2017 Volume 88 Issue 1 Pages 20-28
Subsurface drip fertigation (SDF) is a method of injecting liquid fertilizers through an irrigation system, which comprises a buried irrigation tube with earth piled on top. Here we examined the effects of SDF on Welsh onions by analyzing their growth and nutrient uptake. Because >45％ of the area under cultivation in Japan used to grow Welsh onions contains soil with an excessively high amount of phosphate, we examined the effects of subsurface drip irrigation (SDI) and SDF with a low-cost fertilizer application method using coated urea on such soil. 1) SDI enabled efficient and effective transition of soil moisture, enhanced the nitrogen utilization rate in the initial growth stage, and increased yield by 12％. 2) The use of liquid fertilizer in SDF resulted in significantly greater (by 13％) phosphate absorption in the hypothermic phase than did SDI. 3) Along with enhancing the nitrogen utilization rate, SDI using coated urea significantly increased the amount of phosphate absorption during all phases of growth and increased yield by 32–41％. 4) There was no significant difference in yield and nutrient uptake between SDF using coated urea effluent and SDI. These results indicate that the continuous supply of nutrients and water through SDF promotes utilization of phosphate accumulated in the soil, thereby contributing to enhanced growth and higher yields of Welsh onions.
