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Spring Management for Productive Pastures
April, 2023
Allie
Williams, Small Farms & Livestock Agent, UF/IFAS Extension HIllsborough
County
Start the spring off strong with pasture management as
your focus. Many of my farm visits have a common topic - pasture decline.
What were once lush green pastures have now turned to dirt. Weeds have
replaced the grass and there’s not enough for the cattle to eat. Let’s talk
about how the pasture likely got to this state and how to be proactive in
preventing this.
There are usually multiple factors that contribute to
pasture decline, but the one that has the most impact is overgrazing.
Overgrazing happens when plants are regrazed before they recover from the
previous grazing event. Why is this a big deal? When the plant is grazed
repeatedly, the leaf area is reduced, and the plant is not able to
photosynthesize to create energy. The plant will then pull stored nutrients
from the roots to produce leaves. Root growth is reduced which impacts the
plant’s ability to take up water and nutrients.
Figure 1 Relationship among stubble remaining after grazing, recovery period, and root growth. Source: OSU Extension Service.
At this point the pasture is weak and if any pests or
disease are introduced, this can accelerate the pasture decline. If the
pasture is continuously overgrazed, plant death can occur. When this
happens, undesirable species and weeds tend to take over. Ideally, pastures
should not be grazed below the recommended stubble heights to aid in
regrowth (see figure 2). Keep in mind, these are minimum stubble heights and
stopping at higher residual heights can lead to a quicker recovery. If
rotationally grazing, a good rule of thumb is to only graze 50% of the
available forage height before rotating.
Figure 2 Target stubble height for persistence of rotationally grazed warm-season grasses in Florida. Adapted from Mislevy (2002).
To avoid overgrazing your pastures, stocking rate
should also be considered. Stocking rate is the number of animals per acre.
This should match the carrying capacity. The carrying capacity is the number
of animals the pasture can support throughout a given period of time. This
can fluctuate based on factors such as forage species, season,
fertilization, nutrient requirements of the herd, supplementation, and
future forage needs. A general rule of thumb for well-managed, fertilized
Florida pastures is to have stocking rates as 1.5 to 4 acres per cow on
bahiagrass; 1-3 acres per cow on bermudagrass, stargrass, and limpograss;
and 5 to 25 acres per cow on native range. Note that these recommendations
for well-managed and fertilized pastures. Unfertilized pastures would be on
the higher end of the range, at about 4 acres/cow on bahiagrass. Stocking
rates can have an impact on pasture persistence, animal performance, and
overall pasture productivity.
Soil fertility is a key factor for forage growth. It is
recommended to soil test pastures every 3 years (hayfields annually). Work
with your Extension agent to develop a fertility plan based on these
results. Optimizing soil fertility can lead to thick forage stands which can
prevent weed emergence or outcompete emerged weeds.
Weed control should be a multifactor approach for best
results. This can include methods such as soil fertility, mowing, and
herbicide use. Mowing is a common control method, however, a cost-analysis
should be done to determine if other forms of weed control would be more
cost-effective. It should be noted that mowing certain weeds can spread
vegetative plant stems which can cause them to root and increase weed
presence. This is often seen with weeds such as prickly pear cactus. Another
approach is the use of herbicides. Proper timing, method, rate, and
herbicide selection are crucial to the effectiveness of control. This
translates to cost-effectiveness. Early control of weeds can significantly
increase the percent controlled. Weeds should be actively growing when the
herbicide is applied. Herbicides can be broadcast over the entire pasture or
spot sprayed for smaller weed patches.
The key to a pasture management program is to start
with a simple plan that makes sense for your operation. What specific
management practices are needed to achieve the anticipated level of
production? Consider the grazing pressure, soil fertility, weed management,
and cattle management when creating this plan. Use this pasture management
plan to help guide your management decisions and achieve your production
goals. If you have questions about pasture management, contact your local
county extension agent.