Abstract
Experiments were conducted to clarify the mechanism of consumption of water storagein upland containing the more water in lower layers, and the evapo-transpiration which is the essential part of the consumption. A floating lysimeter in Fig. 1, was used. The results are:
1) The water for the maintenance of rapid crop growth lies in the range between moisture content 24 to 48 hours after irrigation and that around pF 3.2. If moisture content reaches pF 3.2 in the layer including more than 50% of root hair, the rapid crop growth will be hindered.
2) Evapo-transpiration changes mostly under the influence of meteorological factors within the moisture range mentioned above. The above results show that the value of moisture content to be considered for the planning of upland irrigation in Japan corresponds to the range of relatively low tention.
3) If shallow root crops are raised in soil layers containing the more moisture in lower layers, there exist tow different zones: the consumptive zone mostly consisting of root zone and the supplementary one several tens of centimeters under the, root zone. Moisture moves upward from the supplementary zone to the consumptive one about in proportion to evapo-transpiration. Such a supplementary water amounted about 50% of total evapo-transpiration in the experiment.
4) In the theory of soil moisture extraction pattern will not applicable the standard of the U. S. A., but also total readily available moisture estimated from the pattern will not show the true value if the measurement depth is not appropriate.
5) Based on the results, several methods were presented Shere to determine the total available moisture in the planning of upland irrigation in Japan.
