Effect of Mid‐ to Late‐ Season Water Stress on Sugarbeet Growth and Yield1

Abstract

AbstractCosts of irrigation (labor, water, and energy) and sometimes limited‐late‐season water are factors associated with the choice of crop and economic returns. Sugarbeets (Beta vulgaris L.) have shown certain tolerance to water stress, therefore the objective of this study was to evaluate growth rates and characteristics, sucrose accumulation, and N uptake by sugarbeets grown under mid to late‐season soil water deficit and plant water stress.Sugarbeets were grown in a field experiment on a Portneuf silt loam soil (Durixerollic Calciorthids; coarsesilty, mixed, mesic) under normal irrigation until 15 July, after which further irrigation was terminated or reduced on two treatments during a 2‐year period. Root yield, sucrose concentration, sucrose yield, plant N uptake, and petiole NO3‐N were determined from samples taken throughout each season. These experiments demonstrated that very little, if any, sucrose yield reduction can be expected in the Idaho area if irrigations are discontinued after filling the soil profile with water about 1 August and if the soil contains at least 200 mm of available water to a soil depth of 160 cm. During dry years, there may be an advantage to applying a light irrigation about 1 month after water cutoff and to have sufficient surface soil water present at harvest to prevent loss of roots by breaking. Use of deficit water management during August, September, and October curtailed leaf growth, reduced leaf area when no longer needed, reduced N uptake from the soil, increased sucrose concentration in the beet root, and decreased fresh root yield. These effects on yields were mainly caused by dehydration of the beet tops and roots so sucrose production was scarcely affected even though only 70% of the normal irrigation water was applied. Limited irrigations reduced evapotranspiration rates because of drier surface soil and partial stomatal closure, thereby decreasing the rate of water extraction from the soil reservoir by the plant. Use of mid to late‐season deficit water management could substantially reduce sugarbeet production costs in irrigated areas and economically benefit the consumer, producer, and manufacturer.