Arief Hartono

Transformation of added phosphorus to acid upland soils with different soil properties in Indonesia

Abstract The transformation of added phosphorus (P) to soil and the effect of soil properties on P transformations were investigated for 15 acid upland soils with different physicochemical properties from Indonesia. Based on oxide-related factor scores (aluminum (Al) plus 1/2 iron (Fe) (by ammonium oxalate), crystalline Al and Fe oxides, cation exchange capacity, and clay content) obtained from previous principal component analyses, soils were divided into two groups, namely Group 1 for soils with positive factor scores and Group 2 for those with negative factor scores. The amounts of soil P in different fractions were determined by: (i) resin strip in bicarbonate form in 30 mL distilled water followed by extraction with 0.5 mol L−1 HCl (resin-P inorganic (Pi) that is readily available to plant), (ii) 0.5 mol L−1 NaHCO3 extracting Pi and P organic (Po) (P which is strongly related to P uptake by plants and microbes and bound to mineral surface or precipitated Ca-P and Mg forms), (iii) 0.1 mol L−1 NaOH extracting Pi and Po (P which is more strongly held by chemisorption to Fe and Al components of soil surface) and (iv) 1 mol L−1 HCl extracting Pi (Ca-P of low solubility). The transformation of added P (300 mg P kg−1) into other fractions was studied by the recovery of P fractions after 1, 7, 30, and 90 d incubation. After 90 d incubation, most of the added P was transformed into NaOH-Pi fraction for soils of Group 1, while for soils of Group 2, it was transformed into resin-Pi, NaHCO3-Pi and NaOH-Pi fractions in comparable amounts. The equilibrium of added P transformation was reached in 30 d incubation for soils of Group 1, while for soils of Group 2 it needed a longer time. Oxide-related factor scores were positively correlated with the rate constant (k) of P transformation and the recovery of NaOH-Pi. Additionally, not only the amount of but also the type (kaolinitic) of clay were positively correlated with the k value and P accumulation into NaOH-Pi. Soils developed from andesite and volcanic ash exhibited significantly higher NaOH-Pi than soils developed from granite, volcanic sediments and sedimentary rocks. Soil properties summarized as oxides-related factor, parent material, and clay mineralogy were concluded very important in assessing P transformation and P accumulation in acid upland soils in Indonesia.

Phosphorus Sorption-Desorption Characteristics of Selected Acid Upland Soils in Indonesia

Phosphorus (P) sorption-desorption isotherms were studied in several acid upland soils developed from different parent materials in Indonesia. The soils varied in their chemical and physical properties. P sorption characteristics were satisfactorily described by the Langmuir equation, which was used to determine P sorption maxima and bonding energies. The soils varied widely in their capacity to sorb P. P sorption maxima ranged from 0.294 to 1.43 × 103 mg P kg−1 (mean 0.620 × 103 mg P kg−1) and bonding energies ranged from 0.64 to 9.00 L mg−1 (mean 3.42 L mg−1). The standard P requirements (P sorbed at 0.2 mg P L−1) ranged from 35 to 909 mg P kg−1 (mean 231 mg P kg−1). Parent materials affected the P sorption maxima and bonding energies. Soils developed from andesite and volcanic ash exhibited significantly higher P sorption maxima and bonding energies with a larger variability than the soils developed from sedimentary rock and volcanic sediments. Principal component analysis demonstrated that three principal components in Indonesian acid upland soils influenced P sorption, namely oxide-related factor (aluminum (Al) plus 1/2 iron (Fe) (by ammonium oxalate), crystalline Al and Fe oxides, cation exchange capacity, and clay content), acidity plus 1.4 nm mineral-related factor (exchangeable Al and 1.4 nm minerals) and organic carbon (C)-related factor (organic C and organically bound Fe). Stepwise regression demonstrated that the oxide-related factor was the main component actively contributing to P sorption maxima and bonding energies in these acid soils. It was demonstrated that the acidity plus 1.4 nm mineral-related factor led to the decrease of P sorption maxima. The organic C-related factor did not influence the P sorption maxima but decreased the P bonding energies. The results suggested that not only Al and Fe oxides but also soil acidity which is associated with exchangeable Al and 1.4 nm minerals of which smectite and vermiculite are common, should be included in models to estimate P sorption maxima in Indonesian acid upland soils. Furthermore, organic C content and organically bound Fe should be included in the models to estimate P bonding energies. Extraction with 0.01 mol L−1 CaCl2 led to a low soil desorbability of sorbed P (< 5%) and the desorbability was highly significantly correlated with the bonding energies during sorption.

