Drought Tolerance Selection and Deficit Water Management for Sugar Beet.

Increased  water demands and drought have resulted in a need to determine if drought tolerance exists is sugarbeet lines and evaluate water management practices in sugarbeet production. Study 1 was conducted to determine if drought tolerance existed among a group of genetically diverse sugarbeet lines by evaluating sucrose yields over a range of water inputs levels. Study 1 was conducted over three consecutive growing seasons (2008-2010) at the NWISRL in Kimberly, ID on a Portneuf silt loam (coarse-silty mixed mesic Durinodic Xeric Haplocalcid) to assess the production of six KWS breeding lines and one commercial cultivar line under a range of water inputs [125% (W1), 100% (W2), 75% (W3), 50% (W4), and 25% of estimated crop evapotranspiration (ETc) and rain-fed (W6)] with water applied 3 times a week. There were differences in sugarbeet sucrose yield responses to water for the sugarbeet lines used in this study. The differences were demonstrated by comparing sugarbeet lines sucrose yields over the range of deficit water inputs using linear regression slope and intercept comparisons, drought stress index, and near maximum yield at the W2 water input level.  Greater drought tolerance or greatest difference in sucrose yield between lines was seen at the lowest water input treatment (intercept difference).  Linear regression analysis and drought stress index collaborated to show greater drought tolerance for KWS-05 compared to the commercial cultivar. There were also differences in overall yield potential among lines. Study 2 is determining best irrigation deficit water application timings for sugar beet.  Study 2 is being conducted from 2010-2012 at the NWISRL in Kimberly, ID on a Portneuf silt loam soil.  Irrigation treatments consist of end of season cumulative ETc water application rates of 100% (100% evenly throughout the growing season, 100% even), 60% (60% evenly throughout the growing season; 60% even), 60% (100% from emergence to end of June, 55% end of June to harvest; 60% early), 60% (rain-fed from emergence to end of July, 100% end of July to harvest; 60% late), 35% (35% evenly throughout the growing season; 35% even), 35% (100% from emergence to end of June, 25% end of June to harvest; 35% early), and 35% (rain-fed from emergence to mid August, 100% mid August to harvest; 35% late) and rain-fed (no irrigation, 8% ETc; rain-fed). All ETc percentages are based on non water stressed crop. Preliminary results from year 1 show that when deficit water inputs are applied, it is better to apply the water evenly throughout the season or supply 100% of ETc early then deficit irrigate later in the season. Sugarbeet with severe water stress early in the season (rain-fed) followed by 100% ETc later did not result in recovered yield potential.  Year 1 sucrose yield rankings were: 100% even > 60% even = 60% early > 60 late= 35 even = 35 early > 35 late = rain-fed.