هیدرولوژی و ژئومورفولوژی ایران

اطلاعات کامل از علوم عمران و منابع طبیعیی (آبخیزداری،هیدرولوژی،ژئومورفولوژی ،آّب،خاک،گیاه)

Range readiness

Range readiness is a term frequently used by range managers. The Society for Range Management defines range readiness as “The defined stage of plant growth at which grazing may begin under a specific management plan without permanent damage to vegetation or soil.”  This definition says range readiness takes into account:

a). stage of plant growth;

b) .the management plan to be used; and

c) .permanent damage to vegetation and soil.

It does not consider economics, nutritive value of the forage or animal requirements.

In the early years of the range industry, horse and cattle grazed the grasslands year-long.  After some severe winters in the late eighteen hundreds it was accepted that hay was required for feeding of cattle during some winters.  Turnout of cattle on range occurred when the snow melted or hay supplied ran out.  Horses continued to graze year round and cattle continued to graze the grassland season-long until about the middle of this century.  The science of range management has been developing through the twentieth century.  Initially the objective was to develop management guides which would stop range deterioration and restore the range to its former productivity.  Two highly significant guides were developed:

1.       range utilization

2.       range readiness

 

Rules-of-thumb were provided for the application of these two guides.  The rule-of-thumb for range utilization was take half and leave half or 50 percent use.  The rule-of-thumb for range readiness was six to eight inches of new growth on bunch grasses.  These rules-of-thumb were intended to be applied on overgrazed ranges grazed season-long.  By applying these rules it was found that a gradual improvement in range condition took place.  By 1960 most of the range deterioration had been stopped.  Since that time considerable improvement has taken place. Much of that improvement can be attributed to the rules-of-thumb regarding range readiness and utilizationMuch of

Should we continue to manage for range improvement?  How much more range improvement can we obtain?  Does the old rule-of-thumb for range readiness still apply?  Obviously each piece of range needs to be examined for existing and potential productivity to determine if further improvement is practical or even possible.  Of greatest concern is whether the old rule-of-thumb still applies in today’s management.  The delay of grazing until there were several inches of new growth was designed to prevent grazing throughout the growing season. Today most of our ranges are not grazed all season.  Livestock are normally moved through a series of pastures in a rotation system so forage is able to grow through a portion of the season without any grazing.

Research has shown that grazing of bunchgrasses in the boot stage is more damaging than at any other stage of growth.  By delaying turnout on bunchgrasses until there is six to eight inches of new growth we are grazing it at the most critical stage of growth.  Studies at the Kamloops Research Station have shown that pinegrass responds similarly to bunchgrasses.  Grazing pinegrass early in the season during the rapid growth stage is less damaging than grazing it in July when growth is slowing down.  By following the old rule-of-thumb for range readiness we may actually be damaging our range under today’s grazing systems.  Range readiness may take place on your range a lot earlier than you thought.

Long-time Nicola Valley rancher Gerard Guichon once said, “We turn our cows out in March as soon as the snow is gone.”  He claimed their cows were a lot happier and calved easier on range due to the little bit of green grass and exercise.  He also claimed there were fewer disease problems on range and stressed the importance of having plenty of grass from the previous year.  One area of the ranch is reserved entirely for spring grazing and is fenced into several pastures which are grazed in rotation during the approximate three months spring grazing season.  By removing the cattle from the spring range at the end of May there is usually still some time for regrowth on even the last grazed pasture before summer dormancy occurs.  The Guichon ranch spring range has shown steady improvement for several decades under this management system.

Former Agriculture Canada Range Scientist, Dr. Dee Quinton once said that, “Range is not damaged by grazing it early but by the manner in which it is grazed.”  Repeated grazing of grass plants during the growing season, or pullout of plants, can seriously damage the grass.  The secret to prevention of damage is to keep the grazing season short during the growing season.  At least two pastures are required on grassland ranges for spring use before moving stock to the forest range.

Both research and experience show we can maintain or improve our ranges with early spring grazing.  We are fortunate to have both grassland and forest range in most of our ranching country with very different growing periods. Bunchgrasses may start growth early in March on the lower grasslands whereas at higher elevation in the forest the pinegrass does not start growth until May. Livestock should be moved into the forest as soon as rapid growth of pinegrass starts. This usually occurs very soon after the snow is gone.  By the time pinegrass is six to eight inches high its growth is starting to slow down and its nutritive value is dropping rapidly.  This is when maximum damage by grazing or clipping can occur.  Less damage will occur by grazing earlier.  Cattle should be on the highest elevation range available or north slopes, by early July.  By the end of July pinegrass growth will be slow, nutritive value of the grass will be falling rapidly and weight gain in calves and yearlings will also be slowing down.  Don’t waste nutritious forage – use it early!

 

 

 

 

+ نوشته شده در  چهارشنبه بیست و چهارم آبان 1385ساعت 7:34  توسط اسماعیل عبدالله وند  |