October 14, 2015 Comments are off Montana Stockgrowers Association
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Range Ruminations: Are Range Grasses Vulnerable to Grazing during Early Fall?

Jeff Mosley MSU ExtensionIn ranching it’s often necessary to spend money to make money. Funds from savings accounts or operating loans are spent to purchase inputs such as vaccine, seed, fertilizer, or feed. These inputs help fuel the engine that hopefully returns enough income to replenish the savings account or repay the bank, and also cover enough living expenses that you can afford to play the game again next year.

Range grasses often play a similar game during early autumn. Most years range grasses go dormant in late summer when days get hot and soils get dry. If more mild temperatures return in September and October accompanied by rain or early wet snow, grasses respond by breaking summer dormancy. To initiate this new growth grasses must draw upon stored energy reserves in their roots and stem bases. In other words, grasses must spend some of their savings to kick-start the new growth in early fall.

After the new leaves reach one-third to one-half their mature size they produce enough energy via photosynthesis to fuel their own growth and begin replenishing the plant’s energy reserves (i.e., begin repaying the bank). With enough time and leaf area, grasses are able to repay the bank, cover their living expenses, and can afford to play the game again next year. However, if grazing during early fall removes too much of this new leaf area before plants replenish their reserves, range grasses enter winter in a weakened condition, may not survive winter, won’t produce as much forage next spring, and won’t compete as well against weeds next year.

Similar situations occur in hay fields cut too late in the season, prompting recommendations that the last cutting of hay should occur at least three weeks before the killing frost to enable plants to recover before winter, or swathing should wait until later in the season when cold temperatures prevent plants from expending stored reserves to fuel regrowth.

Few ranches, however, are able to stop grazing three weeks before the first killing frost in order to manage their livestock grazing enterprise as they do their hay enterprise. One approach that can help is to move livestock from rangelands to seeded pastures comprised of grass species that better tolerate grazing during early fall. If this is not feasible, another approach is to reduce grazing intensity during early fall. Grazing lightly during early fall (i.e., leaving more than three to four inches of residual forage height after grazing) provides grasses more leaf area for photosynthesis to produce energy that can restore the reserves used to break summer dormancy. Rotational grazing also works well during fall. The first grazing period can be brief during early fall when grasses are growing, followed by heavier grazing during late fall when it’s too cold for plants to initiate regrowth after grazing.

In summary, close grazing of range grasses during early fall can be very damaging when growing conditions have enabled grasses to break summer dormancy. Avoiding heavy grazing during these times will keep grasses healthy going into winter and help grasses produce more forage next spring. Happy ruminating.

In ranching it’s often necessary to spend money to make money. Funds from savings accounts or operating loans are spent to purchase inputs such as vaccine, seed, fertilizer, or feed. These inputs help fuel the engine that hopefully returns enough income to replenish the savings account or repay the bank, and also cover enough living expenses that you can afford to play the game again next year.

Range grasses often play a similar game during early autumn. Most years range grasses go dormant in late summer when days get hot and soils get dry. If more mild temperatures return in September and October accompanied by rain or early wet snow, grasses respond by breaking summer dormancy. To initiate this new growth grasses must draw upon stored energy reserves in their roots and stem bases. In other words, grasses must spend some of their savings to kick-start the new growth in early fall.

After the new leaves reach one-third to one-half their mature size they produce enough energy via photosynthesis to fuel their own growth and begin replenishing the plant’s energy reserves (i.e., begin repaying the bank). With enough time and leaf area, grasses are able to repay the bank, cover their living expenses, and can afford to play the game again next year. However, if grazing during early fall removes too much of this new leaf area before plants replenish their reserves, range grasses enter winter in a weakened condition, may not survive winter, won’t produce as much forage next spring, and won’t compete as well against weeds next year.

Similar situations occur in hay fields cut too late in the season, prompting recommendations that the last cutting of hay should occur at least three weeks before the killing frost to enable plants to recover before winter, or swathing should wait until later in the season when cold temperatures prevent plants from expending stored reserves to fuel regrowth.

Few ranches, however, are able to stop grazing three weeks before the first killing frost in order to manage their livestock grazing enterprise as they do their hay enterprise. One approach that can help is to move livestock from rangelands to seeded pastures comprised of grass species that better tolerate grazing during early fall. If this is not feasible, another approach is to reduce grazing intensity during early fall. Grazing lightly during early fall (i.e., leaving more than three to four inches of residual forage height after grazing) provides grasses more leaf area for photosynthesis to produce energy that can restore the reserves used to break summer dormancy. Rotational grazing also works well during fall. The first grazing period can be brief during early fall when grasses are growing, followed by heavier grazing during late fall when it’s too cold for plants to initiate regrowth after grazing.

