Abstract:
Objective To reveal the variation of potential evapotranspiration and crop coefficient of Vitex negundo L. var. heterophylla (Franch.) Rehd., for providing a basis for water resources management and vegetation construction of semiarid area.
Method Based on the lysimeter data, daily meteorological data, leaf area index (LAI) data and growth of new shoot length data from May to October in the year of 2021 in Henan Yellow River Xiaolangdi Earth Key Belt National Field Science Observatory, combined with the Penman-Monteith formula, the trends of potential evapotranspiration (ET0)and crop coefficient of Vitex negundo L. var. heterophylla (Franch.) Rehd. under abundant water conditions in different growth stages and their relationship with physiological growth indexes were analyzed.
Result (1) During the growth stage of Vitex negundo L. var. heterophylla (Franch.) Rehd., the ET0 value showed a downward trend. The ET0 value was higher in May and June, and began to decline after July. The total value of ET0 was 630.86 mm, and the daily average value was 3.43 mm·d−1. (2) The potential evapotranspiration during the growth period of Vitex negundo L. var. heterophylla (Franch.) Rehd. showed a parabolic trend. The potential evapotranspiration was the largest at blossom stage, with total value of 336.26 ± 18.19 mm and daily average value of 5.51 ± 0.30 mm·d−1, followed by fruiting stage and leaf unfolding stage, and the lowest value was found at defoliation stage with a total value of 41.57 ± 3.61 mm and a daily average value of 1.98 ± 0.17 mm·d−1, respectively. The total value of potential evapotranspiration during growth stage of Vitex negundo L. var. heterophylla (Franch.) Rehd. was 716.47 ± 40.21 mm, with a daily average value of 3.89 ± 0.22 mm·d−1. (3) LAI and new shoot length increased rapidly in May and June, and then the growth rate slowed down gradually. The maximum value of LAI reached its maximum value (2.93 ± 0.07) in August, then began to decline, and the minimum value was found in October, with the value of 1.63 ± 0.08. The growth of new shoots was the largest in May, 6.85 ± 0.25 cm, and basically stopped growing in October. (4) During the growth stage, the crop coefficient showed a parabolic trend, with the largest fruiting stage (1.45 ± 0.22), followed by blossom stage (1.25 ± 0.13), leaf unfolding stage (0.98 ± 0.05) and defoliation stage (0.95 ± 0.14) was the smallest, and the average of the whole growth stage was 1.28 ± 0.16. There was a significant positive correlation between crop coefficient and LAI (p < 0.01), with the coefficient of determination R 2 0.736, and there was no significant correlation between crop coefficient and growth of new shoot length (p > 0.05).