•Total oxalate extractable iron(III)oxide pool reduced within 21 days of incubation.•Aluminium- and non-reduced iron(III)oxides recaptures mobilized phosphorus (P).•Langmuir sorption equilibrium ...between residual sorption capacity and P in solution.•Reciprocal relationship between residual sorption capacity and phosphorus release.
Rewetting of drained agricultural lowland peat soils is followed by the risk of increased phosphorus (P) release to downstream systems, thereby challenging their restoration as nutrient sinks for years to decades. While extensive knowledge is available on P mobilization under anaerobic conditions caused by reductive (Fe(III))-oxide dissolution, the net P release to the aqueous phase (PSol) is only poorly understood due to unknown significance of P re-sorption to aluminum (Al) oxides and non-reduced Fe(III)-oxides. We therefore hypothesize that PSol is a function of the sorption capacity and P saturation of Al-oxides and non-reduced Fe(III)-oxides. A comprehensive set of 47 Danish topsoil and subsoil samples from agricultural lowlands were incubated for up to 148 days in the laboratory under anoxic and water-saturated conditions at room temperature. Oxalate-extractable Fe, Al and P (Feox, Alox and Pox) varied by three orders of magnitude, with Feox ranging between 1.8 and 1590 mmol kg−1; Alox and Pox also showed high variation with maximum contents of 883 and 153 mmol kg−1, respectively. Bicarbonate-dithionite generally extracted 2 times less Fe, Al and P (FeBD, AlBD, PBD) than oxalate. Oxalate extraction data were used to calculate the degree of P saturation (DPS) and P sorption capacity (PSC). The extent of Fe(III)-oxide reduction measured as 0.1 M HCl extractable Fe(II)HCl was well described by first-order kinetics with rate constants ranging between 0.01 and 0.3 d-1.
The estimated maximum Fe(II)HCl produced (Fe(II)max) ranged between 3 and 1490 mmol Fe(II) kg−1, with Feox corresponding to Fe(II)max values very closely. For most soils almost full dissolution of the entire Feox pool was achieved within 21 days of incubation. PSol concentrations, measured in the soil solution extract, ranged between 0.05 and 5.05 mg L-1, increasing with incubation time for most of the soils. While PSol was not correlated with FeBD:PBD and Feox:Pox, DPS, total P (PT) or total Fe (FeT):PT ratio, the investigations revealed a strong reciprocal relationship between the residual sorption capacity (RSC) of the soils, i.e., PSC subtracted the Fe(III)-oxides reduced, and the PSol/Pox ratio. Moreover, the results showed low or lack of P release to the aqueous phase, even for the soil samples where all Feox pools were reduced, if the RSC of the soil was above 100 mmol kg−1. This highlights the importance of redox-stable Al-oxides to capture mobilized P from rewetted lowland peat soils.
Nitrous oxide (N2O) is a potent greenhouse gas (GHG) whose emission from soil can be enhanced by ruminant excretal returns in grasslands. The default (Tier 1) emission factors (EF3PRP; i.e. ...proportion of deposited nitrogen emitted as N2O) for ruminant excreta deposition are associated with a wide range of uncertainties and the development of country-specific (Tier 2) EF3PRP is encouraged. In Ireland, a Tier 2 EF3PRP has been developed for cattle excreta but no data are available for sheep. The aim of this study was to generate data to contribute to the derivation of a Tier 2 EF3PRP for sheep excreta, while assessing the effect of excreta type, grassland type and season of deposition on N2O emissions. An experiment was carried out on two sites in the west of Ireland: a managed lowland grassland (LOW) and an extensively grazed hill pasture (HILL), characterised by mineral and acid peat soils, respectively. For each season, four treatments were applied to the soil in a fully randomized block design: control (C), sheep urine (U), sheep dung (D), and artificial urine (AU). Nitrous oxide fluxes were assessed over a full year following each application of treatments, using a static chambers methodology. Results showed a brief initial peak following each application of U/AU in LOW but not in HILL. Cumulative N2O emissions were significantly higher from the lowland site. Average EF3PRP for combined excreta was negligible on both sites, thus lower than the IPCC Tier 1 EF3PRP. Causes of low emissions are likely to depend on site characteristics (e.g. soil acidity in HILL) and season of application (i.e. ammonia volatilisation in summer). This study showed very low N2O emissions from sheep excretal returns in Irish grasslands and highlighted the importance of developing Tier 2, animal-specific EF3PRP. More experimental grasslands should be assessed to confirm these results.
