Sukristiyonubowo1 , Sofyan Ritung2 and Kusumo Nugroho2
Soils allocated for development of newly opened wetland rice fields in Indonesia can be from dry land or/and wetland to meet rice growing demand. The soils are low in major nutrient contents, but high in Fe concentration. The farmers do not apply N and K fertilisers’ bases on recommendation. The study was conducted on newly opened wetland rice farming originated from wetland in Tanjung Buka SP-2 village, Bulungan District, East Kalimantan Province, Indonesia in 2011. The aims were (1) to evaluate nitrogen and potassium input – out of newly opened wetland rice and (2) to validate the N and K recommendation. The results indicated that surplus N ranged from 39.03 to 71.62 kg N ha-1 season-1 , meaning the amount of urea is more than enough to replace N removed by harvest product. The recommended urea should be reduced to 150 kg urea with added compost of 3 tons ha-1 season-1. If the compost increased to 3 tons ha-1 season-1, K fertilizer can be increased to 150 kg KCl ha-1 season-1 to substitute K taken away by rice harvest product and to keep higher rice grain yield. These N and K recommendation rate imply the total urea and KCl available at district level with about 1,477 tons urea and 1,477 tons KCl district -1 season -1, respectively (150 kg urea x 9,849 ha and 150 kg KCl x 9,849 ha).
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