Effect of Delaying Initial Irrigation on Cotton Using the Mobile Crop Water Use Application.

Cotton remains an important crop for the southeast Missouri producers even though number of acres fluctuate from year to year. However, the first irrigation of the season is often delayed to allow for pesticide application or other field operations. The objective of this experiment is to investigate the impact of those delays by using the Crop Water Use App (CWUA) and determine the effects on cotton to yield and rooting depth. The CWUA is a mobile irrigation scheduler that calculates daily ET (evapotranspiration) from a network of electronic weather stations located across Missouri.  Cotton was planted at two locations on loamy sand and silt loam soils. The Well-Watered (WW) treatment was irrigated when the CWUA showed the soil water balance was less than the manageable allowed depletion (MAD) % x available water holding capacity (AWHC) x rooting depth for the soil. Subsequently, when the next irrigation was needed, based on soil water deficit, the WW treatment and Delay 1 (D1) treatment were watered; continuing until Delay 3 (D3). From that point on everything was watered except for the control treatment.  Using soil moisture sensors the effectiveness of the rooting depth selected in the CWUA was monitored throughout the duration of the experiment. During the 2014 growing season it was identified that the CWUA is sensitive to soil texture and rooting depth. Ultimately, with this experiment we hope to quantify the importance of timely irrigation and offer a more mobile tool to help farmers schedule irrigations.