Higher Amounts Of Soil Organic Carbon Research Articles

Influence of Organic Amendments on Soil Carbon Sequestration Potential of Paddy Soils under Two Irrigation Regimes

Soil organic carbon (OC) is one of the most important soil components regulating soil quality, fertility and agronomic productivity as well as the global carbon (C) cycle. Soil acts as a sink for global C, which can be influenced by the water regime and organic matter (OM) management in field. The aim of this study is to evaluate the effect of the application of different organic amendments on C sequestration in paddy soils under contrasting irrigation regimes. A 4-month pot experiment was conducted under net house conditions and the treatments were composed of two organic amendments: rice straw (RS) and poultry manure (PM); four application rates of amendment: 0 g (control), 2.5 g, 5.0 g and 15.0 g kg−1 soil; and two irrigation regimes: (i) continuous waterlogging condition (CWL) and (ii) alternate wetting and drying (AWD). After the incubation period, soil samples were collected from the pot and isolated into labile (>53 µm) and mineral-associated (<53 µm) OM. Bulk (before and after incubation) and fractionated soil samples were analyzed for OC, total nitrogen (N), C:N ratio; and C sequestration percentage was calculated. Relatively higher amounts of soil OC were present in CWL condition (1.23%) than AWD (1.13%). The C sequestration potential also showed the similar trend (CWL: 47% > AWD: 35%). This was explained by the induced aerobic condition in between the anerobic condition in AWD and the continuous anaerobic condition in CWL which resulted in a difference in OM decomposition. The mineral-associated OM fraction (<53 µm) was higher in the CWL condition than AWD condition which also indicated the importance of the chemical stabilization of OC (OC bound to minerals) in the CWL condition. The application of PM led to a significant increase (45%) in C sequestration potential than RS (37%). This could be attributed to C:N ratio and probable biochemical composition of amendments which resulted in lower decomposability of PM than RS, and also in line with the higher distribution of OC in mineral-bound OM than labile fraction. The application of higher organic amendments did not increase OC content, and declined C sequestration potential in soils as the microbial activity presumably did not match with the amendment amount. Overall, C sequestration potential was higher with 5 g PM kg−1 soil application under CWL-irrigated paddy soil. The findings indicated the need to pay more attention to the selection of the proper type and rate of organic amendments for higher C sequestration in soil under a specific irrigation system for sustainable agriculture.

Towards complete and harmonized assessment of soil carbon stocks and balance in forests: The ability of the Yasso07 model across a wide gradient of climatic and forest conditions in Europe

Accurate carbon-balance accounting in forest soils is necessary for the development of climate change policy. However, changes in soil organic carbon (SOC) occur slowly and these changes may not be captured through repeated soil inventories. Simulation models may be used as alternatives to SOC measurement. The Yasso07 model presents a suitable alternative because most of the data required for the application are readily available in countries with common forest surveys. In this study, we test the suitability of Yasso07 for simulating SOC stocks and stock changes in a variety of European forests affected by different climatic, land use and forest management conditions and we address country-specific cases with differing resources and data availability. The simulated SOC stocks differed only slightly from measured data, providing realistic, reasonable mean SOC estimations per region or forest type. The change in the soil carbon pool over time, which is the target parameter for SOC reporting, was generally found to be plausible although not in the case of Mediterranean forest soils. As expected under stable forest management conditions, both land cover and climate play major roles in determining the SOC stock in forest soils. Greater mean SOC stocks were observed in northern latitudes (or at higher altitude) than in southern latitudes (or plains) and conifer forests were found to store a notably higher amount of SOC than broadleaf forests. Furthermore, as regards change in SOC, an inter-annual sink effect was identified for most of the European forest types studied. Our findings corroborate the suitability of Yasso07 to assess the impact of forest management and land use change on the SOC balance of forests soils, as well as to accurately simulate SOC in dead organic matter (DOM) and mineral soil pools separately. The obstacles encountered when applying the Yasso07 model reflect a lack of available input data. Future research should focus on improving our knowledge of C inputs from compartments such as shrubs, herbs, coarse woody debris and fine roots. This should include turnover rates and quality of the litter in all forest compartments from a wider variety of tree species and sites. Despite the limitations identified, the SOC balance estimations provided by the Yasso07 model are sufficiently complete, accurate and transparent to make it suitable for reporting purposes such as those required under the UNFCCC (United Nations Framework Convention on Climate Change) and KP (Kyoto Protocol) for a wide range of forest conditions in Europe.

Targeted management of organic resources for sustainably increasing soil organic carbon: Observations and perspectives for resource use and climate adaptations in northern Ghana

ABSTRACTSince soil organic matter (SOM) buffers against impacts of climatic variability, the objective of this study was to assess on-farm distribution of SOM and propose realistic options for increasing SOM and thus the adaptation of smallholder farmers to climate change and variability in the interior northern savannah of Ghana. Data and information on spatial distribution of soil organic carbon (SOC), current practices that could enhance climate adaptation including management of organic resources were collected through biophysical assessments and snap community surveys. Even though homestead fields were more frequently cultivated, higher amounts of SOC (15 ± 2 g kg−1) were observed in homesteads when compared to the periphery cropped sections in bushes (SOC = 9 ± 1 g kg−1). Possibly, a combination of household wastes, droppings of domestic animals that are mostly reared in a free-range system, manures applied to crops and cultural norms of chieftaincy, which cause short-term fallowing of homestead fields could account for the differences in SOC. Use of organic resources for soil amendment among farmers was low (31% of interviewed farmers) due largely to ignorance of fertilizer values of manures and residues, traditions for bush-burning and competing use of organic resources for fuels. Our findings suggest a need for effective management practices, training and awareness aimed at improving management of organic resources and, consequently, increasing SOC and resilience to climate-change-induced risks.

