<![CDATA[ABSTRAK. Pemupukan sebaiknya didasarkan pada kebutuhan tanaman dan kesuburan lahan agar diperoleh hasil yang optimal. Adanya keragaman tanah dan lingkungan yang cukup tinggi di Indonesia menyebabkan kebutuhan pupuk berbeda dari satu lokasi ke lokasi lainnya. Penelitian bertujuan untuk mendapatkan dosis pupuk K optimum untuk dua varietas bawang merah pada status K-tanah yang berbeda. Metode penelitian terdiri atas survei status K-tanah yang dilakukan di sentra produksi bawang merah di dataran rendah Jawa Barat dan Jawa Tengah, dan percobaan pot yang dilakukan di Rumah Kasa Balai Penelitian Tanaman Sayuran Lembang dari Bulan Maret sampai dengan Desember 2008. Rancangan percobaan yang digunakan untuk percobaan pot ialah petak terpisah dengan tiga ulangan. Petak utama ialah bawang merah varietas Bangkok dan Kuning. Anak petak ialah status hara K-tanah, yaitu status K-tanah rendah (<20 ppm K2O), sedang (21–40 ppm K2O), dan tinggi (>41 ppm K2O). Anak-anak petak ialah dosis pupuk K terdiri atas 0, 60, 120, 180, dan 240 kg/ha K2O. Pupuk N (150 kg/ha) dan P (150 kg/ha P2O5) diberikan sebagai pupuk dasar. Hasil penelitian menunjukkan bahwa tidak terjadi interaksi antara varietas, status K-tanah, dan dosis pupuk K terhadap bobot kering tanaman, luas daun, hasil bobot umbi segar, dan bobot umbi kering eskip bawang merah. Namun serapan hara K tanaman dan residu pupuk K dalam tanah dipengaruhi oleh interaksi ketiga faktor tersebut. Hubungan antara hasil umbi bawang merah varietas Bangkok dan Kuning dengan dosis pupuk K pada semua status K-tanah bersifat kuadratik. Dosis pupuk K optimum untuk varietas Bangkok ialah 126,67 kg/ha K2O pada status K-tanah rendah, 170,00 kg/ha K2O pada status K-tanah sedang, dan 1,5 kg/ha K2O pada status K-tanah tinggi, sedangkan dosis pupuk K optimum untuk varietas Kuning ialah 214,29 kg/ha K2O pada status K-tanah rendah, 216,67 kg/ha K2O pada status K-tanah sedang, dan 106,50 kg/ha K2O pada status K-tanah tinggi. Hasil umbi dan serapan hara tanaman varietas Bangkok dan Kuning pada status K-tanah tinggi nyata lebih tinggi dibandingkan pada status K-tanah rendah dan K-tanah sedang. Makin tinggi status K-tanah dan dosis pupuk K, maka makin tinggi pula residu K dalam tanah.ABSTRACT. Sumarni, N, Rosliani, R, Basuki, RS, and Hilman, Y 2012. Effects of Varieties, Soil-K Status, and K Fertilizer Dosages on Plant Growth, Bulb Yield, and K Uptake of Shallots Plant. In order to get the optimum yield, fertilization should be based on plant need of nutrient and nutrient content of soil. The presense of high diversities of soil and environment in Indonesia cause the fertilizer needed are different from one location to another. This research methodologies were survey of soil-K status on some shallots production areas in lowland of West and Central Java, and pot experiment that was carried out at Screenhouse of Indonesian Vegetable Research Institute from March to December 2008. The aim of this experiment was to find out the optimum dosage of K fertilizer for two shallots varieties on several soil fertility level (soil-K status). A split-split plot design with three replications was used in this experiment. As main plots were shallots varieties, consisted of Bangkok and Kuning varieties. Subplots were the content/status of soil-K, consisted of low (<20 ppm K2O), medium (21–40 ppm K2O), and high (>41 ppm K2O). Sub-subplots were K fertilizer dosages, consisted of 0, 60, 120, 180, and 240 kg/ha K2O. N fertilizer (150 kg/ha N) and P fertilizer (150 kg/ha P2O5) were applied as basic fertilizers. The results showed that there were no interaction between varieties, soil-K status, and K fertilizer dosages on plant leaf area, plant dry weight, fresh and dry weight of bulb yield of shallots. But K uptake by shallots plant and residual of K fertilizer in soil were affected by the three those factors. The curves of the relationship between K fertilizer dosages and bulb yield of Bangkok and Kuning varieties on all soil-K status were quadratics. The optimum dosage of K fertilizer for Bangkok variety were 126.67 kg/ha K2O on low of soil-K status, 170.00 kg/ha K2O on medium of soil-K status, and 1.50 kg/ha K2O on high of soil-K status; whereas for Kuning variety were 214.29 kg/ha K2O on low of soil-K status, 216.67 kg/ha K2O on medium of soil-K, and 106.50 kg/ha K2O on high of soil-K status.The bulb yield and K uptake of Bangkok and Kuning varieties were significantly higher on high soil-K status than on low and medium of soil-K status. The more higher of K fertilizer dosages and soil-K status gave the more higher of K residual of K fertilizer in soil.]]>
