Protecting pastures  

April 1, 2010

   Alfalfa has the ability to induce dormancy under drought conditions, said Steve Orloff, farm adviser and county director for the University of California cooperative extension in Siskiyou County. Grass, with a much shallower root, isn’t nearly as drought tolerant, he said.

   Orloff researched the effects of deficit irrigation and water curtailment in experiments at the Intermountain Research and Extension Center in Tulelake.  

   Alfalfa adapts

   “Fortunately, in the case of alfalfa, it is pretty well adapted to drought conditions,” he said. “Unless (drought) is really severe and continues for numerous years, you don’t lose stand and the plant survives.”

   Farmers’ yields will be affected by the amount of water and the soil type present in the field. Sandy soils will lose moisture faster than clay or loam soils, he said. Alfalfa’s deep taproots also can access groundwater in areas with a high water table, Orloff said.  

   However, in trials, grass yields suffered tremendously in the absence of water, he said.

   “In our tests at the field station, with alfalfa when we cut water off, and the earliest was June, we still had alfalfa to cut for first and even the last cutting,”   he said. “With grass, there was hardly anything to harvest. Once you shut the water off, it pretty much stopped growing.”

   How grass survives

   Different types of grass handle drought differently, with tall fescue being one of the more drought tolerant, followed by orchard grass. Both are more drought-tolerant than ryegrass and Timothy or Kentucky bluegrass. Depending on soil type, tall fescue can often survive a single year of drought, but stand loss often occurs in subsequent years if planted on sandy soils or with the less drought-tolerant species, he said.  

   For farmers and ranchers trying to protect the stand they already have, it is important to develop a management plan with a long-term outlook, said Chanda Engel, an Oregon State University extension forage and livestock agent.

   While it may be tempting to graze cattle on pasture lands to get some use of out the ground, Engel cautioned against overgrazing.

   “Different grasses have optimum stubble height, but a good rule of thumb is three to four inches,” she said. “The more leaf material you leave out there, the more quickly the plant can respond.”

   Engel said allowing more than half the plant to be grazed will end up causing long-term damage and impede root growth, which limits nutrient uptake and utilization of available water. If stand suffers too much, pasture owners will likely have to reseed their land at a cost of $200-300 an acre, Engel said.

   “One year of mismanagement can haunt you for several years in productivity,” she said.