Grazing and Forage Management During and After Drought
Winter is a good time of year to begin making grazing and forage plans for the upcoming season. Of course, there can be a tremendous amount of uncertainty on what type of growing conditions we will see in the spring and summer. This is especially true if we had droughty conditions the previous summer or little fall and winter precipitation.
Precipitation and Pasture Growth
Total plant production on native rangelands is dynamic and influenced by multiple weather-related factors. The most important factor influencing yearly plant production is the amount of growing season precipitation, which can vary widely in different years. Plant production directly influences appropriate year-to-year stocking rates. In dry years with limited plant production, livestock forage de-mand often exceeds available plant production and livestock producers are faced with decisions of overutilizing pastures, selling cattle, or finding alternative feed resources. In years with above average precipitation, plant production supply may be greater than livestock grazing demand.
As one would expect, the timing and duration of drought conditions are key in the resulting effect on pasture growth. Dry conditions in April and May would impact growth of cool-season grasses and dry conditions from mid-May to mid-July would have a more pronounced effect on warm-season grasses. Spring temperatures may also affect the start of the growing season and use of available soil moisture. During the 2012 drought, many areas in central and eastern part of the state had a moderate amount of precipitation during April; however, drought conditions intensified beginning in May and remained through the rest of the year. Observations in the Sandhills showed cool-season grasses achieving about 40 to 70% of the average growth, while warm-season grasses attained about 30 to 60% of their average growth. Most warm-season grasses had stopped growth by late June and were going into a drought-induced dormancy.
For many livestock producers, carryover or residual grass from the previous growing season can help support stocking rates that were higher than what would have been anticipated just based on grass production during a dry growing season (Fig.1). If the previous year was dry, and the amount of carryover forage is limited, producers should consider this in their cattle number and stocking rate plans.
More information on precipitation amount and seasonal distribution and how it affects forage production can be found in the Extension publication EC3039: Grazing Management with Variable Plant Production in the Nebraska Sandhills.
Grass and Rangeland Response to Drought
The primary response and effects of drought on grasses and pastures include:
- Reduced aboveground growth.
- Reduced root growth.
- Fewer reproductive tillers (seed heads) and plants remain mostly vegetative.
- Severe drought will cause plants to go into dormancy.
- Reduced growth of rhizomes and formation of new buds that will produce next and future year’s tillers.
- Lower carbohydrate (energy) reserve storage.
Although most pasture grasses are quite resilient, it is common to expect that production during the year following a drought will be reduced, even with average precipitation. The reasons for this are most likely associated with the reduced root and rhizome growth, formation of new buds and overall energy reserve status of the plants. The exact amount reduced forage production the year after a drought is difficult to predict because the precipitation patterns and severity of each drought are rarely the same. In addition, the precipitation amounts and timing this coming year are unknown. However, rangeland this is in a higher ecological state or range condition will recover quicker after drought than lower condition range.
Timing of grazing is an important factor in grazing management and a common recommendation is too avoid grazing in the same pasture at the same time each year. Previous research has shown that repeated annual grazing during the rapid growth stage will reduce the overall vigor of grasses. This rapid growth phase is when grass plants are transitioning from a vegetative to elongation and reproductive stages. This rapid growth phase typically occurs in May for cool-season grasses and during June and July for warm-season species. Combining drought and grazing stress will greatly increase the likelihood of reduced forage production in the subsequent year.
Drought Grazing Plans and Management
The uncertainty of how much spring and early summer precipitation will occur suggests the need for plans that include multiple scenarios. These scenarios might include: 1) average or above average precipitation during that period, 2) abnormally dry to moderate drought (60 to 90% of average precipitation, or 3) continued severe drought (< 50 to 60% of average precipitation).
Regardless of which scenario comes true, the primary focus should be about balancing forage supply (growth, production) and demand (animal numbers). Keep in mind that grazing management through consecutive drought years is critical for future pasture health (Figure 2).
For pastures and rangeland, common recommendations for the year after a drought include:
- Delaying initial turn-out to pasture.
