Monday, October 15, 2012

Young trees suffer from Bermuda grass competition

Bermuda grass competes with young tree
     Bermuda grass is probably the most competitive ground cover commonly found in young pecan orchards. Try as you may to develop a weed free zone around young pecan trees; Bermuda grass will creep back, covering every inch of available soil. In the photo above, you can almost see where this pecan grower had sprayed glyphosate herbicide in a ring around his young tree. By early October, Bermuda had recovered the ground.

Light green leaves indicates low nitrogen
    Although all species of grasses are competitive with young trees, Bermuda is one of the toughest competitors for three reasons. Bermuda is a warm season perennial grass that actively competes with the tree for valuable summer soil moisture. Bermuda is also very aggressive in extracting nitrogen from the soil. In fact, the leaves on trees in this planting were light green indicating low leaf nitrogen levels (photo above).
    The third reason Bermuda grass is so competitive with trees is that it secretes allelopathic chemicals from its roots which suppresses the growth of other plants including pecan trees.  Once Bermuda grass is established in a pecan orchard it it very difficult to control. Only orchard wide and repeated applications of gylphosate seems to do the trick.
    I a twist of nature's irony, pecan trees will eventually win the war against Bermuda grass. Given enough time, pecan trees will grow so large as to completely shade out the low-light intolerant Bermuda grass.