Soil Carbon in Agroforestry Systems: An Unexplored Treasure?

Soil organic matter (SOM), which contains more reactive organic carbon (C) than any other single terrestrial pool, plays a major role in determining C storage in ecosystems and regulating atmospheric concentrations of carbon dioxide (CO2)^1^. Agroforestry, the practice of growing trees and crops in interacting combinations on the same unit of land^2^, primarily by resource-poor smallholder farmers in developing countries, is recognized as a strategy for soil carbon sequestration (SCS) under the Clean Development Mechanism (CDM) of the Kyoto Protocol^3^. The understanding about C storage and dynamics under agroforestry systems (AFS), however, is minimal. Our studies under various AFS in diverse ecological conditions in five countries showed that tree-based agricultural systems, compared to treeless systems, stored more C in deeper soil layers up to 1 m depth under comparable conditions. More C is stored in soil near the tree than away from the tree; higher SOC content is associated with higher species richness and tree density; and C3 plants (trees) contribute to more C in the silt- + clay-sized (<53 µm) fractions that constitute more stable C, than C4 plants, in deeper soil profiles4 - 8. These results provide clear indications of the possibilities for climate change mitigation through SCS in AFS, and opportunities for economic benefit - through carbon trading - to millions of smallholder farmers in developing countries

Optimum Population Size of Indigenous P-solubilizing Bacteria to Correct P Availability in Acid Soils

Indonesian acid soils were used to determine an optimum population size of indigenous P-solubilizing bacteria (PSB) for solubilizating fixed P. The experiment consisted of two sub-experiments. Sub-experiment I was to isolate the indigenous PSB from Ultisols, Fresh-water lowland Inceptisols, and tidal-swamp Inceptisols. Subexpriment II was to study the capacity of the isolated PSB to correct P availability in acid soils by inoculating the isolated PSB into the tested soils at 0, 105, 1010, and 1015 cells. The population of the indigenous PSB in the tested soils increased as a result of the inoculation. Both Al-P and Fe-P content in the three tested soils decreased as compared with the initial content. The increases of available P were significantly correlated with the decreases both in Al-P (r2 = 0.68 for the Ultisols; r2 = 0.51 for the fresh-water Inceptisols; and r2 = 0.35 for the tidal-swamp Inceptisols) and in Fe-P (r2 = 0.91 for the Ultisols; r2 = 0.45 for the fresh-water lowland Inceptisols; and r2 = 0.78 for the tidal-swamp Inceptisols). The increases of available P were significantly correlated with the increases of thepopulation of the PSB (r2 = 0.60 for the Ultisols; r2 = 0.55 for the fresh-water lowland Inceptisols; and r2 = 0.69 for the tidal-swamp Inceptisols). The available P in the three tested soils sharply increased if the population size of the PSB was about 1 × 109 cfu g-1 of soil

Documenting and modeling the accretion of surface and subsoil organic carbon in agricultural Inceptisols reclaimed from Mediterranean sea marshes in Sardinia

High input agriculture in productive Inceptisols that were reclaimed from sea marshes offers an opportunity to study the increase of soil organic carbon (SOC) in soils with originally low SOC. We documented the current SOC content and its distribution with depth for several soil profiles

Optimum Population Size of Indigenous P-solubilizing Bacteria to Correct P Availability in Acid Soils

