EFFECT OF ROOT-WRENCHING AND CONTROLLED WATERING ON GROWTH, DROUGHT RESISTANCE AND QUALITY OF BARE-ROOTED SEEDLINGS OF <em>ACACIA</em> <em>MANGIUM</em>

Abstract

The possibility of conditioning and hardening barerooted Acacia mangium seedlings by root wrenching and controlled watering was
investigated. Ten-week-old seedlings in open beds were subjected to combined treatments of three root wrenching regimes (unwrenched, wrenched fortnightly, wrenched monthly) and two watering regimes (once every three and six days). Potted seedlings with daily watering were used as controls. Twelve weeks later, the seedlings were assessed for dry matter production, root/shoot ratio, root growth capacity, diameter and height growths, diameter/height ratio, water relations and survival. Root wrenching and controlled watering had significant effects on most of the growth parameters. Good survival was associated with high root/shoot ratio, diameter/height ratio, root growth capacity and efficient water economy. Good was observed in seedlings watered every six days and wrenched either monthly or fortnightly. Control seedlings which had high shoot development but low root growth capacity and poor water economy showed low survival rates. Unwrenched bare-rooted seedlings watered every three days had poor survival compared to unwrenched seedlings watered every six days. Monthly wrenched seedlings had only slightly better survival results than fortnightly wrenched seedlings, indicating that increased frequency did not necessarily improve survival. A combination of monthly wrenching and 6-day watering is recommended.