Evaluation of nitrogen status of agricultural soils in Java, Indonesia

Abstract To evaluate the content of nitrogen (N) fractions of agricultural soils in Java, Indonesia, in relation to soil type and land use, 46 surface soil samples, 23 from paddy and 23 from upland, were collected throughout Java to include various types of soils. Soil N was separated into four fractions according to form and availability: inorganic extractable nitrogen (Iex-N), fixed ammonium nitrogen (Ifix-N), organic mineralizable nitrogen (Omin-N) and organic stable nitrogen (Osta-N). The total-N content was determined by the dry combustion method. The Iex-N content was determined by extraction with a 2 mol L−1 potassium chloride (KCl) solution and the Ifix-N content by extraction with an hydrofluoric and hydrochloric acid (HF-HCl) solution after removal of organic-N. The Omin-N content was evaluated as the potentially mineralizable N based on a long-term incubation method. The Osta-N content was calculated as the difference between the contents of total-N and the three other fractions. The total-N content was 2.06 g kg−1 on average. The contents of Iex-N, Ifix-N, Omin-N and Osta-N were 25.8, 99.1, 103 and 1,832 mg kg−1, respectively, and corresponded to 1.3, 4.8, 5.0 and 88.9% of the total-N. Hence, available (Iex-N and Omin-N) and stable (Ifix-N and Osta-N) fractions accounted for 6.3% and 93.7% of the total-N, respectively. Correlation analysis indicated that the contents of total-N and Osta-N had positive correlation with (Alo + 1/2Feo) as an index of amorphous minerals (p < 0.01), suggesting strong influence of volcanic materials for the accumulation of organic matter in Java soils. The content of Ifix-N had a positive correlation with nonexchangeable potassium (K) content (p < 0.01), suggesting the contribution of 2:1 clay minerals which can fix both ammonium (NH4+) and K+ in their interlayer sites. On the contrary, Omin-N did not have any significant correlation with soil properties, implying the importance of management for the improvement of the available N level in soils, rather than intrinsic soil properties. Soil N status further showed strong topographical trends depending on the elevation where soil developed. The contents of total N, Iex-N, Ifix-N, Omin-N and Osta-N in Java soils were on average 80, 69, 90, 65 and 80% of those in Japanese soils, respectively, suggesting that the soil N level in Java was lower than that in Japan, probably due to accelerated decomposition of organic matter, especially degradable fractions, reflecting high temperature, but that the level was relatively high for tropical soils due to the effect of volcanic materials. In conclusion, these results should be taken into account for the sustainable management of soil N in agricultural fields in Java, Indonesia.

Soil Acidification Patterns Under Different Geological and Climatic Conditions in Tropical Asia

Tropical forests are characterized by highly weathered and acidified soils, whilst patterns and processes of soil acidification are diverse under different geological and climatic conditions. To identify the dominant processes of soil acidification in Southeast Asia, proton budgets were quantified for plant-soil systems in Indonesia and Thailand. The net proton generation by plant uptake was consistently high in the tropical forests. Acidification of soils can function as nutrient acquisition strategies of plants that promote cation mobilization through mineral weathering and cation exchange reaction. Soil solution composition indicated that organic acids are dominant anions that drive acidification in the highly acidic soils from sandy sedimentary rocks. Production of organic acids in the O horizons can be enhanced by the high activities of fungal enzymes (peroxidases) especially in the lignin-rich and P-poor litters on the highly acidic soils. On the other hand, bicarbonate also contributed to cation mobilization in the moderately acidic soils from clayey sedimentary rocks and ultramafic rocks (Indonesia) and under monsoon climate with distinct dry season (Thailand). The spatiotemporal variation in fine roots (plant uptake) and organic and carbonic acids can lead to different pathways of pedogenesis, i.e., incipient podzolization (Al eluviation/illuviation) and ferralitization (in situ weathering). The differences in acid-neutralizing capacities of parent materials and climatic patterns can generate the variability in soil acidity, and plant and microbial feedbacks can further reinforce the patterns of soil acidification.

The Effect of Paraquat, Difenoconazole, and Butylphenyl Methylcarbamate (BPMC) on CO2 Emissions and Phenolic Acids in Peat Soil

Pesticides are widely used in agriculture, including on peat soil. The objective of this study was to analyze the effect of the application of paraquat, difenoconazole, and butylphenyl methylcarbamate (BPMC) on CO2 emissions and concentrations of phenolic acids in a peat soil. Peat soil sample was taken in District of Pulang Pisau, Central Kalimantan. The peat soil was applied with 1.89 mg kg-1 paraquat, 1.72 mg kg-1 difenoconazole and 1.65 mg kg-1 butylphenyl methylcarbamate (BPMC), then the soil was incubated for 1, 2, 4 , 5, 7, 10, 14, 21, 26 and 30 days. The results showed that the application of pesticides on peat soil increased CO2emission, and decreased CH4 emission and phenolic acid concentrations up to 30 days of incubation. The CO2 emmisions were derived from C of degraded pesticides and from C of phenolic acids, although the oxidation reaction was not accompanied by the change of soil pH.