Oxidative treatment can isolate a stable organic matter pool in soils for process studies of organic matter stabilization. Wet oxidation methods using hydrogen peroxide are widely used for that purpose, but are said to modify poorly crystalline soil constituents. We investigated the effect of a modified NaOCl oxidation (pH 8) on the mineral composition of 12 subsoils (4.9-38.2 g organic C kg À1 ) containing varying amounts of poorly crystalline mineral phases, i.e. 1.1-20.5 g oxalate-extractable Fe kg À1 , and of different phyllosilicate mineralogy. Post-oxidative changes in mineral composition were estimated by (i) the determination of elements released into the NaOCl solution, (ii) the difference in dithionite-and oxalate-extractable Si, Al and Fe, and (iii) the specific surface areas (SSAs) of the soils. The NaOCl procedure reduced the organic C concentrations by 12-72%. The amounts of elements released into the NaOCl extracts were small ( 0.14 g kg À1 for Si, 0.13 g kg À1 for Al, and 0.03 g kg À1 for Fe). The SSA data and the amounts of dithionite-and oxalate-extractable elements suggest that the NaOCl oxidation at pH 8 does not attack pedogenic oxides and hydroxides and only slightly dissolves Al from the poorly crystalline minerals. Therefore, we recommend NaOCl oxidation at pH 8 for the purpose of isolating a stable organic matter pool in soils for process studies of organic matter stabilization.

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The addition of beneficial nutrients as silicon (Si) has become a concern in rice cultivation in some countries. However, it is not fully adopted in Indonesia. It is known that Si plays an important role on improving plant resistance on biotic and abiotic stresses. A pot experiment was conducted to study the response of rice plant growth on Si addition in Oxisols. A completely randomized design was set with eight treatments as varying Si rates (0, 100, 200, 300, 400, 500, 600 and 700 kg SiO2 ha−1) and three replications. Some variables were observed as plant height, number of tillers, stem strength, lodging resistance, biomass and yield components. Related to stem strength and lodging resistance, the observation was conducted prior to harvest. The results showed that initial soil Si available was 264 mg SiO2 kg−1 and categorized below the critical level. Si application showed significant effect on increasing number of tillers, stem strength, lodging resistance and the yield which occurred at 700 kg SiO2 ha−1 treatments. The rice yield increase by 34.66% at 700 kg SiO2 ha−1 treatments compared to control. This current result showed that addition of Si fertilizer has showed the effect on improving rice growth and yield in Oxisols.

The global demand for rice continues to increase due to population growth. In Indonesia, various innovations have been implemented for improving rice production, while magnesium silicate fertilizer application is still limited. The study was undertaken to investigate the effect of Mg and Si (MgSi Fert) on rice growth and productivity. This study was conducted at Luhur Jaya Village, Cipanas District, Lebak Regency, Banten Province in a rainy season. A randomized complete block design with ten treatments and three replications was set. The treatment was MgSi Fert with multiple dosages. Results showed that NPK fertilizer combined with 100 kg ha−1 MgSi fertilizer gave the highest yield. Based on the quadratic equation y = - 0.1301x2 + 28.812x + 5,474.2, it was known that highest slope on the equation was reached at dosage less than 150 kg ha−1 of MgSi Fert. The optimum dosage of MgSi Fert for Ciherang rice variety was achieved at 110 kg ha−1 with yield as 7.07 t ha−1. This present study showed that MgSi Fert application improved rice growth and yield.