Effects of different irrigation regimes of drip irrigation under plastic film on sugar beet yield and water use efficiency

Abstract: In this study, we analyzed the effects of different drip irrigation regimes under plastic film on sugar beet yield and water use efficiency in Xinjiang of China. Drip irrigation under plastic film had been widely used in the arid areas of northwest China, especially in Xinjiang for saving water and fertilizer, increasing temperature of soil and preservation of soil moisture. The drip irrigation regimes of sugar beet under plastic film had a significant effect on increasing sugar beet root yield compared with traditional irrigation regimes. Two irrigation water quota (45 mm, 60 mm) and three irrigation frequency (eight, nine, ten) were combined to six treatments based on traditional drip irrigation regimes of sugar beet under plastic film in Xinjiang for suitable drip irrigation regimes under plastic film. The experiment was conducted during 2016 and 2017 at the Sugar Beet Improvement Center in Manasi, Xinjiang. The effects of different irrigation treatments on height and weight of sugar beet, leaf area index, root yield, sugar yield, percentage of sugar content, soil water content, evapotranspiration and water use efficiency were investigated. The water consumption of sugar beet was indicated combined with the soil water content and the suitable drip irrigation regimes under plastic film was proposed. The results showed that the increase of irrigation frequency could increase leaf area index, weight of sugar beet root and root yield, decreased percentage of sugar content and had no significant (P> 0.05) effect on evapotranspiration and sugar beet water use efficiency. The increase of irrigation water quota were not significant effect on leaf area index and percentage of sugar content, increased weight of sugar beet root and evapotranspiration and decreased water use efficiency of sugar beet. In addition, The SPAD value was decreased as the increase of irrigation water quota and irrigation frequency. By irrigation frequency and water quota interaction, the root yield of 45 mm and 60 mm irrigation water quota at frequency of eight were significant decreased, and percentage of sugar content and water use efficiency of 45 mm and 60 mm irrigation water quota at frequency of eight were decreased for the soil relative water content were under 50%. The soil relative water content was under 50% for 45 mm irrigation water quota at frequency of nine, and was more than 50% when 45 mm irrigation water quota at frequency of nine increased 15 mm. The weight of root yield was increased and root yield was increased by 7.4%-7.7% with the sugar yield increased by 9.4%-9.7% as the increase of 15 mm of 45 mm irrigation water quota at frequency of nine. The height of sugar beet, leaf area index were significant (P<0.05) higher than other irrigation frequencies for ten irritation frequency which the soil relative water content was more than 50%. The ten irrigation frequency was not significant (P>0.05) compared with nine irrigation frequency at 60 mm irrigation water quota, but the sugar yield of sugar beet was significant (P<0.05) less than nine irrigation frequency for 60 mm irrigation water quota. As increased 15 mm irrigation water quota for ten irrigation frequency at 45 mm irrigation water quota, the evapotranspiration was increased, the water use efficiency was decrease and root yield, percentage of sugar content and sugar yield of sugar beet had no significant difference. The results indicated that the nine irrigation frequency at 60 mm water quota was the suitable irrigation regimes of sugar beet under plastic film in Xinjiang for the lack of rain and sufficient sunshine, which saving 10% irrigation water compared with traditional irrigation regimes of sugar beet under plastic film.