Root and Sucrose Yields of Sugarbeets as Affected by Mid-to-Late-Season Water Stress

Investigations of the irrigation water requirement of sugarbeets (Beta vulgaris L.) in Arizona and California have shown that water stress several weeks before harvest of fall-planted beets reduces root yields but increases sucrose concentration (2,3). Their studies showed that, since soil and plant water stress late in the season did not significantly reduce sucrose production, irrigations could be discontinued 3 to 4 weeks before harvest for maximum water economy. Mid- to late-season water deficit studies on spring-planted sugarbeets at this Center in 1977 and 1978 clearly showed that sucrose yield was reduced very little in this area, if at all, if irrigations were discontinued after the soil profile was filled with water about 1 August or 10 to 12 weeks before harvest, on soil having a useable soil water reservoir of at least 200 mm (1) . However, if no rainfall occurs, a light irrigation about 1 month after water cutoff may be advantageous. The major difference between these two areas (Arizona-California and Idaho) is that in Arizona and California, potential evapotranspiration rates are higher and increasing when fall-planted beets are harvested; whereas in Idaho, potential rates are lower and decreasing when spring-planted beets are harvested. Allowing mid- to late-season water stress to develop in the Idaho area reduces irrigation water requirements by about 30% during August, September, and October when irrigation water and hydro-electric power for pumping are in shortest supply. Other recent investigations also show the drought tolerance of sugarbeets throughout the growing season ( 8, 11)