Study on the Evapotranspiration of Crisphead Lettuce by the Weighing Lysimeter

Weighing Lysimeter에 의한 결구상치의 증발산량 조사연구

This study was fulfilled by the weighing lysimeter method at the experimental farm of KonKuk University from April to June of 1986 to investgate the amount of evapotranspiration ( ET-lettuec )by the growing periods, evapotranspiration ratio, amount of watering per one time, days of intermission and soil moisture extraction pattern of the crisphead lettuce cultivated in the clay loam soil by different watering points of pFl.7, pF2.O, pF2.7. The results obtained are summar ized as follows : 1.The total evapotranspiration(ETlettuce) of the pFl.7 treatment plot was 358,9mm., 314.9mm in the pF2.O plot and 281.8mm in the pF2.7 plot, therefore the total ETlettuec increased with the difference of 33mm-44mm by the decrease of watering point. 2.The daily maximum ETlettuce by the watering points was 7.66mm, 6:54mm, 5.98mm, respectively in the last ten days of May, and the mean daily ETlettuce during the growing season by the watering points of pFl.7, pF2.O and pF2.7 was 5.44mm(384.5g), 4.77mm(337.2g) and 4.27mm(301.8g), respectively. 3.The evapotranspiration ratio showed maximum value in the middle of May which was the beginning of mid-season stage, and the mean evapotranspiration ratio during the total growing period was 1A7, 1.29, 1.15 by the watering points. 4.The days of watering intermission by the watering points of pFl.7, pF2.O and pF2.7 was 1.0day, 2.9days and 12.Sdays, respectively. 5.The yield of the crisphead lettuce by the watering treatments showed very high significance, and the pF2.O was confirmed as a optimum watering point. 6.The soil moisture extraction pattern(SMEP) of the pF2.0 treatment plot in the initial stage was 85.6% in the 1st and 2nd soil layer and 14.4% in the 3rd and 4th layer, and in the midseason stage, the moisture extraction proportion of the under layer accounted for 34.7%which showed that the root elongated to the lowest soil layer, and there was no difference of the SMEP between the mid-season and late-season stage. 7.The correlation coefficient between the ETlettuce and yield of lettuce by the three watering points was.739, which showed the significance of 5%.