1343 EFFECTS OF SEVERING OIL PALM ROOTS ON LEAF NUTRIENT LEVELS AND P UPTAKE EFFECTS OF SEVERING OIL PALM ROOTS ON LEAF NUTRIENT LEVELS AND P UPTAKE LIEW VOON KHEONG*; ZAHARAH A RAHMAN**; MOHAMED HANAFI MUSA** and AMINUDIN HUSSEIN** ABSTRACT Physical damage to oil palm roots affects the palm’s ability to acquire nutrients. In spite of this huge impact on the palm, the effects of root loss on palm nutrient status are unknown and this is unfortunate because optimal palm nutrient status is an important factor in fruit production. In trying to understand the effects of damage to the roots and the consequent effects on the palms, the impact of root damage was simulated by severing roots within 0%, 25% and 50% of the palm circle. Five months after the roots were severed, changes in leaf nutrient levels in the various treatments were observed. Each treatment was replicated fve times, using one palm per replicate. The impact of losing 25% of the roots within the palm circle changed the leaf K concentration and also the N:K ratio signifcantly (p < 0.05) compared with a loss of 50% of the roots within the palm circle. However, palms which lost 25% and 50% of the roots within the palm circle did not show any signifcant change (p> 0.05) in the N, P, Mg and B leaf concentrations compared to control. Further assessment of the impact of root loss on nutrient uptake by the palm, especially by the surviving tertiary roots, was made using 32 P isotope. Five surviving tertiary roots from each treatment were placed in contact with the 32 P solution, and the amount of isotope absorbed by the palms from the various treatments over a fxed time was measured. No difference in the amount of the isotope absorbed was observed. * D1 Oils Plant Science, Suite 1606, Arthaloka Building, 18 th Floor, J1. Jend. Sudirman kav.2, Jakarta, Indonesia. ** Department of Land Management, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor, Malaysia. E-mail: zaharah@agri.upm.edu.my The impact of a severe drought on FFB production in Southeast Asia in 1997 led to many studies on the subject over the ensuing two years. Caliman and Southworth (1998) and Foong (1999) reported on various aspects of the subject. Trying to protect the roots under drought conditions is diffcult especially when the only source of water, i.e. a river, dries up as well. As the soil gradually dries up, more roots would correspondingly die off too due to a lack of water and nutrients. The obvious implication of such a situation is a decline in the water and nutrient status of the palm, which will subsequently affect yield. Sometimes roots are infected and killed by diseases such as Ganoderma basal stem rot, water-logging, or mechanical injury inficted by equipment normally used in agricultural activities. Undoubtedly, the palms will eventually recover from the injuries unless the damage is too extensive and serious. The question then remains: how much damage to the roots could a palm sustain before INTRODUCTION It is believed that the larger root mass of palms planted in the more fertile inceptisols compared to the oxisols (Goh et al., 2004) may have been an important factor for the higher fresh fruit bunch (FFB) production in the former because the palms would have better chance of intercepting water and nutrients. It seems reasonable, therefore, to think that for palms planted on oxisols, the proliferation, preservation and effective functioning of their roots would be important if they are to have an equally high FFB production as those palms planted on the more fertile soil. Keywords: oil palm roots, nutrient uptake, root damage, 32 P isotope. Date received: 9 April 2010; Sent for revision: 2 July 2010; Received in final form: 28 November 2011; Accepted: 21 May 2012. Journal of Oil Palm Research Vol. 24 August 2012 p. 1343-1348 RESEARCH ARTICLES A-Zaharah.indd 1343 8/2/12 10:07 AM