A study on the evapotranspiration from trellised Japanese pear [Pyrus serotina] orchard
1992
Nakayama, K. (Chiba Univ., Matsudo (Japan). Faculty of Horticulture) | Ichimura, T. | Kon, H. | Matsuoka, N.
Evapotranspiration from the trellised Japanese pear orchard was measured with some meteorological elements during May to November 1989. The meteorological elements were measured at the upper and lower parts of the pear trellis as shown in Fig. 1. The evapotranspiration was evaluated by measuring the transpiration from the young pear tree growing in plastic pot set on the same level as pear trellis and the evapotranspiration from the grass pot placed on the ground. The air temperature of upper part of the pear trellis was higher than that of lower part during the period from sunrise to around 14:00 at which the air temperature was maximum. During the night, this relation was reversed. The net radiation of upper part of the pear trellis was more than that of lower part. However, the difference in net radiation between both upper and lower parts of the pear trellis was decreased by the defoliation of the pear tree. The transpiration from pear tree was 2.4 mm/day on the average from June to August, followed by a gradual decrease. The evapotranspiration from grass surface under the pear trellis decreased from 4.7 mm/day at May to 1.7 mm/day at middle of November. The ratio (T/ET) of transpiration (T) from pear tree to evapotranspiration (ET) from the pear orchard increased with the increase in the leaf area index of the pear trellis. To find a simple method to estimate evapotranspiration from the trellised pear orchard, adaptabilities of Priestley and Taylor method and solar radiation method were examined. Although both methods can be used to estimate the evapotranspiration from the orchard, it was concluded that the parameters involved in these equations should be changed
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