In summary, close grazing of range grasses during early fall can be very damaging when growing conditions have enabled grasses to break summer dormancy. Avoiding heavy grazing during these times will keep grasses healthy going into winter and help grasses produce more forage next spring. Happy ruminating.

August 12, 2015 Comments are off Montana Stockgrowers Association
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Range Ruminations: Is “Take Half, Leave Half” a Good Way to Calculate Stocking Rate?

Jeff Mosley MSU ExtensionBy Dr. Jeff Mosley, MSU Extension Range Management Specialist

Former eastern Montana rancher and Past President of the Society for Range Management Dan Fulton once wrote, “Range, and particularly Great Plains range, cannot be rationally managed on the basis of range carrying capacity surveys. The only way to know for sure how many cows can run on it is by grazing cows on it.” Fulton’s statement reminds us that grazing management is a circle. We begin by observing the land and animals, and then make a plan based on what we have observed. Next we implement the plan and observe how well the plan is working. Based on what we observe, we make adjustments, observe again, make more adjustments, and so on. Grazing capacity surveys and stocking rate calculations can provide helpful estimates of an area’s sustainable stocking rate, and these ballpark estimates can be used to develop a plan, but they are not the final answer.

Stocking rate calculations include an estimate of proper utilization, and historically in Montana, the concept of “take half, leave half” (i.e., 50% utilization) has often been used. This approach recognizes that to remain healthy, grass plants must replace about 1/3 of their roots each year, and grass plants stop growing roots when more than 50% of their current year’s foliage is removed during the growing season. I believe 50% utilization is an appropriate threshold for growing-season grazing wherever most forage plants have similar palatability that results in relatively homogeneous levels of grazing among plants. However, I believe stocking rate calculations using 50% utilization provide stocking rates that are unnecessarily conservative in some situations and stocking rates that are unsustainable in other circumstances.

Situation #1. Grass plant response to grazing definitely depends on how much foliage is removed during the growing season, but plant response also depends on when the grazing occurs. Plants grazed later in the growing season can sustain 60-70% utilization if they have already had sufficient time earlier in the growing season to grow foliage, grow roots, and replenish energy reserves. Plants can sustain 80% utilization if grazing occurs when foliage and roots are not growing during winter plant dormancy.

Situation #2. Late spring/early summer is generally the time when grasses are most vulnerable to defoliation, but plant response to grazing also depends on how often grazing occurs. Grass plant health declines when 50% defoliation during late spring/early summer occurs for more than two successive years. Two years in a row is okay, but more than two consecutive years of moderate grazing during late spring/early summer is not sustainable. Some form of rotational grazing is necessary when moderate use occurs during late spring/early summer. A moderately stocked rotational grazing system that provides rest during late spring/early summer once every three years averages 33% utilization across the three years (50% use in Year 1 + 50% in Year 2 + 0% in Year 3 / 3 years = 33%). In this situation, stocking rate calculations should be based on 33% rather than 50% utilization.

Situation #3. Typically when utilization averages 50% on bunchgrass rangeland, many or most bunchgrasses have received heavy use (e.g., 70% utilization), a few bunchgrasses have received light use (e.g., 30% utilization), and a few bunchgrasses have remained ungrazed. Preferred bunchgrasses grazed during the growing season at 70% utilization are unable to grow roots and replenish energy reserves. Thus, some form of rotational grazing is necessary on bunchgrass rangeland grazed moderately during the growing season.

A 2-pasture rotational grazing system that provides growing season rest every other year averages 35% utilization for the preferred bunchgrasses over the 2-year period (70% use in Year 1 + 0% use in Year 2 = 35% utilization), which is safely below the 50% threshold. In this 2-pasture system, stocking rate calculations should be based on 25% utilization rather than 50% utilization (i.e., 50% in Year 1 + 0% in Year 2 / 2 years = 25% utilization).

Similarly, a 3-pasture rotational grazing system that provides growing season rest one year out of every three averages 47% utilization during the growing season for the preferred bunchgrasses over the 3-year period (70% use in Year 1 + 70% use in Year 2 + 0% utilization in Year 3 / 3 years = 47% utilization), again safely below the 50% utilization threshold. In this 3-pasture system, stocking rate calculations should be based on 33% rather than 50% utilization (i.e., 50% in Years 1 and 2 and 0% in Year 3, averaging 33% across the three years). This example also illustrates the incentive for 3-pasture versus 2-pasture rotational grazing systems. The 3-pasture system can be sustainably stocked 32% heavier than the 2-pasture system (i.e., 33% utilization – 25% utilization / 25% utilization = 32% increase).

