The efficiency of potassium fertilization for soybean cultivation on vertisol and regosol

English. The effect of potassium application methods (broadcast and in rows application) and rice straw mulch application (burn and broadcast) on potassium efficiency on Vertisol and Regosol were evaluated in Ngawi and Lombok Tengah during dry season of 1993. The field experiment was arranged using a randomized complete block design, replicated four times for both locations. Combination treatments of site dressing of KCl (broadcast and in rows), dose of potassium (0, 30, 60, and 90 kg K2O/ha) and mulching application of rice straw (burn and broadcast) were assigned in factorial arrangement. Soybean cv. Wilis was planted in 4m x 5m plot, 40cm x 10cm planting distance, 2 plants/hill. Soil and plant analysis was done to know the extent of soil fertility and potassium absorption. The efficiency of potassium fertilizer on Vertisol at Ngawi and on Regosol at Lombok Tengah were considered low, namely 0,15 and 0,32 ton dry seed per 60 kg K2O, respectively. The highest seed yield was 1.72 t/ha, it was attained on Regosol at Lombok by application of 33,6 kg K2O/ha, placed in rows about 10cm distance from the plant rows. The efficiency of potassium on Vertisol and Regosol couldn't be increased by putting the fertilizer either in rows or broadcast and by mulching either broadcast or burning rice straw. The soybean gave some degrees of response to potassium fertilizer on Regosol with high content in K and Na, but poor in Ca

unknown. Peningkatan efisiensi pemupukan K di tanah Vertisol dan Regosol melalui cara penempatan pupuk KCl (sebar dan larik) dan pemberian mulsa jerami (sebar dan bakar) telah diteliti di Ngawi dan Lombok Tengah pada MK 1993. Percobaan menggunakan rancangan acak kelompok faktorial dengan empat ulangan. Perlakuan disusun secara faktorial: faktor pertama cara penempatan pupuk KCl (disebar dan dilarik), faktor kedua takaran pupuk K (0, 30, 60, dan 90 kg K2O/ha), dan faktor ketiga cara pengelolaan jerami (sebar dan bakar). Kedelai varietas Wilis ditanam pada petak berukuran 4m x 5m dengan jarak tanam 40cm x 10cm, 2 tanaman/rumpun. Analisis tanah dan tanaman dilakukan untuk mengetahui tingkat kesuburan tanah dan serapan K. Efisiensi pupuk K di tanah Vertisol Ngawi dan tanah Regosol Lombok Tengah relatif rendah, berturut-turut 0,15 dan 0,32 t biji kedelai per 60 kg K2O/ha. Hasil maksimum sebesar 1,72 t/ha di tanah Regosol Lombok Tengah diperoleh pada takaran pupuk 33,6 kg K2O/ha, yang diberikan secara larik dengan jarak 10 cm dari barisan tanaman. Efisiensi pemupukan K di tanah Vertisol Ngawi dan Regosol Lombok Tengah tidak dapat ditingkatkan melalui cara penempatan pupuk K (larik atau sebar) dan pemberian jerami (sebar atau bakar). Tanaman kedelai masih tanggap terhadap pemupukan K pada tanah Regosol yang kaya unsur K, Na, dan miskin Ca