Indonesian acid soils were used to determine an optimum population size of indigenous P-solubilizing bacteria (PSB) for solubilizating fixed P. The experiment consisted of two sub-experiments. Sub-experiment I was to isolate the indigenous PSB from Ultisols, Fresh-water lowland Inceptisols, and tidal-swamp Inceptisols. Subexpriment II was to study the capacity of the isolated PSB to correct P availability in acid soils by inoculating the isolated PSB into the tested soils at 0, 105, 1010, and 1015 cells. The population of the indigenous PSB in the tested soils increased as a result of the inoculation. Both Al-P and Fe-P content in the three tested soils decreased as compared with the initial content. The increases of available P were significantly correlated with the decreases both in Al-P (r2 = 0.68 for the Ultisols; r2 = 0.51 for the fresh-water Inceptisols; and r2 = 0.35 for the tidal-swamp Inceptisols) and in Fe-P (r2 = 0.91 for the Ultisols; r2 = 0.45 for the fresh-water lowland Inceptisols; and r2 = 0.78 for the tidal-swamp Inceptisols). The increases of available P were significantly correlated with the increases of thepopulation of the PSB (r2 = 0.60 for the Ultisols; r2 = 0.55 for the fresh-water lowland Inceptisols; and r2 = 0.69 for the tidal-swamp Inceptisols). The available P in the three tested soils sharply increased if the population size of the PSB was about 1 × 109 cfu g-1 of soil.Keywords: Al-P, Fe-P, fresh-water lowland, isolated, Pikovskaya medium, tidal swam

Identification of Predictors for Soil Water Retention of Indonesian Inceptisols

This study aimed to build a soil hydraulic properties digital database and to identify predictors for soil water retention of Inceptisols using data from developed database. Soil survey reports were compiled and soil hydraulic properties were entried into a spreadsheet. As many as 230 datasets of Inceptisols were extracted from developed database to identify predictors for soil water retention using Banin-Amiel and Stepwise techniques. Currently, the Soil Hydroulic Properties Digital Database strores 832 datasets from Central Kalimantan, East Kalimantan, Flores Island, Lombok Island, and Gorontalo District. The dataset is dominated by Inceptisols and fine soils. The correlation between soil water retention and other soil properties, and the order of predicting effectiveness varies with matrix potensial (pF) which influenced by soil moisture regime and pedogenesis type. Total pores and cation exchange capacity are potential predictors for soil water retention of Inceptisols in addition to particle sizedistribution, organic carbon, and bulk density. The Soil Hydraulic Properties Digital Database stores research results and provides data for any study regarding soil hydraulic properties. The dataset selection for developing pedotransfer function of Inceptisols should consider both soil moisture regime and pedogenesis type

Late Pliocene lakes and soils: a global data set for the analysis of climate feedbacks in a warmer world

The global distribution of late Pliocene soils and lakes has been reconstructed using a synthesis of geological data. These reconstructions are then used as boundary conditions for the Hadley Centre General Circulation Model (HadCM3) and the BIOME4 mechanistic vegetation model. By combining our novel soil and lake reconstructions with a fully coupled climate model we are able to explore the feedbacks of soils and lakes on the climate of the late Pliocene. Our experiments reveal regionally confined changes of local climate and vegetation in response to the new boundary conditions. The addition of late Pliocene soils has the largest influence on surface air temperatures, with notable increases in Australia, the southern part of northern Africa and in Asia. The inclusion of late Pliocene lakes increases precipitation in central Africa and at the locations of lakes in the Northern Hemisphere. When combined, the feedbacks on climate from late Pliocene lakes and soils improve the data to model fit in western North America and the southern part of northern Africa

Phosphate Adsorption Capacity and Organic Matter Effect on Dynamics of P Availability in Upland Ultisol and Lowland Inceptisol

Ultisols and Inceptisols were used to investigate the adsorption-desorption capacity of P and the effect of organic matter on the dynamics of P availability in tropical acid soils. The experiment consisted of two sub-experiments. Sub-experiment I was to study the adsorption-desorption capacity of Ultisols, Fresh-water lowland Inceptisols, and tidal-swamp Inceptisols. Therefore, surface soils (0 to 30 cm) of each tested soil were treated with 0, 10, 20, 30, 40, 60, 80, 100, 120, 140, 170, and 200 mg P kg-1 of soil. Sub-experiment II was to study the effects of organic matterapplication (0, 5, 10, and 15 Mg ha-1) on the dynamics of available P following 60d incubation under room temperature.P fertilizer application significantly affected water soluble-P (WSP) (pUpland Ultisol>fresh-water Lowland Inceptisol. OM application increased the BKP in all tested soils as compared to the control. Differences in pattern of soil available P dynamics over time were detected between upland soil and two lowland soils used in the current experiment.Keywords: Adsorption-desorption, Inceptisols, organic matter, Ultisol

