IRRIGATION SCHEDULING METHODS FOR POPCORN IN THE NORTHERN GREAT PLAIN

Abstract

Irrigation of popcorn requires knowledge of methods of applying and scheduling irrigations. A four-year field plot study of four application-scheduling methods for popcorn was undertaken on a sandy loam soil near Oakes, North Dakota (ND), using a randomized block design. The study was designed to assess the influence of the methods on grain yields, popped volumes, and total irrigation water amounts applied for “White Cloud” popcorn. The reference method used aboveground drip irrigation (AGDI) to apply water and a scheduling method based on estimates of when 40% depletion of root zone available water (40% D) would be reached. The other irrigation application-scheduling methods were: AGDI and scheduling based on plant temperature, i.e., crop water stress index (CWSI) of 0.4; subsurface drip irrigation (SDI) and scheduling based on measured soil matric potential (SMP) of 30 kPa using a feedback and control system to automate irrigation applications through an SDI system; and AGDI and CERES-Maize (CM) growth model estimates of water use. Due to difficulties in implementing the CWSI method (high relative humidity and intermittent cloudiness), irrigations were also scheduled based on tensiometer-measured SMP of 40 kPa at 0.3-m depth for the CWSI treatment. Compared to the 40% D method, all other methods achieved statistically significant (0.05 level) irrigation water savings for popcorn without significant reductions in yields or popped volumes. Four-year average irrigation water amounts were 235, 134, 142, and 156 mm for the 40% D, CWSI, SDI, and CM methods, respectively, with corresponding popcorn yields of 4.63, 4.33, 4.44, and 4.47 Mg ha–1 and popped volumes of 26.3, 28.0, 28.3, and 28.0 L kg–1.