Pecan Orchard Irrigation and Alternative Watering Methods         Watering Pecan Trees
I've been known to say that both drip irrigation and utilizing a sprinkler system are the right way to water your pecan orchard.  I'll also tell you they're both the wrong way.  Just a year or so after I purchased our orchard, I looked out my front door and say an old man knelt down on the ground by one of my trees at the edge of the orchard digging in the dirt.  I scurried over toward him and stood over him awaiting some sort of explanation as to what exactly he was doing.  Without looking up or even introducing himself, he told me that my neighbor had consulted him about gopher problems and he had decided they were coming from my orchard.  As I watched him carefully set a trap, he declared gruffly, "These pecan trees won't never amount to nothin'.  You're using drip irrigation...they gotta have a sprinkler system."  I coaxed him to divulge his identity and discovered he owned a small five acre pecan orchard just down the road from me.  I had noticed the sprinkler system in his orchard and had caught myself admiring the condition of his trees from time to time as I drove past.  The brief conversation left me troubled about my drip irrigation for quite some time.  (Somewhere, someday, I'll tell you a funny story about this old man fighting an EMU that wondered up in his orchard.)
I began checking into sprinkler systems and found that they were just too cost prohibitive for our little operation.  I also determined that a sprinkler system would be somewhat insufficient and more costly to operate.  Between a third to half of the water used is lost to evaporation.  At least another third of the water is placed where the trees cannot utilize it, being in the middle of the tree rows, where tree roots cannot reach it.   I also concluded that irrigating the entire orchard would encourage insects to take up residence in the wet soil throughout the orchard and make weed control a huge undertaking.  Once I had accepted the fact that my drip system would have to suffice, I began contemplating how I could make it work.
The old man was right, and I knew it.  The way our system was set up, water was meant to trickle to all one hundred and something trees simultaneously.  It wasn't working.  Some trees watered well, while others received no water at all, especially those at the end of the orchard. 
I began my modification by removing the emitters from every
polyethylene lateral line running to the base of the trees.  I then cut the end off the line with a pocket knife.  I tested my modification and saw that many of the trees still did not receive water.
The previous owner had come up with an ingenious idea to deliver water to the orchard using the force of gravity.  He had constructed a 'water tower' above the well house, a tank holding 2500 gallons of water.  A cut-off valve controlled the flow to the orchard through a two inch PVC pipe which ran two feet below the ground.  At each row of trees, a one inch PVC pipe diverted water down the tree row.  The only flaw in the system was insufficient pressure to move the water back up to ground level through the 3/8 inch  polyethylene lateral line.
Armed with a plastic bag of PVC elbows, one inch PVC pipe,  ball valves, and a shovel, I set out one spring to overhaul my drip irrigation system.  I found the one inch pipe supplying each tree row and installed a cut-off at ground level.  This would enable me to water only one or two rows of trees at a time.   After completing my work, I tested the system, and with the new control valves in place and the ends cut off the poly lines, it worked like a charm. 
I can't claim to have a drip irrigation system.  It's more like a super-charged flood irrigation system, only we don't flood the entire orchard, just the immediate area around our pecan trees.  We have no water runoff, no wasted water, no wasted electricity putting water where it's not needed.  Our irrigation system is an energy efficient, natural resource concious, heck..in my opinion, it's the perfect irrigation system.
So the old man was partly right and partly wrong.  A drip irrigation system was obviously not going to do the job, but it didn't take a sprinkler system to make my pecan orchard thrive.
I don't consider myself to be necessarily ecologically minded, but I don't see the need to waste water.  At the same time I fully understand the importance of water to sucessful pecan production.  I also know that out here in west Texas that our trees won't survive if our underground water source is depleted.  Matter of fact, West Texas won't survive without water.  If you feel you are perhaps pulling more water out of the ground than necessary, if you're watering more dirt than trees, or if you're allowing a substantial amount of water to evaporate before it even hits the dirt...maybe you ought to to something about it.
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pecan orchard management
Maintaining a vegetation-free area at the base of your trees make harvest a breeze.