ISHS Acta Horticulturae 644: International Symposium on Growing Media and Hydroponics
IRRIGATION TIMING: EFFECT ON PLANT GROWTH, PHOTOSYNTHESIS, WATER-USE EFFICIENCY AND SUBSTRATE TEMPERATURE |
| Authors: | S.L. Warren, T.E. Bilderback |
| Keywords: | irrigation volume, irrigation management, Cotoneaster dammeri ‘Skogholm’, leaching fraction. |
| Abstract:
Pine bark based container substrates, common in the southeastern United States, have low moisture retention properties; therefore, daily irrigations during the growing season are required to maximize plant growth. Current guidelines state that irrigation should occur during the early morning hours (before 1000 HR) to reduce potential of wind blowing the irrigation water from the targeted area and to reduce evaporation of irrigation water. However, limited research indicated that multiple application of water each day resulted in more growth compared to early morning application. The objective of these studies were to evaluate the effects of irrigation timing on plant growth and photosynthesis, water-use efficiency, and substrate temperature. In experiment 1, the daily total volume of irrigation to maintain 0.40 leaching fraction (LF) in the predawn application (0300, 0500, and 0700 HR) was divided into three equal parts and applied at the following times: 0300, 0500, and 0700 HR; 1200, 1500, and 1800 HR; 0900, 1200, and 1500 HR; and 0500, 1200, and 1900 HR. In experiment 2, the daily total volume of irrigation to maintain 0.15 LF within each treatment was divided into three equal parts and applied at the following times: 0200, 0400, and 0600 HR; 0600, 0900, and 1200 HR; 1200, 1500, and 1800 HR; and 0600, 1200, and 1800 HR. Irrigation applied at 1200, 1500, and 1800 HR produced 57% and 69% greater plant dry weight in experiment 1 and 2, respectively compared to irrigation applied following current guidelines (predawn). Root : top ratio was unaffected by irrigation timing. In both experiments 1 and 2, irrigation applied at 1200, 1500, and 1800 HR had higher water use efficiency compared to irrigation applied at 0300, 0500, and 0700 HR; and 0600, 0900, and 1200 HR. In experiment 2, plants irrigated at 1200, 1500, and 1800 HR maintained higher rates of net CO2 assimilation and had lower substrate temperatures from 1800 to 2200 HR compared to plants irrigated at 0300, 0500, and 0700 HR; and 0600, 0900, and 1200 HR. | |
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