Yields and Sugar Content of Sugarbeets as Affected by Deficit High‐Frequency Irrigation¹

Abstract

Abstract Installation and operating costs of irrigation systems are related to system capacity and amount of water applied. If sprinkler systems can be designed for less than usual peak evapotranspiration rates, initial costs will be less. If less water is applied, operating expenses will decrease. Previous work indicated that sugarbeets can be grown satisfactorily under high‐frequency deficit irrigation (daily or more often at rates less than evapotranspiration) with soil water supplying part of the irrigation deficit. A field study was conducted, using solid‐set sprinklers, with the objective of determining the minimum amount of irrigation water that must be applied during peak use periods to avoid reduction in sugar yields. Treatments involved irrigation each morning at rates equivalent to various proportions of evaporation the previous day from a Class A Weather Bureau pan. The soil was near the upper limit of available water when the treatments were initiated. In 1974 yields of roots and sugar were not significantly different at daily irrigation rates equivalent to 100, 75, or 50% of pan evaporation. In 1972 and 1973 sugar yields were decreased only by not irrigating from mid‐August to mid‐September, compared to daily irrigation at 90% pan evaporation. Total water used by the crop was decreased by deficit high‐frequency irrigation while yield of sugar per unit of water used increased. In 1974 sugar yields per unit of water used increased from 184 to 264 kg/ha/cm as irrigation rates decreased from 100 to 50% of pan evaporation. This study indicates that with soils with adequate available waterholding capacity and crops that will tolerate deficit high‐frequency irrigation, systems can be designed for less capacity and total water application may be reduced. Soil water will be used to reduce the irrigation deficit.