Display omitted
•Low N2O emissions measured from sheep excreta applied to two temperate grasslands.•Lower emissions on acidic peat soil than on mineral soil•Emissions from urine not higher than from dung.•Emissions factors lower than IPCC default value at average of 0.3 %•Causes of low emissions vary with site and season of deposition.
•GHG fluxes were measured from an undrained and four drained sites in a temperate bog.•Fluxes were measured at 1–2 week intervals using static chambers.•Soil respiration at undrained bog ...(1.8 Mg CO2-C ha−1 yr−1) was lower than at the drained sites (5.0–8.8 Mg CO2-C ha−1).•N2O emission as high as 37.7 kg N2O ha−1 yr−1 was measured from a cropland.•CH4 emission was high at undrained bog (172 kg CH4 ha−1 yr−1), but negligible at the drained sites (−1.5 to 1.5 kg CH4 ha−1 yr−1).
Peatlands drained for agriculture are sources of atmospheric carbon dioxide (CO2) and nitrous oxide (N2O). Resulting emissions may depend on land-use, often as grassland or cropland, but few studies have directly compared the effects of land-uses. Here, we measured annual emissions of CO2, N2O and methane (CH4) from five sites in a temperate bog, representing an undrained natural bog (NB) site, and four drained sites used as permanent grassland (PG) and croplands with rotations of oat-potato, oat-spring barley and potato-spring barley (PO:SB) in the study year. Gas fluxes were measured at 1–2 week intervals using static chambers, and auxiliary data were obtained, such as temperature, depth of water table, ratio-vegetation index, pH and soil mineral N. Annual CO2 emissions were derived from empirical modelling, whereas CH4 and N2O emissions were linearly interpolated between measurement dates by bootstrapping. Soil respiration was lower at the NB site (1.8 Mg CO2-C ha−1 yr−1) than at the drained sites where emissions were in the range of 5.0–8.8 Mg CO2-C ha−1 yr−1. The N2O emission was negligible at NB (0.3 kg N2O ha−1 yr−1), low at three of the drained sites (1.5–3.7 kg N2O ha−1 yr–1), but high at PO:SB (37.7 kg N2O ha−1 yr−1). The CH4 emission was high at NB (172 kg CH4 ha−1 yr−1), but negligible at the drained sites (−1.5 to 1.5 kg CH4 ha−1 yr−1). The soil respiration at the drained sites indicated that peat losses were rather similar among the different cropping systems and depended mostly on drainage status, although soil respiration and peat mineralization may not scale directly. The pattern of N2O emissions suggested an increased risk of N2O emission from potato cultivation before and after the period of potato growth, likely due to microbial availability of NO3– outside the growing season. For initiatives aiming at reduction of greenhouse gas emissions from agricultural peat soils, this means that, e.g., conversion from cropland to permanent grassland should preferably be accompanied by measures of rewetting, whereas for potato cropping, N availability outside the growing season should be minimized.
