Tuesday, August 14, 2012

The fight for water

   We planted soybeans in our double-row intercrop study again this year. And for the first time, I've noticed that our young trees (11 years old) are starting to dominate over the intercrop. In the photo at left, you can see the perfect outline of the pecan tree root system's  area of influence. Soybeans were planted in the area that is now mostly bare soil (note the 7.5 inch planter rows) but the pecan tree out-competed the beans for water during this drought stricken growing season and the germinated soybeans died from a lack of water.
    I walked up the area in the bean field where the pecan tree's roots had their greatest impact and learned one more interesting thing. A huge soil crack has developed at the boundary between the pecan tree's root system and normal sized bean plants. This says to me that pecan roots are so efficient at extracting water from the soil that the soil has shrunk causing a crack in the soil.   
    This interaction between pecan trees and soybeans has got me thinking. Are the trees getting big enough for me to start thinking about seeding the entire field to a harvester-friendly covercrop?  Soybeans are bringing $16 per bushel: Can I pass up the economic opportunity of an intercrop while the trees are still producing less that 200 lbs. pecans/acre? All I know for certain is that the year to make the switch from intercrop to covercrop is coming soon. I just don't know if it will be 2013 or 2014. Most likely, a flood by the Neosho River will probably make that decision for me.