Source and Accumulation of Soil Carbon along Catena Toposequences over 12,000 Years in Three Semi-Natural Miscanthus sinensis Grasslands in Japan

Miscanthus-dominated semi-natural grasslands in Japan appear to store considerable amounts of soil C. To estimate the long-term effect of Miscanthus vegetation on the accumulation of soil carbon by soil biota degradation in its native range, we measured total soil C from the surface to a 1.2 m depth along a catena toposequence in three annually burned grasslands in Japan: Kawatabi, Soni, and Aso. Soil C stock was estimated using a radiocarbon age and depth model, resulting in a net soil C accumulation rate in the soil. C4-plant contribution to soil C accumulation was further estimated by δ13C of soil C. The range of total soil C varied among the sites (i.e., Kawatabi: 379–638 Mg, Soni: 249–484, and Aso: 372–408 Mg C ha−1). Catena position was a significant factor at Kawatabi and Soni, where the toe slope soil C accumulation exceeded that of the summit. The soil C accumulation rate of the whole horizon in the grasslands, derived C mainly from C4 plant species, was 0.05 ± 0.02 (Average ± SE), 0.04 ± 0.00, and 0.24 ± 0.04 Mg C ha−1 yr−1 in Kawatabi, Soni, and Aso, respectively. Potential exists for long-term sequestration of C under M. sinensis, but the difference in the C accumulation rate can be influenced by the catena position and the amount of vegetation.

Distribution of organic carbon in Ultisol soils with citronella and pine vegetation, at Gayo Highlands, Aceh

Soil organic matter is an indicator of soil fertility. The purpose of this study was to analyse various forms of soil organic carbon in citronella plantation, citronella plantation under pine tree, and soil under pine tree. Soil organic carbon in various forms was analysed from soil samples taken from each horizon and soil profile. The soil profiles observed were ultisol profiles planted with citronella, citronella under pine tree, and under pine tree, and slopes; 0-8%, 8-15%, 15 -25%, and 25-40%, in order to obtain 12 soil profiles with a total of 39 soil samples. Ultisols planted with citronella had higher soil organic carbon than ultisols planted with citronella under pine tree and ultisols under pine trees. Based on the slope, the highest soil organic carbon was obtained in the soil with a slope of 0-8%, and decreased with increasing slope. Based on soil depth, the highest soil organic carbon was obtained in the upper horizon, compared to the horizon below. The highest total soil organic carbon was obtained at the soil surface horizon with a slope of 0-8% and citronella was planted. This pattern of total soil organic carbon is similar to that of sesquioxide bound organic carbon, but is not consistent with that of free clay bound organic carbon.

Aplikasi pupuk hayati ameliorant, dan pupuk NPK terhadap N total, P tersedia serta pertumbuhan dan hasil jagung pada inceptisols

Inceptisols umumnya memiliki tingkat kesuburan tanah rendah sampai sedang. Upaya peningkatan ketersediaan hara tanah Inceptisol dengan pupuk anorganik NPK perlu diimbangi dengan aplikasi pupuk hayati dan amelioran organik. Percobaan ini bertujuan untuk mengurangi dosis pupuk NPK dengan menggunakan pupuk hayati dan amelioran organik serta meningkatkan hasil tanaman jagung. Percobaan dilakukan di Pasir Banteng, Kabupaten Sumedang. Penelitian menggunakan RAK faktorial. Pupuk hayati dengan amelioran organik sebagai faktor pertama sebanyak empat taraf: tanpa pupuk hayati dan amelioran (kontrol), diberi pupuk hayati, amelioran organik, dan gabungan keduanya. Faktor kedua yaitu dosis pupuk NPK empat taraf: 100%, 80%, 60%, 40% NPK dosis anjuran. Dilakukan tiga kali ulangan. Hasil penelitian menunjukkan terdapat interaksi antara pupuk hayati, amelioran organik, dengan pupuk NPK terhadap tinggi tanaman, N-total tanah, bobot tongkol berkelobot dan tanpa kelobot. Pemberian pupuk hayati dan amelioran disertai pupuk NPK 100% dan yang tanpa diberi amelioran menghasilkan bobot tongkol tanpa kelobot sebesar 1.089 g dan 1.064 g per tanaman. Pemberian pupuk hayati dengan amelioran dan pemberian pupuk NPK 100% menghasilkan bobot pipilan per tanaman 526,08 g dan 539,08 g. Aplikasi pupuk hayati dan amelioran organik belum mampu mengurangi dosis penggunaan pupuk NPK pada Inceptisols asal Pasir Banteng. Inceptisols generally have low to moderate soil fertility. The effort to increase the nutrients availability in Inceptisol through the application of NPK fertilizers need to be balanced with biofertilizers and organic ameliorants. This experiment aimed to reduce the dose of NPK fertilizer by using biofertilizers and organic ameliorants and to increase maizeyields. The experiment was conducted in Pasir Banteng, Sumedang Regency. The factorial RBD was used. The biofertilizer with organic ameliorant as the first factor: no biofertilizer and no ameliorant (control), biofertilizer, organic ameliorant, and combination of both. The second factor was dose of NPK fertilizer: 100%, 80%, 60%, 40% of recommended NPK dose. It was repeated three times. The results showed that there was interaction between biofertilizer, organic ameliorants, with NPK fertilizers on plant height, N-total soil, weight of cobs with and without husk. The application of biofertilizer and ameliorant with 100% NPK fertilizer and without ameliorant were 1,089 g and 1,064 g of cobs without husks, respectively. The application of biofertilizer with ameliorant and 100% NPK fertilizer had a grain weight of 526.08 g and 539.08 g, respectively. The application of biofertilizers and organic ameliorants has not been able to reduce the dose of NPK fertilizer on Inceptisols from Pasir Banteng.

