Irrigation Termination and Fiber Quality, Subsurface Drip Irrigation Versus Overhead

The standard practice is to terminate irrigation on cotton sometime between the first cracked boll and ten percent open boll.  This practice is typical to aid in the preservation of fiber quality.  However, the plant is typically still developing bolls on the upper part of the plant.  The availability of subsurface drip irrigation (SDI) and the adoption of SDI by producers has opened possibilities for continued irrigation after cotton bolls have begun to open. Studies have shown that additional irrigation after open boll will help to promote boll filling and increase yield over that of crops without the additional irrigation treatments.  Overhead irrigation can promote the degradation of fiber quality.  A two year study was performed at the Stripling Irrigation Research Park (SIRP) just outside of Camilla, GA.  Two varieties were planted in 2013 and three varieties in 2014.  The treatments and varieties were planted in randomized strips under pivot irrigation.  In coordination with the pivot irrigation, SDI was previously installed.  The crop was irrigated throughout the season following the University of Georgia (UGA) Modified Checkbook Method.  Once ten percent open boll was reached irrigation treatments were implemented.  The pivot was divided in half, overhead irrigation was stopped in half of the field and continued at a rate of one inch per week in the other half of the field.  SDI was started on the half of the field in which the overhead irrigation was stopped at a rate of one inch per week.  Preliminary results show that certain varieties have responded very well with additional yield to the extra SDI without fiber quality penalties.