In summary, stocking rate calculations can help inform grazing management planning and decision-making, but an area’s sustainable stocking rate can only be determined by making your best guess, implementing your plan, and then making adjustments as needed based on how the land and animals respond. Going forward, I suggest that initial stocking rate estimates will be more accurate and helpful when stocking rate calculations adjust the take half, leave half approach (i.e., 50% utilization) when needed, accounting for the time of year that grazing occurs, how often grazing occurs among years, and how much utilization levels vary among individual forage plants. Happy ruminating.

June 15, 2015 Comments are off Montana Stockgrowers Association
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Range Ruminations: How Much Grass Will I Have This Summer?

Jeff Mosley MSU ExtensionDr. Jeff Mosley, MSU Extension Range Management Specialist

Range forage growth this spring has been slow out of the chute in many parts of Montana.  My optimistic nature assures me, however, that plenty of rainfall and warmer temperatures will soon combine to ease my worries.  Those less optimistic souls among us might prefer to plan ahead using estimates of summer grass production.

Reliable estimates of summer grass production can be made by comparing this year’s amount of precipitation to the long-term average.  One method compares the amount of precipitation received in a “crop year”, while another method compares the combined total precipitation received in April, May, and June.

A crop year beginning 1 September and ending 30 June is appropriate for assessing precipitation effects on rangeland plant productivity in Montana.  For example, if precipitation during the crop year from 1 September 2014 to 30 June 2015 were to equal 80% of the 30-year average, then range forage production would likely be about 80% of normal in summer 2015.  Similarly, if the combined total precipitation received in April, May, and June 2015 were to equal 80% of the 30-year average for April + May + June precipitation, then range forage production would likely be about 80% of normal in summer 2015.

Either the crop-year precipitation method or the April + May + June precipitation method can also be used to help manage risk.  For example, if your area normally receives 4 inches of precipitation in April + May + June, and no moisture was received in April, you can examine long-term weather records to find how often your area received 4 inches in May + June alone.  The percentage of times this occurred in the past 30 years indicates the chances of it happening this year and the likelihood that summer forage production will be normal following a dry April.  Continuing the example, let’s say you receive 2 inches of precipitation in May.  You can then examine the long-term weather records to find how often your area received 2 inches in June alone.  The percentage of times this occurred in the past 30 years indicates the odds that your area will receive its normal 4 inches by the end of April + May + June and the likelihood that summer forage production will be normal.

Over the years I have used one or the other of these two precipitation methods to estimate summer grass production, and both methods have proven reasonably accurate.  These methods do not provide perfect estimates, of course, because they do not account for the many other factors that also affect range forage growth such as air temperature, humidity, and wind.  Both methods, however, provide useful ballpark estimates that can help you adjust livestock stocking rates, adapt pasture rotations, or make other management decisions.

Recently I encountered a situation that has convinced me to use both of these precipitation methods in tandem when making future estimates of range forage production.  I was reviewing the range forage growing conditions in summer 2014 on some foothill rangeland in west-central Montana.  Precipitation received in the 1 September to 30 June crop year of 2013-2014 was 17.3 inches, which was 25% more than the prior 30-year mean of 13.8 inches.  This figure alone might have led me to conclude that there was about 25% more range forage last year than normal.  But the combined total precipitation in April, May, and June 2014 was 6.2 inches compared with the prior 30-year mean of 7.1 inches, or 13% below average in 2014.

Overall, forage production in summer 2014 was not as great as the 25% above average crop-year precipitation indicated, but forage production was not as poor as indicated by the 13% below average April + May + June precipitation.  What happened?  Much of the above average precipitation in the 2013-2014 crop year was received in September 2013 and February and March 2014, and this stored soil moisture from fall, winter, and early spring helped offset the lack of rainfall during the prime late spring-early summer growing season.  Taken together the two estimates averaged 12% above normal, which matched very well with the actual amount of forage available in summer 2014.

If you don’t have precipitation records for your ranch, the Western Regional Climate Center has long-term data from hundreds of weather stations across Montana:  http://www.wrcc.dri.edu.  For assistance accessing these data, contact the Western Regional Climate Center, your local office of MSU Extension, or send me an email: [email protected].  Happy ruminating.