Thursday, June 7, 2012


Rory Lewandowski, Extension Educator Wayne County and Crossroads EERA

            Pasture is an important component for many livestock enterprises.  Most of our common pasture forage species are classified as cool season species.  This includes bluegrass, orchardgrass, tall fescue, brome, timothy, white clover and alsike clover.  These forages grow best when there is adequate moisture, air temperatures in the 50 to 70 degree range and soil temperatures in the 50 to 65 degree range.  I bring this up because our current weather pattern and the extended forecast are definitely not bringing about conditions for optimum production.  In hot, dry conditions good pasture management is needed to keep cool season pastures productive.
When the weather is hot and dry it is critical that pastures not be overgrazed.  In grazing schools we talk about the “take half, leave half” principle.  In most cases, a good starting grazing height is 8 to10 inches of growth.  Remove animals from a pasture paddock when average pasture forage height is about 4 inches.  The remaining leaf area provides the “solar collector” surface that allows the photosynthetic process to keep going and to keep the plant growing.
 Studies have demonstrated that the percentage of top growth removed is correlated with root mass and growth below the surface.  When 50% of the top growth is removed the root mass and growth is only negatively impacted by a few percentage points.  However if 60% of the top growth is removed, the root mass is reduced by about 50%, significantly impacting the regrowth of the plant as well as nutrient and water absorption.  If 80% of the top growth is removed, the root system is shut down and essentially has to start growth all over.
In hot, dry weather leaving more plant cover is better.  In addition to keeping the photosynthetic process going and the root system fully functioning, that leaf cover acts like a mulch to keep the soil temperature cooler and reduce moisture loss from the soil.  This is important with cool season forage species when a few degrees difference in soil temperature could determine if the plant will go into dormancy or continue to grow.
Some pasture managers like to keep seed heads clipped off the grass plants to keep the plant in the vegetative state and produce higher quality forage.  I have often seen pastures clipped off at 2 to 3 inches in height.  During many of our typical springs with cool temperatures and good moisture the plant can handle this stress.  However, in hot, dry times it is more important to keep the plant residue so pasture managers may want to tolerate some seed heads or clip high at around 5 inches.
Hot, dry weather leads to slower pasture growth.  As grass growth slows down, the temptation is to speed up the pasture paddock rotation.  Actually just the opposite is needed.  When pasture growth slows down, pasture rotation must slow down to insure that each paddock has enough time to recover to a beginning grazing height of 8 to 10 inches.  The only way that this can be accomplished without staying too long in a paddock and overgrazing that paddock is to have multiple pasture divisions or paddocks.  To protect pastures and manage through hot, dry periods, the livestock owner needs at least 8 to 10 paddock divisions.
In order to keep cool season pastures productive the livestock manager must look ahead at pasture growth and keep an eye on extended weather forecasts.