The Importance of Irrigation Scheduling for Marginal Capacity Systems Growing Corn

Citation: Lamm, F. R., & Rogers, D. H. (2015). The Importance of Irrigation Scheduling for Marginal Capacity Systems Growing Corn. Applied Engineering in Agriculture, 31(2), 261-265. Retrieved from ://WOS:000353671300011Many irrigators in the Central Great Plains region do not use science-based irrigation scheduling for a variety of reasons, many of which are not strongly related to the technical feasibility. Evapotranspiration (ET)-based irrigation scheduling has been shown to be an acceptable irrigation scheduling method within the region. Many irrigators have expressed the rationale that there is no need to implement irrigation scheduling because their marginal capacity irrigation must be ran continually throughout the season to meet corn irrigation needs. ET-based irrigation schedules were simulated using 43 years (1972-2014) of weather data for Colby, Kansas, to determine irrigation needs as affected by irrigation capacity, center pivot sprinkler system application efficiency and the initial soil water condition at corn emergence. Adoption of ET-based irrigation scheduling with an initial soil water condition of 85% of field capacity and 95% application efficiency potentially could save on average 212 mm of water for a 25.4 mm/4 days irrigation capacity and 71 mm for a severely deficit 25.4 mm/8 day irrigation capacity. As application efficiency was decreased from 95% to 80% these savings for similar initial soil water conditions decreased from 176 to 67 mm for the greater and smaller irrigation capacities, respectively. Potential irrigation savings using an application efficiency of 95% were reduced but still appreciable when the initial soil water condition was 60% of field capacity averaging 154 and 25 mm for the 25.4 mm every 4 or 8 days irrigation capacities, respectively. Irrigators with marginal capacity systems should adopt science-based irrigation scheduling to make best use of their limited irrigation and should not discount their opportunity to save irrigation water even when their system restrictions are severe