A water-saving agricultural technology using passive underground watering and retaining moisture in residual roots

Research Project

Project/Area Number	22880011
Research Category	Grant-in-Aid for Research Activity Start-up
Allocation Type	Single-year Grants
Research Field	Irrigation, drainage and rural engineering/Rural planning
Research Institution	The University of Tokyo
Principal Investigator	DOI Ryoichi 東京大学, 大学院・農学生命科学研究科, 助教 (20587125)
Project Period (FY)	2010 – 2011
Project Status	Completed (Fiscal Year 2011)
Budget Amount *help	¥3,146,000 (Direct Cost: ¥2,420,000、Indirect Cost: ¥726,000) Fiscal Year 2011: ¥1,508,000 (Direct Cost: ¥1,160,000、Indirect Cost: ¥348,000) Fiscal Year 2010: ¥1,638,000 (Direct Cost: ¥1,260,000、Indirect Cost: ¥378,000)
Keywords	園芸作物 / 乾燥地 / 適正技術 / 土壌と地下水の保全 / 水資源 / 土壌環境保全 / 労力軽減 / 節水効果 / 乾燥ストレス / 土壌水分 / サバナ気候 / 半乾燥気候
Research Abstract	A basic study was conducted using horticultural crops (soybean and basil). A laboratory experiment of passive watering showed that the watering may realize the prevention of excessive surface watering thus contributes to conservation of soil environments by avoiding accumulation of salts on the uppermost soil layer and groundwater pollution. On the other hand, the quantitative optimization of the water supply was emerged as a technical issue. In the current watering technique, a smaller amount of water than that a crop requires may be given so as to result in the stress that affects yield, inter-organizational allocation of photosynthetic products, and the occurrence of negative physiological processes. Using soybean, a field experiment in Tunisia showed soil conservation effects in addition to minimization of labor were indicated. The experiment in Tunisia suggested that in the experimental period, the crop primarily utilized occasionally available rain water, while passive watering c … More ompensated for an amount of shortage of water as a result of consecutive dry days without rainfall. The above effects were planed to be investigated in the experimental field of the Asian Institute of Technology, Thailand. However, the experiment was ceased because the field was inundated due to the floodwater. By preparing soil columns, another laboratory experiment was made to observe water-retention by residual roots of crops. The density of crop root in the soil column was maximized by planting a leaf crop or soybean. The soil column was water-saturated then subjected to 50℃ incubation. The loss of water from the soil column with roots was not significantly different from that from the control which did not have roots. This insignificant difference was thought to be caused by narrow gaseous spaces created by and along the roots through which soil moisture was brought from the deepest layer to the soil surface, according to the observation of the structure in the soil columns prepared by putting the soil in a transparent plastic tube. Less