Mapping Risks Associated with Soil Copper Contamination Using Availability and Bio-Availability Proxies at the European Scale

Soil contamination by trace elements like copper (Cu) can affect soil functioning. Environmental policies with guidelines and soil survey measurements still refer to the total contents of Cu in soils. However, Cu contents in soil solution or free Cu contents have been shown to be better proxies of risks of Cu mobility or (bio)availability for soil organisms. Several empirical equations have been defined at the local scale to predict the amounts of Cu in soil solution based on both total soil Cu contents and main soil parameters involved in the soil/solution partitioning. Nevertheless, despite the relevance for risk assessment, these equations are not applied at a large spatial scale due to difficulties to perform changes from local to regional. To progress in this challenge, we collected several empirical equations from literature and selected those allowing estimation of the amount of Cu in solution, used as a proxy of available Cu, from the knowledge of both total soil Cu contents and soil parameters. We did the same for the estimation of free Cu in solution, used as a proxy of bioavailable Cu These equations were used to provide European maps of (bio-)available Cu based on the one of total soil Cu over Europe. Results allowed comparing the maps of available and bio-available Cu at the European scale. This was done with respective median values of each form of Cu to identify specific areas of risks linked to these two proxies. Higher discrepancies were highlighted between the map of bioavailable Cu and the map of soil total Cu compared to the Cu available map. Such results can be used to assess environmental-related issues for land use planning.

Response of Annual Herbaceous Plant Leaching and Decomposition to Periodic Submergence in Mega-Reservoirs: Changes in Litter Nutrients and Soil Properties for Restoration

Litter decomposition is an important soil nutrient source that promotes vegetation in deteriorated riparian zones worldwide. The periodic submergence and sediment burial effects on two prominent annual herbaceous plants (Echinochloa crusgali and Bidens tripartite) are little known in mega-reservoir settings. Our study focuses on the mass and carbon loss and nutrient release from E. crusgali and B. tripartitle litter and changes in soil properties, which are important for riparian zone rehabilitation in the Three Gorges Dam Reservoir, China. This study adopted the litter bag method to explore the nutrient change characteristics and changes in soil properties at different sediment burial depths under flooding scenarios. Three burial depths (0 cm, 5 cm, and 10 cm) were used for these two plants, and the experiment lasted for 180 days. The results revealed that the litter decay rate was high at first in the incubation experiment, and the nutrient loss rate followed the pattern of K > P > N > C. The relationship between % C remaining and % mass remaining was nearly 1:1, and the total amount of P exhibited a leaching–enrichment–release state in the decomposition process. Nutrients were changed significantly in the soil and overlying water at the first decomposition stage. Still, the total soil nutrient change was insignificant at the end, except for the 10 cm burial of B. tripartitle. Moreover, oxidation–reduction potential was the main factor in the litter decomposition process at different burial depths. This study indicated that sediment deposition reduced litter mass loss, slowed down the release of N and P, and retained more C, but promoted the release of K. Conclusively, in litter decomposition under waterlogging, the total soil nutrient content changed little. However, litter does more to the soil than that. Therefore, it is necessary to study the residual soil litter’s continuous output after the water level declines for restoration purposes.