PENINGKATAN KEMAMPUAN TANAH MENAHAN AIR DAN pH TANAH DENGAN KOMBINASI BIOCHARS DAN AMELIORAN KAPUR PADA INCEPTISOLS DENGAN INDIKATOR PADI GOGO

Karakter Inceptisols dengan great group berupa Psammentic (dominansi fraksi pasir pada tekstur tanah sampai kedalaman lapis olah 50 cm) adalah karakter porositasnya memiliki sebaran pori makro yang lebih mendominasi dibanding pori mikro sehingga kemampuan pengikatan air menjadi rendah, selain itu dijumpai fakta bahwa pH Inceptisols cenderung masam dan memiliki kandungan bahan organik yang relatif rendah. Peningkatan Kemampuan Tanah Menahan Air dan pH dengan Kombinasi Biochars dan Amelioran Kapur Pada Inceptisols dengan Indikator Padi Gogo bertujuan untuk mengkaji performa biochars limbah biomassa (bonggol jagung, sekam padi dan arang kayu) dikombinasikan dengan ameliorant kapur dalam meningkatkan Kemampuan tanah menahan air, nilai pH dan kandungan C-organik pada Inceptisols dengan menggunakan padi gogo sebagai indikator. Pengamatan yang dilakukan pada penelitian ini mencakup pengamatan kadar lengas secara gravimetri, pH secara elektrometrik, C-organik secara Walkey and Black dan Brangkasan kering padi gogo secara gravimetri. Rancangan percobaan menggunakan rancangan acak lengkap (RAL) atau completely randomized design (CRD). Analisis data menggunakan Fisher Test (Uji F) dengan taraf kepercayaan 95% apabila dijumpai pengaruh berbeda nyata maka apabila data normal akan dilanjutkan dengan uji lanjut berupa Uji Tukey dengan taraf kepercayaan 95%, namun apabila data tidak normal maka harus dinormalisasi menggunakan Krusskal Wallis. Penelitian ini diharapkan dapat mengatasi masalah Kemampuan Tanah Menahan Air, Bahan Organik dan pH pada Inceptisols. Kata kunci : Limbah biomassa, Biochars, C-organi

Dominant Soil Characteristics That Effect on Available K at Smectitic Soils

Research aimed to study dominant soil characteristics that effect on available K of smectitic soils were conducted in Laboratory of Research and Soil Test, Indonesian Soil Research Institute. The soil characteristics that has been analised were soil texture (pipette), organic-C (Kjeldahl), and CEC (NH4OAc); mineralogical analyses of clay fraction (X-Ray Diffraction); K fractionation: soil soluble-K (0.0002 M CaCl2), exchangeable-K (NH4OAc), and total-K (HNO3+HClO4); and potassium sorption. The results showed that the content of soil soluble, exchangeable, non-exchangeable, and total-K was in order of Vertisols > Alfisols > Inceptisols. The percentage of soil K fraction of the soils, however, was in order of soluble-K < exchangeable-K < non-exchangeable-K. Although the soils had high content in total K but most of them were in nonexchangeable form, thus they were not available for plant growth. Soil K buffering capacity and maximum sorption were in order of Vertisols > Alfisols > Inceptisols. The bond energy constant of Vertisols, however, was similar with that of Alfisols but it was about twice with that of Inceptisols. Soil clay, organic-C, and CEC affected the availability of soil K significantly (P > 0.95). Smectite contributed significantly (P > 0.95) to soil negative charge so that it held an important role in controlling soil K buffering capacity and maximum sorption. To increase the efficiency of K fertilizer, plant species that can produce organic acid exudated from roots in high quantity can be developed in smectitic soils. The use of Na, NH4, and Fe cations need also to be considered for K management in the soils as well