Irrigation scheduling methods for potatoes in the northern great plains

The successful irrigation of potatoes requires a knowledge of both irrigation application and scheduling methods. A four-year field study of four irrigation scheduling and application methods for Russet Burbank potatoes was undertaken on a sandy loam soil near Oakes, North Dakota. A randomized complete block statistical design was used to assess the influence of irrigation treatments on total yield, no. 1 grade yield, specific gravity and total irrigation applied. For the reference treatment, above-ground drip irrigation (AGDI) was used to apply irrigations based on 40% depletion of root zone available water on an area basis. The other treatments were. (1) AGDI, basing scheduling on a crop water stress index (CWSI) of 0.2; (2) subsurface drip irrigation (SDI), basing scheduling on measured soil matric potentials (SMPs) of 30 kPa using a feedback and control system to automate irrigation applications; and (3) AGDI, basing scheduling on SUBSTOR-Potatoes (SUBSTOR) growth model estimates of water use. Because of high relative humidity and intermittent cloudiness irrigations for the CWSI treatment were also scheduled based on SMP of 30 kPa at 0.3-m depth. Averages for yield (39.7 Mg ha(-1)), percentage no. 1 grade (76.1%), and specific gravity (1.086) did not differ between treatments. The reference treatment required an average of 220 mm irrigation water each year significantly higher than the 167 mm for CWSI, the 129 mm for SDI, and the 149 mm for SUBSTOR. Improved irrigation methods can save water without compromising potato yield or quality. Tensiometer-based methods were preferred, while SUBSTOR has limited practicality for irrigation scheduling.