- Reduction of stocking rates.
- Capitalize on growth of weedy species that might occur.
- Use rotation grazing and in central/western Nebraska, graze pastures only once from turn-out to killing frost.
- Use alternative forages.
After a long period of feeding hay, delaying turn-out to pasture is one recommendation that many producers find difficult to follow. Other than cases where a short, early grazing period is used to make use of weedy annuals, like downy brome; delaying turn-out will benefit the perennial grasses. The deferment will allow the grasses to develop more leaves and ideally reach a point where some of their depleted energy reserves can begin to be restored.
Where deferred rotation grazing (4 or more pastures) is used, deferment priority should be given to pastures that were grazed when grasses were green and did have some growth occurring before they went into drought dormancy. Overall, the greatest number of cow-days per acre will be obtained when pastures are not grazed until plants have completed most of their growth for the year.
Using Critical Dates to Help Plan
Many ranch drought plans suggest the use of ‘critical’ or ‘trigger’ dates. The concept is based on monitoring precipitation amount received by these defined dates and initiating certain management actions when those precipitation amounts are less than anticipated. Management actions vary by individual ranch operation and would include things such as various levels of culling on livestock classes, feeding hay, finding additional pasture, drylot feeding of animals, or using seeded forages. Precipitation amounts and critical dates vary for different pasture and rangeland types and location. Critical date plans and actions are flexible over time and it does often take several years of records and observations to refine the plan for an individual operation. In general for Nebraska, important periods and dates are as follow:
- Previous growing season: Consider the previous year’s pasture production and level of utilization. Drought in the previous year will likely be reflected in lower production during the current year because of reduced vigor in the grass plants.
- April 1: end of dormant season (October through March). Precipitation to this point supports early cool-season grass growth.
- May 1: Precipitation to this point is the basis for cool-season grass growth. The amount of moisture in the soil profile at this point will also affect the rapid growth of cool-season grasses that occurs during May and is the basis for early warm-season grass growth.
- June 15: Precipitation to this point is the basis for warm-season grass growth. Moisture in the soil profile will also affect the rapid growth of warm-season grasses that occurs during late June and July.
Seeded Annual Forages
There are a number of different cool- and warm-season annual forages that can be planted to produce forage during times of deficit. Although most all of these can either be hayed or grazed, the greatest tonnage of forage will be produced is when they are hayed. This is because grazing is less efficient in terms of actual consumption versus the production potential of the forage. With grazing, there are the losses associated with trampling and reduced production because growth is interrupted when plants are grazed at various growth stages.
Growing any annual forage with irrigation would of course, greatly increase yield during drought. This is particularly true for those planted late summer with the intention of fall forage.
Cool- and warm-season annuals with potential forage use are listed below.
Information on seeding rates and methods, fertility requirements, or other cultural practices for any of these forages can be obtained from your local Extension office or seed supplier.
Italian or annual ryegrass
Several other legumes
Planting date: mid-March to mid-April
Grazing: mid-May through June
Hay: mid to late June
Planting date: late-May through July
Grazing: Varies with planting date and species
Hay: Varies with planting date and speciese
When planted later, several of these forages are suitable for windrow or stockpiled grazing in fall or winter. Planting should occur by about August 10 for significant fall forage.
Field peas and other legumes
Turnips and other brassicas
Planting date: mid July through August
Grazing: early October through November
Hay: Cereal grains suitable for haying in late October
Cereal grains are suitable for windrow grazing in late-fall or winter
Planting should occur by September 1 for significant fall forage.
Planting date: September through October
Grazing: Some fall grazing when planted early; mostly the following spring
Hay: May for rye and June for triticale and wheat
Windrow grazing: Windrowing in May or June (before advanced stages of maturity) and grazing windrows will result in greater harvest efficiency.
|* Any of these winter annuals planted in late July or August will produce significantly more fall forage. However, adequate residue on the soil (to maintain lower soil temperatures) and irrigation are desirable.
* Winter annuals can be planted as late as November or December; however, spring forage yield will be reduced with later planting dates.