Effect of drip irrigation frequency on radish (Raphanus sativus L.) growth and water use

Irrigation frequency is one of the most important factors in drip irrigation scheduling, and a proper irrigation frequency can establish moderate moist and oxygen conditions in the root zone throughout the crop period. Field experiments on the effects of irrigation frequency on radish growth and water use were carried out in 2001 and 2002. The experiment included six irrigation frequencies: once every day, once every 2 days, once every 3 days, once every 4 days, once every 6 days and once every 8 days. There was no significant difference among the six treatments on radish development and yield, but significant differences in radish roots distribution and market quality were found. Radishes irrigated once every 3 days had well-developed roots throughout the crop period, the lowest cracking rate and the least number of radishes of Grade 3. The observation results of lysimeter in 2002 showed that radish evapotranspiration decreased as irrigation frequency decreased, and the general changing tendency of 2-day ET of high irrigation frequency was related to that of 2-day evaporation. It is recommended that radish irrigation frequency should be once every 3 days and the irrigation amount should be estimated according to the evaporation of 20 cm diameter pan in the North China Plain.