Originally published May 17, 2013
Rainfall has been more than plentiful so far this corn growing season meeting water demands but important yield determining factors begin before tasseling. The number of kernels per row and kernel rows per ear begins to be determined between V6 and V8 as the ear shoots are formed. Much of the corn crop that emerged around March 15 is at or near V6(6th leaf collar visible).
Kernels per row will not be complete until about one week from silking which makes these vegetative stages important in final yield. Current Evapotranspiration(ET) rates(ET= transpiration or plant use + evaporation) for corn emerging around March 15 is 0.18 inches per day that will be increasing over the next few days to 0.20-0.23″ per day as daily high temperatures are predicted to increase to 89-91 degrees F. The most recent rain event in much of the area that brought soils back to Field Capacity or saturation was May 10, 2013.
Accumulated water deficits totaling 1.50″ – 2.00 ” should trigger irrigations depending on soil type and irrigation system. Furrow irrigated fields are: Macon Ridge Silt Loam/w hard pan & Sandy soils – 1.50″, Clay/Clay loams-1.75-2.00″ and Alluvial silt loams- 2.00″. Center Pivots: Macon Ridge silt loams/sandy soils-1.00-1.25, Clay/Clay loams 1.25″ and Alluvial silt loams; 1.50″.
Current irrigation scheduling I am conducting with local producers will require irrigations starting next week if no rain events occur. The last rain event on these farms was May 10 brought soils to Field Capacity or “0” inch deficit.
So far we have missed rains on 5/16/13 and 5/17/13. We will start irrigations on sandy soils/ridge soils Monday and alluvial silt loam soils a couple of days later. As wet as it has been, it may seem early to start irrigations but using this water balance approach accounting for all water added and daily ET rates is an effective way to be sure moisture demands are met starting with the first critical stages that help determine final yield starting at V6.
For more information about irrigation scheduling and/or ET rate charts contact:
County Agent, Richland Parish
The LSU AgCenter and the LSU College of Agriculture