KADAR FOSFOR DAUN JARAK PAGAR (Jatropha curcas L.) DAN KORELASINYA DENGAN FOSFOR TANAH TERSEDIA DARI BEBERAPA METODE EKSTRAKSI

A. ARIVIN RIVAIE

Abstract


ABSTRAK
Percobaan untuk mengetahui kesesuaian beberapa metoda uji P
tanah untuk tanaman jarak pagar (Jatropha curcas L.) dan pengaruh
berbagai dosis pupuk P terhadap kadar P daun dan berat kering tanaman
terhadap jarak pagar telah dilakukan pada tanah Ultisol Citayam, Bogor.
Percobaan dilakukan di Rumah Kaca Balai Penelitian Tanaman Rempah
dan Aneka Tanaman Industri Pakuwon, Jawa Barat, dari bulan September
2006 sampai Juni 2007. Perlakuan terdiri atas dosis P (SP-36), yaitu 0, 50,
100, dan 150 mg P O
2 5 /kg tanah, yang disusun dalam Rancangan Acak
Lengkap (RAL) dengan empat ulangan. Hasil penelitian menunjukkan
bahwa kadar P daun dan berat kering tanaman jarak pagar meningkat
sejalan dengan dosis pupuk P yang diberikan. Peningkatan dosis pupuk P
juga diikuti oleh peningkatan kadar P tanah yang diekstraksi dengan
metoda Olsen-P, Bray-1 P, dan HCl 25%. Nilai-nilai kadar P tanah tersedia
yang diukur dengan ketiga metoda uji P tanah tersebut mempunyai hubungan yang nyata dengan kadar P tanah yang diekstraksi dengan determinasi (R 2 ) tertinggi ditunjukkan oleh persamaan regresi dari nilai-
nilai P tanah dengan metoda Bray-1 P (R 2 = 0.92) dibandingkan dengan
metoda Olsen-P dan HCl 25%, yang menunjukkan bahwa metoda uji
tanah Bray-1 P lebih sesuai untuk penyusunan rekomendasi pemupukan P
untuk tanaman jarak pagar di tanah Ultisol.
Kata kunci: Jatropha curcas L., P daun, metode uji P tanah, hubungan
antara P daun dan P tanah
ABSTRACT
A study was conducted to compare the suitability of several soil P
test methods for physic nut (Jatropha curcas L.) and to determine the
effect of various doses of P fertilizer on the leaf P content and the plant dry
matter on Ultisol Citayam, Bogor. The experiments were carried out in a
glasshouse from September 2006 up to July 2007. The employed
treatments, namely 0, 50, 100, and 150 mg P O
2 5 /kg soil (in form of SP-36),
were arranged in a Completely Randomized Design (CRD) with four
replications. The results showed that the leaf P content and plant dry
matter of physic nut on Ultisol increased in line with increasing doses of P
fertilizer applied. Increase of P fertilizer P rates was also followed by the
increase of soil P concentrations extracted by the three soil P test methods
(Olsen-P, Bray-1 P, and HCl 25%). The values of available soil P concentration measured by the three soil P test methods had significant relationship with leaf P contents. The highest coefficient of determination (R 2 ) showed by the regression equation of available soil P concentration
measured by the Bray-1 P (R 2 = 0,92) compared to those measured by the
Olsen-P and HCl 25% methods, indicated that the Bray-1 P method is
likely  more  suitable  to  be  used  in  establishing  P  fertilizer
recommendations for the physic nut in Ultisol.
Key words: Jatropha curcas L., leaf P, soil P test methods, relationship
between soil P and leaf P contents

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DOI: http://dx.doi.org/10.21082/jlittri.v20n3.2014.151-157

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