Soil fertility status in tidal land of Tirtomarto reservoir, Central Java, Indonesia

Reservoir tidal land used for agriculture is generally done when the reservoir water level begins to shrink. This land is used as a moor in dryland or lowland rice fields in the wetland. The purpose of the study was to determine the soil fertility status of the tidal land of the Tirtomarto reservoir, Central Java. Parameters tested include cation exchange capacity (CEC); base saturation (BS); C-Organic; total soil P and K levels according to the technical instructions for evaluating soil fertility. Soil samples were taken from three location points by the purposive sampling method. The results showed that most of the soil samples contained low to very low nutrients, except for the total P content which had a high value. Therefore, the fertility status in the tidal land of the Tirtomarto reservoir, Central Java, can be categorized as low. The low fertility status of the soil at the study site was due to the limiting factors, namely the low C-organic content of the soil, low K total soil, and low cation exchange capacity and base saturation.

Stability of Woodchips Biochar and Impact on Soil Carbon Stocks: Results from a Two-Year Field Experiment

Biochar has been shown to improve soil quality and crop yields. Furthermore, thanks to its high carbon content (C) and stable chemical structure, biochar can sequester C in the soil for a long time, mitigating climate change. However, the variability in published biochar stability in the soil makes verifying this trait under different environmental and agricultural conditions necessary. Moreover, most of the published literature refers to short-term incubation experiments, which are considered to not adequately represent long-term dynamics under field conditions. This article reports the results of a field experiment carried out in a vineyard near Merano, northern Italy, where the stability of woodchips biochar in soil, its impact on the total soil C stocks as well as on the original soil organic C (priming effect) were studied over two years. Vineyard soil (Dystric Eutrochrept) was amended with biochar (25 and 50 t ha−1) alone or together with compost (45 t ha−1) and compared with unamended control soil. Two methods assessed the stability of biochar in soil: the isotopic mass balance approach and the quantification of Benzene PolyCarboxylic Acids (BPCAs), molecular markers of biochar. The amount of C in the soil organic matter (SOM-C) was determined in the amended plots by subtracting the amount of biochar-C from the total soil organic C stock, and the occurrence of priming effect was verified by comparing SOM-C values at the beginning and at the end of the experiment. Results did not show any significant biochar degradation for both application rates, but results were characterized by a high variation. The application of 50 t ha−1 of biochar significantly increased soil C stock while no effect of biochar on the degradation of SOM-C was observed. Results were confirmed in the case of biochar application together with compost. It can be concluded that the use of woodchips biochar as a soil amendment can increase soil C content in the medium term. However, further analyses are recommended to evaluate the impact of biochar on climate change mitigation in the long term.

Perbaikan Sifat Fisik Tanah Inceptisol dan Pertumbuhan Tanaman Jagung (Zea mays L.) akibat Pemberian Kompos Granul Ela Sagu dan Pupuk Fosfat

Percobaan pot di rumah kaca dirancang untuk mengetahui pengaruh kompos granular limbah empulur sagu dan pupuk fosfat terhadap peningkatan karakteristik fisik Inceptisols dan pertumbuhan jagung. Percobaan menggunakan Rancangan Acak Lengkap faktorial 3 x 3 dengan 3 ulangan. Faktor pertama adalah KGES 0 (tanpa kompos granul ampas sagu), KGES 1 (100 g.pot-1), dan KGES 2 (200 g.pot-1) berupa kompos granul limbah empulur sagu; faktor kedua adalah pupuk P0 (tanpa fosfat), P1 (0,326 g.pot-1) dan P2 (0,652 g.pot-1). Hasil percobaan menunjukkan bahwa pemberian kompos granular limbah empulur sagu dan pupuk fosfor berpengaruh nyata terhadap soil bulk density, particle density, soil porosity, fast drainage pores, slow drainage pores, available water pores, unavailable water pores, total soil-P, dan tinggi tanaman. Sedangkan pupuk fosfor tidak berpengaruh nyata terhadap soil bulk density, porosity, slow drainage pores, unavailable water pores, dan tinggi tanaman.