1999 Fiscal Year Final Research Report Summary
System for Evaluating Environmental Factors Which Restrict Water Flow in Soil-Plant-Atmosphere-Continuum
Grant-in-Aid for Scientific Research (A)
|Allocation Type||Single-year Grants |
|Research Institution||IWATE UNIVERSITY |
HARA Michihiro Iwate Univ., Dept. Agron. & Forestry, Assoc. Prof., 農学部・農林生産学科, 助教授 (80003763)
HONJI Tsuyoshi Chiba Univ., Labo. Multi. Energy, Assoc. Prof., 園芸学部, 助教授 (60173655)
SHONO Hiroshi Iwate Univ., Dept. Agron. & Forestry, Research Assoc., 農学部・農林生産学科, 助手 (90235721)
INADA Ikuko Iwate Univ., Dept. Agron. & Forestry, Assoc. Prof., 農学部・農林生産学科, 助教授 (90110650)
OKUYA Akiko Yokogawa Denki Co., Ltd., Researcher, 環境システム営業本部, 研究員
|Project Period (FY)
1997 – 1999
|Keywords||Soil / Plant / Atmosphere / SPAC / Transpiration / photosynthesis / Diffusion resistance / Soil water tension|
Under the present research project, the following results and knowledge have been obtained and acquired.
1. Simultaneous measurements of transpiration and carbon-dioxide assimilation rates of tomato plants have been conducted with an apparatus for observing water flow in soil-plant-atmosphere-continuum (SPAC) . Results showed both the rates decreased remarkably according to the soil-water tension increase, while the ratio of the two rates remained constant. Daytime courses of vapor diffusion resistance between leaves and atmosphere showed J-shape increases, although the high resistance recovered lower during nighttime. It was concluded that soil-water tension larger than 400 cmHィイD22ィエD20 could be a restriction factor to water flow, however, increase of soil temperature from 15 to 25 ℃ remedied the restriction.
2. Characteristics of the rate of water absorption through root systems versus pressure have been tested. The results indicated that about 7 bar would be required for absorbing amount of water which was lost through the transpiration with the maximal rate, 740 mg/min.
3. Soil-moisture regimes (SMR) , which maintained soil moisture greater than 50% of container capacity (CC) , didn' t give serious stress to potted tomato, whereas those, which allowed soil moisture to decrease to less than 25% of CC, resulted remarkable yield loss.
4 . A theory has been developed to analyze relationships between water volumes and time observed with the so-called one-step outflow method. The new formula have been adopted to obtain water diffusivity of tested soils and justified.
5. Observations of salt affected soils have concluded that rhizomes of salt tolerant plants brought about increase in water permeability of soil, thus finally lead the improvement of salt leaching out of crop soil.
6 . In order to improve the leaching rates with placing coarser materials underneath the crop soil it was effective to make the boundary of two materials inclined.
Research Products (2 results)