EFEKTIVITAS BEBERAPA DEPOSIT FOSFAT ALAM INDONESIA SEBAGAI PUPUK SUMBER FOSFOR TERHADAP PERTUMBUHAN BIBIT KELAPA SAWIT PADA TANAH ULTISOLS

ABSTRAK Penelitian bertujuan untuk mempelajari pengaruh fosfat alam asalIndonesia terhadap kadar P dalam tanah dan pertumbuhan kelapa sawit.Penelitian dilaksanakan di rumah kaca Balai Penelitian Tanah di Laladon,Bogor dari bulan Juni sampai Desember 2009, dengan menggunakanrancangan percobaan acak kelompok dengan 8 perlakuan dan diulang 5kali. Perlakuan yang dicoba adalah 5 P-alam asal Indonesia, ditambahSuperphos, P-alam Tunisia, dan kontrol. Tanah yang digunakan adalahTypic Kanhapludults dan Typic Plinthudults yang diambil dari Lampung,dengan tanaman indikator adalah kelapa sawit. Hasil penelitianmenunjukkan bahwa pemupukan P nyata meningkatkan diameter batang,tinggi tanaman, berat akar dan berat kering tanaman. Pemupukan P denganSuperphos memberikan peningkatan yang lebih tinggi daripada pemu-pukan dengan fosfat alam. Efektivitas pupuk P-alam pada TypicPlintudults lebih rendah dibandingkan pada Typic Kanhapludults. PupukP-alam dari Indonesia sama efektifnya dengan P-alam Tunisia untukpemupukan tanaman kelapa sawit. Pemupukan P dengan Superphos padatanaman kelapa sawit nyata meningkatkan kadar P tanah lebih tinggidaripada kadar P tanah yang dipupuk P-alam. Pemberian pupuk P belumberpengaruh terhadap kadar P dalam akar dan tanaman kelapa sawit dalampembibitan. Kata kunci: Elaeis guinensis, kelapa sawit, tanah masam, fosfat alam ABSTRACT Effectiviness of several rock phosphate deposites fromIndonesia as P fertilizer sources on the growth of oilpalmseedling on ultisols The aim of this research was to study the effect of rock phosphatefrom Indonesia on P content on the soil and growth of oil palm. Thisresearch was conducted at the glass house of Indonesian Soil ResearchInstitute, Laladon Bogor from June to December 2009, using randomizedcomplete block design (RCBD) with 8 treatments and 5 replicates. Thetreatments were 5 types of Indonesia rock phosphate, Superphos, Tunisiarock phosphate, and control. The soils used were Typic Kanhapudults andTypic Plinthudults, and oil palm nursery as plant indicator. The resultshowed that P fertlizer was significant to increase trunk diameter, plantheight, root weight, and plant dry weight. Superphos fertilizer increasedtrunk diameter, plant height, root weight, and plant dry weigth better thanrock phosphate. Effectivity of rock phosphate at Typic Plinthudults waslower than at Typic Kanhapludults. Indonesian rock phosphate waseffective for fertilizing oil palm, as well as Tunisia rock phosphate. Pfertilization using Superphos significantly increased P soil content and wasbetter than rock phosphate. Application of rock phosphate did notinfluence P contents in root and plant of oil palm in nursery. Key words: Elaeis guinensis, oil palm, acid soils, rock phosphate