A study on watering methods for mangrove seedlings grown in nursery
การศึกษาวิธีรดน้ำแก่กล้าไม้ชายเลนในเรือนเพาะชำ
Noparat Bamroongrugsa, Assoc. Prof., D. of Biology, F. of Sci., PSU.
Pichit Kaewwongsri, Division of General Affairs, President's Office, Pattani Campus, PSU.
Corresponding e-mail : bnoparat@ratree.psu.ac.th
Grant : TRF
Presented : Regional Seminar for East and Southeast Asian Countries : Ecotone VIII,
Held in Ranong and Phuket Provinces, Southern Thailand, 23-28 May 1999
Key words : mangrove seedlings, saline water, salinity, acclimation, mangrove reforestation
The experiments were designed to study survival and growth rates of 3 mangrove species namely: Rhizophora apiculata, Bruguiera cylindrical and Ceriops tagal grown from popagules. Seedlings were planted in polyethylene bags filled with sandy soil and placed in a nursery. The plants were then treated with varying water application regimes. For the first trial, 3 types of water ie.
saline water (30 ppt), brackish water (12.5 ppt) and fresh water (0 ppt) were used. At 3 months after continuous water applications, the results showed that seedlings watered with saline water had less survival rates (46.6%) than those in brackish water (76.6%) and those in fresh water (95.0%) respectively. Among the seedlings, B. Cylindrica and C. tagal were more tolerant to brackish water
than R. apiculata. Similarly, seedlings grown under the fresh water regime showed greater plant
height with healthier appearance than those under the brackish or the saline water. As for the second trial, alternative and/or periodic watering between saline and fresh water were applied. It was found that, at 6 months after planing, R. apicalata had lower survival rates than B. cylindrica and C. tagal
when watered with continuous saline water for 5 days and then fresh water for 9 days. Similar survival rates were observed among the treatments when seedlings were watered with fresh water for 2 or 4 months continuousely and then saline water for a few days. In general, seedlings received occassional saline water showed greater growth than those under the long periods of solely fresh water. This findings suggested that using fresh water in the nursery planting was a benefit, particularly in avoid-ing salt accumulation in the bags. Occassional salinity from saline water might also be needed for
the seedlings to be acclimated to saline environment prior to outplanting as well as for some physio-logical processes.
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