Assessment of drought stress tolerance of sugar beet (Beta vrulgaris L.) genotypes in furrow and tape irrigation systems

To evaluate sugar beet germplasm for identifying drought tolerant genotypes, precise methods are required for application of drought stress. A field experiment carried out as split arrangments in randomized complete block design with four replications in Karaj, Iran in 2007 and 2008. Main plots consisted of eight irrigation treatments with furrow and tape drip irrigation methods after 30 mm (except furrow irrigation) 80, 130 and 180 mm evaporation from the class A evaportation pan. Four sugar beet genotype; 7112, BP Karaj, BP Mashhad and BP Karaj (I13*A37.1) were randomized in sub-plots. The 30 mm level of tape drip irrigation was applied at two levels of %75 and %100 sugar beet crop water requirement. Combined analysis of variance showed that there was significant differences between irrigation treatments, for root yield, sugar yield and white sugar yield. The lowest root yield obtained in tape irrigation after 130 mm (41.2 t.ha-1) and 80 and 180 mm (41.7 t.ha-1) evaporation from calss A evaporation pan, respectively.  The highest root yield obtained in furrow irrigation after 80 and 130 mm (> 50.8 tha-1) evaporation from class A evaporation pan, respectively. Tape irrigation after 80 mm evaporation and furrow irrigation after 130 mm evaporation from class A evaporation pan had the lowest (6.35 t.ha-1) and highest (9.31 t.ha-1) sugar yield, respectively. Average water use in furrow irrigation after 80 mm evaporation from class A evaporation pan (common irrigation practice with 8-10 days interval) was 16000 m3.ha-1. However, average water use in drip tape irrigation after 30 mm evaporation from class A evaporation pan to meet 75% sugar beet crop water requirement was 7350 m3.ha-1. The highest and lowest irrigation water productivity belonged to drip tape irrigation after 30 mm (1.56 kgsugar.m-3) and furrow irrigation after 180 mm (0.42 kgsugar.m-3) evaporation from class A evaporation pan, respectively. Considering the results of this research, tape drip irrigation after 30 mm evaporation from class A evaporation pan with supplying 75% of sugar beet crop water requirement was identified as suiable irrigation system for application of drought stress for screening sugar beet germplasm.