PENGARUH PUPUK K TERHADAP PERTUMBUHAN, HASIL DAN MUTU RIMPANG JAHE MUDA (Zingiber officinale Rocs.)

ABSTRAK Kalium merupakan unsur hara yang paling banyak diserap oleh tanaman jahe dibandingkan N dan P. Produktivitas tanaman akan menurun apabila kekurangan unsur hara K, karena K mempunyai fungsi penting pada proses fotosintesis, aktifitas enzim, metabolisme karbohidrat, protein dan sebagai transport ion. Penelitian dilakukan di Kebun Percobaan Sukamulya sejak Januari sampai Mei 2010. Tujuan penelitian ini adalah untuk mengetahui pengaruh pemberian pupuk KCl terhadap pertumbuhan, hasil, serapan hara, dan mutu rimpang jahe muda. Perlakuan disusun dalam rancangan acak kelompok dan diulang 4 kali. Perlakuan yang dicoba terdiri atas delapan perlakuan pupuk KCl yaitu; 0, 50, 100, 150, 200, 250, 300, dan 350 kg/ha. Jarak tanam yang digunakan adalah 50 x 60 cm, dengan populasi 100 tanaman/plot. Contoh tanaman diambil pada umur 4 BST, sebanyak 5 tanaman setiap satuan perlakuan. Peubah yang diamati adalah, tinggi tanaman, jumlah anakan, bobot segar rimpang, bobot kering rimpang dan tanaman, kadar minyak atsiri, pati, serat, hara N, P dan K. Hasil penelitian menunjukkan bahwa tinggi tanaman, bobot segar rimpang, bobot kering batang+daun dan bobot kering rimpang meningkat secara nyata dengan meningkatnya perlakuan pupuk KCl. Tinggi tanaman, bobot segar rimpang, bobot kering batang+daun tertinggi dicapai pada perlakuan pupuk KCl dosis 350 kg/ha, masing-masing adalah 86,88 cm, 272,51 g/tanaman, dan 27,46 g/tanaman. Peningkatan bobot kering batang+daun dan bobot segar rimpang berkorelasi positif dengan meningkatnya pemupukan KCl sampai dosis 350 kg/ha, membentuk persamaan linier (r = 0,610 tn dan 0,643 tn ) dengan tingkat kepercayaan masing-masing P = 0,987** dan 0,99**. Kadar serat rimpang meningkat membentuk persamaan kuadratik (R 2 = 0,792*) dengan peningkatan pemupukan KCl sampai dosis 350 kg/ha, dengan tingkat kepercayaan P = 0,997**. Serapan hara N, P dan K berkorelasi positif dengan peningkatan pemupukan KCl sampai dosis 350 kg/ha. Serapan N membentuk persamaan linier (r = 0,541 tn ) dengan tingkat kepercayaan P = 0,977**, serapan P membentuk persamaan kuadratik (R 2 = 0,798*) dengan tingkat kepercayaan P = 0,992**, dan serapan K membentuk persamaan kuadratik (R 2 = 0,643 tn ) dengan tingkat kepercayaan P = 0,947**. Kata kunci : Zingiber officinale Rocs., pupuk KCl, pertumbuhan, mutu, hasil jahe muda ABSTRACT Potassium is the nutrient most absorbed by ginger compared to N and P nutrients. Crop productivity will decline if it lacks of K nutrient, because K has an important function in the photosynthesis of process, enzyme activity, metabolisms of carbohydrates and proteins, and it also functions as an ion transport. A study, conducted at Sukamulya Experimental Station from January to May 2010, aimed at determining the effect of KCl fertilizer application on growth, yield, nutrient uptake, and quality of young ginger rhizomes. Treatments were arranged in a randomized block design with four replicates. The treatments consisted of eight KCl fertilizer dosages, namely: 0, 50, 100, 150, 200, 250, 300, and 350 kg/ha. Planting space used was 50 x 60 cm, with plants population of 100/plot. Five plants per treatment unit were sampled at the age of 4 months after planting. Variables observed were plant height, number of tillers, rhizome fresh weight, dry weights of rhizomes and plants, contents of essential oil, starch, fiber, and N, P, and K nutrients. The results showed that plant height, rhizome fresh weight, stems + leaf dry weight, and rhizome dry weight increased significantly in line with the increase in KCl fertilizer dosages. The best results of plant height, rhizome fresh weight, and dry weight of stem + leaf were achieved at the highest dosage of KCl fertilizer (350 kg/ha). The measures were 86.88 cm, 272.51 g/plant, and 27.46 g/plant, respectively. Increase in dry weights of stem + leaf and fresh rhizome were positively correlated with increasing fertilizer dosages of KCl up to 350 kg/ha, forming a linear equation (r = 0.610 tn and r = 0.643 tn ) with P confidence levels of 0.987** and 0.99**, respectively. Increase in fiber content of rhizomes formed a quadratic equation (R 2 = 0.792*) by increasing dosages of KCl fertilizer up to 350 kg/ha, with a P confidence level of 0.997**. Uptakes of N, P, and K nutrients were positively correlated with increases in KCl fertilizations up to 350 kg/ha. Uptakes of N nutrient formed a linear equation (r = 0.541 tn ) with a P confidence level of 0.977**, P uptakes formed a quadratic equation (R 2 = 0.798*) with a P confidence level of 0.992**, and uptakes of K also formed a quadratic equation (R 2 = 0.643 tn ) with a P confidence level of 0.947**. Key words: Zingiber officinale Rocs., KCl fertilizer, growth, quality, young ginger rizhome