Can vegetation types work as an indicator of soil organic carbon? An insight from native vegetations in Nepal

Soil is the largest pool of carbon after the ocean. The assessment of soil organic carbon (SOC) stocks under different types of vegetations is critical for evidence-based implementation of soil carbon trading under different market mechanisms. Using data from 490 permanent soil sample plots with elevations ranging from 271m to 3238m above sea level, from three different watersheds in Nepal, this study aims to compare SOC under five different forest types and determine whether forest types could be indicator of SOC: Shorea robusta; mixed broadleaf; Schima-Castanopsis; pine; and Rhododendron-Quercus forests. In each vegetation type forests with dense canopies (≥70% canopy cover) have higher amounts of SOC than that of open canopy forests (<70% canopy cover). On average, with up to 30cm soil depth, dense canopy Rhododendron-Quercus forest has the highest amount of SOC (14,136gC/m2), followed by dense canopy mixed broadleaf forest (12,576gC/m2). One-way analysis of variance (ANOVA) indicates significant differences in soil organic carbon (SOC) amounts across the five forest types (df=485, F=17.299, p=0.000) and therefore forest types could be indicator of SOC. Moreover, within the similar altitudinal zone and topographic, edaphic and climatic environments: soils under the mixed species forests have higher amounts of SOC than that of single species dominated forests; and soils under forests with nitrogen fixing trees have a higher amount of SOC than those from other forests. Therefore, in addition to forest types these two conditions within the given vegetation types could work as sub-indicators of SOC. In comparison with global studies, all Nepalese forest types had much higher levels of SOC. Only two of the seven factors/indicators investigated (altitude and average age of dominant trees) were found to have significant impacts (r=0.33 to 0.64) on SOC and only in the dense and sparse canopy pine forests. The reasons of not having any impacts of all other factors on SOC in different vegetation types have been discussed.

Storage and Stability of Soil Organic Carbon in Aspen and Conifer Forest Soils of Northern Utah

This study compares the amount, distribution, and stability of soil organic carbon (SOC) in six paired quaking aspen (Populus tremuloides Michx) and conifer plots at three locations in northern Utah, to assess the influence of vegetation cover and other biotic and abiotic drivers on SOC storage capacity in seasonally dry environments. Aspen soils accumulated significantly more SOC in the mineral soil (0–60 cm) (92.2 ± 26.7 Mg C ha−1 vs. 66.9 ± 18.6 Mg C ha−1 under conifers), and despite thicker O horizons under conifers that contained higher amounts of SOC (11.6 ± 8.8 Mg C ha−1 under conifers vs. 1.65 ± 0.38 Mg C ha−1 in aspen), across all sites SOC storage was 25% higher under aspen. Shallow soil cores (0–15 cm) did not indicate significant differences in SOC with vegetation type. The SOC under aspen was also more stable, indicated by well‐developed mollic epipedon (A horizon 38–53‐cm thick vs. 5.5–34 cm under conifers), slower turnover of surficial SOC deduced from long‐term laboratory incubations (67.7 ± 15.7 g CO2–C per kg C for aspen vs. 130.9 ± 41.3 g CO2–C per kg C for conifer soils), and a greater preponderance of mineral‐associated SOC (55±13% in aspen vs. 41±13% in conifer). Aspen soils were generally wetter and we hypothesize that rapid litter turnover coupled with greater water supply may have caused greater downward redistribution and adsorption of dissolved organic carbon (DOC) in aspen soils.

Reservas de materia orgánica en suelos y distribución espacial en la cuenca del Río Grande de Arecibo

Se estudió la influencia de los factores orden de suelo, fase y uso de terreno sobre la distribución espacial del carbono orgánico (SOC) y nitrógeno total del suelo (SON) en la cuenca del Río Grande de Arecibo, Puerto Rico. Los objetivos eran cuantificar las reservas de C y N en suelos y el potencial de secuestro de C de la cuenca. Se tomaron muestras de suelos representativos de la cuenca de un área de 39,361 ha (o 87.3% de la totalidad del área de la cuenca) bajo bosque secundario, pastura y uso agrícola. Los suelos de la cuenca almacenan 5.02 x 10s Mg de SOC y 0.48 x 10s Mg de SON a una profundidad de 100 cm. Las medias ponderadas de SOC y SON a 15 cm de profundidad fueron 4.33 kg C/m2 y 0.390 kg N/m2, respectivamente, y a una profundidad de 100 cm fueron de 11.13 kg C/m2 y 1.08 kg N/m2, respectivamente. La interacción entre unidad de mapa y uso de terreno representó el mejor estimado de SOC por la mayor resolución espacial. Suelos bajo bosque secundario y pasturas tuvieron mayor SOC (12.8 y 9.79 kg C/m2, respectivamente)(P &lt; 0.05) que suelos bajo uso agrícola (7.90 kg C/m2) a una profundidad de 100 cm. El SOC a una profundidad de 15 cm fue similar entre Oxisoles y Ultisoles, los que juntos fueron mayores que los Inceptisoles con valores de 5.85, 4.77, y 3.18 kg C/m2, respectivamente. Estimamos que la cuenca puede secuestrar 46,627 Mg C adicionales, lo cual representa un aumento de 1.0% sobre el nivel actual de C.