Cotton Development and Yield Response to Irrigation, Planting Date, and Cultivar in North Carolina

In 2012, only 2.7% of North Carolina’s cotton (Gossypium hirsutum L.) was irrigated compared to the national average of 39%. The small size and nonuniform shape of most North Carolina fields are not conducive for a center pivot system. However, benefits to yield due to irrigation in North Carolina have been reported, specifically in years receiving below average or sporadic rainfall. The objective of this research was to investigate the impact of subsurface drip irrigation (SDI) on growth and yield of early- and late-maturing cotton cultivars at varying planting dates in eastern North Carolina. In 2014, the site received more than 750 mm of rainfall and no differences were observed for any parameters between irrigated and non-irrigated plots. Total rainfall in 2015 and 2016 was lower with several extended periods without rain events. There was a greater plant height increase and dry weight accumulation throughout the growing season in response to SDI. Cotton yields were increased by SDI in 2015 and 2016. Cultivar only influenced lint yield in 2016 with the earlier-maturing ‘PHY 333 WRF’ having greater lint yield than ‘PHY 499 WRF’. Planting date did not influence yield under irrigated conditions, and the timing of rainfall played a role similar to previous reports in North Carolina. Irrigation applied via SDI will increase cotton plant stature, fruit retention, and yield in response to deficit moisture conditions, independent of planting date or cultivar.