Friday, March 22, 2013

Pawnee kernels defects following 2012 drought

    Last fall, many of our Pawnee kernels developed dark blotchy spots in response to last summer's heat and drought. In looking over Pawnee samples provided by growers for this year's nut evaluation, I found a wide range in kernel appearance. The photo above illustrates these kernel defects. There are two kernel halves from each of four Pawnee samples.
    The two kernels in the lower left portion of the photo came from a well irrigated tree that I would consider "normal" in appearance. The kernels in the upper left position suffered the greatest drought induced color changes. These kernels are dark, covered in black blotches and have adhering kernel fuzz. These tree were not irrigated last summer.
    The kernels in the lower right position are less-intensely blotchy and slightly darkened. These kernels were produced by trees had a limited supply of water last summer provided by trickle irrigation. This nut sample points out one of the deficiencies of trickle irrigation in pecan orchards. Under severe drought conditions, many trickle systems can't provide enough water to totally eliminate water stress.
    The kernels in the upper right position illustrate a different type of kernel discoloration.  Rather than numerous small black blotches, these kernels have a large, uniformly-dark area centered on the eye of the kernel (the kernel eye is that area where one kernel half is attached to the other).  With this type of discoloration, the dark spot on underside of the kernel often larger that what appears on the upper side.
    Any type of kernel discoloration will reduce the marketability of pecan crop. A return to more normal rainfall patterns will greatly improve the kernel quality of Pawnee in future years.