Phosphorus fractions of paddy soils in Java, Indonesia

Paddy fields in Java contributes 52% of Indonesia's rice production. The use of fertilizers has been increasing significantly since intensification programs were started in 1969 for paddy fields in Java. Reports concerning phosphorus (P) fractions of paddy soils in Java is not available at present. Therefore, soils P fractions were investigated in Java paddy soils. Top soils from 23 locations were collected from the surface layer (0-20 cm) in February 2012. They consisted of 7 locations from West Java, 11 locations from Central Java and 5 locations from East Java. Selected physico-chemical properties and P fractions were analyzed in Laboratory of Graduate School of Life and Environmental Sciences, Kyoto Prefectural University Japan and Laboratory of Soil Chemistry and Fertility, Department of Soil Science and Land Resource, Faculty of Agriculture, Bogor Agricultural University respectively. The results showed that physico-chemical properties in West Java, Central Java and East Java were different. The mean values of Resin P (readily available to plant), in East Java was higher than that of Central Java and West Java. The mean values of NaHCO3-Psubi, -Psub0 and NaOH-Psub0 were comparable in West Java, Central Java and East Java. However, soil P accumulation in West Java, Central Java and East Java were different. Soil P in West Java was accumulated mostly in NaOH-Psubi and residual-P. Soil pH was negatively correlated with the NaOH-Psubi. The values of Fe extracted by ammonium oxalate (Fe sub0), Al and Fe extracted by dithionite-citrate-bicarbonate (Al subd and Fe subd), Al sub0 + 1/2 Fe sub0 can be used to predict the values of NaHCO3-Psubi-Psub0, NaOH-Psubi, -Psub0 fractions in Java paddy soils. Resin-Psubi was significantly correlated with NaHCo-Psubi and NaOH-Psubi suggesting that NaHCO3-Psubi and NaOH-Psubi can be used to predict the value of resin-Psubi. The different accumulation of P in West, Central and East Java needs attention in managing P fertilization.