivity for several grazing seasons as well as increase the likelihood of continued overgrazing and the opportunity for the establishment of invasive weeds.
Understanding the impact of drought on your pasture can provide direction for planning and mitigating impacts. Planning ahead can reduce the long-term impacts and help make difficult decisions easier in the heat of the moment. Take some time now to make sure your drought plan is ready for 2022. Hopefully we won’t have to use it, but if we do, you won’t regret having it prepared.
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