Deficit Irrigation of Sugar Beets.

Increased water demands and drought have resulted in a need to determine the impact of deficit water management practices in irrigated sugarbeet production. Understanding the impacts of these alternative water management practices on production are needed to guide irrigation scheduling in water limiting situations. This study was conducted over two growing seasons (2011-2012) at the USDA-Agricultural Research Service, Northwest Irrigation and Soils Research Laboratory in Kimberly, ID on a Portneuf silt loam soil.  Eight irrigation treatments were compared using a surface drip irrigation system. The treatments consisted of end of season cumulative estimated crop evapotraspiration (ET_c) rates combined with application timing.  Treatments were: (1) 100% even - 100% ET_c evenly throughout the growing season; (2) 60% even - 60% ET_c evenly throughout the growing season; (3) 60% early - 100% ET_c from emergence to end of June, 55% ET_c from end of June to harvest; (4) 60% late - rain-fed from emergence to end of July, 100% ET_c from end of July to harvest; (5) 35% even - 35% ET_c evenly throughout the growing season; (6) 35% early - 100% ET_c from emergence to end of June, 25% ET_c end of June to harvest; and (7) 35% Late - rain-fed from emergence to mid August, 100% ET_c from mid August to harvest, and (8) rain-fed - no post emergence irrigation. All ET_c percentages were based on crop needs without water stress. Results showed that under deficit irrigation, higher yields were obtained when water was applied evenly throughout the season (even treatments) or 100% of ET_c  was applied early with deficit irrigation later in the season (early treatments). Sugarbeet with severe water stress early in the season (rain-fed) followed by 100% ET_c later (late treatments) had lower yield.