Abstract
We used a solar-adiation-controlled low-rate drip irrigation system developed by one of us for field culture of marguerite daisy (Argyranthemum frutescens). Groundwater is raised to more than 1 m above the ground by a solar-powered electric pump and is released slowly through low-rate drip irrigation tubes by gravity. The groundwater was nitrogen-rich, with a nitrate-N concentration of 5-30 mg L^<-1> (average 18 mg L^<-1>). We compared crop quality and nitrogen use efficiency etc. in two types of beds (0.75 m×30 m/ridge, 2〜3 ridges for each type): LI, with two low-rate (3.9 mL min^<-1> per hole or 20 mL min^<-1> m^<-1>) drip irrigation tubes; and CI, with a conventional-rate (300-400 mL min^<-1> m^<-1>) drip irrigation tube. The LI bed received 46 kg N ha^<-1> derived from the groundwater. Run off water in the LI bed was 33 % of that in the CI bed, and the amount of reached nitrate-N was 50 %. Plants absorbed more than 90 % of total N applied by fertilization and irrigation in the LI bed. The flower quality in the LI bed was superior to that in the CI bed because of the clear green leaves. The number of flowers that could be harvested earlier (i.e., by December), which earn a higher price, was greater in the LI bed than in the CI bed. In conclusion, this solar-radiation-controlled low-rate drip irrigation system delivering N-rich groundwater had better water and nitrogen use efficiency than the conventional system. This new system can contribute to water conservation by reducing fertilizer use and deriving N from groundwater.