Moringa oleifera (Lam.) has become highly valued. Vegetative propagation methods can address the limitations and make the cultivation process simpler. Our research aimed to determine the best ...conditions for early growth and chlorophyll content of Moringa oleifera cutting stems through the use of different planting media and hormone applications. A 3x3 factorial pot experiment design was used, with three types of growing media (100% peat soil (PS), 50% peat soil (PS) + 50% mushroom baglog waste (MBW), and 50% peat soil (PS) + 50% husk charcoal (HC) and three hormone treatments (coconut water, atonik (3 ml L-1 water), and 100 ppm rootone-F) being tested. The experiment was carried out in a completely randomized design with 3 replications. Results showed that the use of a 50% peat soil (PS) + 50% husk charcoal (HC) and the application of rootone-F significantly had a significant impact on the chlorophyll content. Neither the use of 50% peat soil (PS) + 50% husk charcoal (HC) nor the application of rootone-F, singly, was favorable for promoting bud length, root volume, and chlorophyll content. It is recommended to use 50% peat soil (PS) + 50% husk charcoal (HC) media and rootone-F for successful vegetative propagation and subsequent domestication.
Abstract
This review present various ways to improve peat soil stability or strength. There is need to investigate the applicability of cationic grouts in addition to biochar in peat enhancement ...towards the development of wetland soil for construction purposes. The effects of several cationic stabilizers such as monovalent, divalent (calcium oxide and calcium chloride), and trivalent in addition to biochar would require investigation on the shear strength improvement of the Sibu peat samples. The unconfined compressive strength (UCS) tests would need to be performed after 7, 21, and 30 days of curing, respectively. Apart from the physicochemical characteristics of the stabilized peat, scanning electron microscopy and energy-dispersive X-ray spectroscopy tests would also be necessary to study the changes in the microstructure. Some studies have shown improvement in the application of stabilizers in peat soil towards development of wetlands. These are highlighted in this article. Where changes are observed due to improvement via the various cationic stabilizers and biochar addition, an explanation considering the mineralogical and physicochemical composition on the peat would be important.
Today, many wetlands have been converted into agricultural, industrial, and residential areas. This conversion of land functions creates new problems for the environment and human, one of which is ...land fires. The results of land fires can also cause other problems that results in losses in various fields, such as human health, the economy, and other fields. The emergence of smog as a result of land fires can cause respiratory problems, disruption of the transportation system, conflicts between neighboring countries, and the others. South Sumatra Province is one of the largest contributors to the haze as a result of land fires, especially its wetlands. Ogan Ilir Regency is one of the areas in South Sumatra Province which has extensive wetlands and fires frequently occur. Fires are caused by triggering factors, one of which is natural factors such as a prolonged dry season, availability of water supply, and intensity of rainfall. This study is an analytic descriptive study that aimed to provide an overview of environmental conditions on land, the majority of which are wetlands which experienced fires in Ogan Ilir Regency in 2019. The environmental conditions studied included soil and vegetation types. The data obtained will be displayed through tables and graphs, then interpreted and analyzed descriptively. The type of data used is secondary data in the form of a report by the Regional Disaster Management Agency Ogan Ilir Regency related to land fires in OI Regency and processed using the Geographic Information System (GIS) application. The results of the analysis show that the area of land fires that mostly occurred in North Indralaya District was 382,7 hectares with a total of 144 hotspots. The burnt area was dominated by peat soil (53%) and scrub vegetation (43%).
The lowland peatlands of south-east Asia represent an immense reservoir of fossil carbon and are reportedly responsible for 30% of the global carbon dioxide (CO₂) emissions from Land Use, Land Use ...Change and Forestry. This paper provides a review and meta-analysis of available literature on greenhouse gas fluxes from tropical peat soils in south-east Asia. As in other parts of the world, water level is the main control on greenhouse gas fluxes from south-east Asian peat soils. Based on subsidence data we calculate emissions of at least 900 g CO₂ m⁻² a⁻¹ (~250 g C m⁻² a⁻¹) for each 10 cm of additional drainage depth. This is a conservative estimate as the role of oxidation in subsidence and the increased bulk density of the uppermost drained peat layers are yet insufficiently quantified. The majority of published CO₂ flux measurements from south-east Asian peat soils concerns undifferentiated respiration at floor level, providing inadequate insight on the peat carbon balance. In contrast to previous assumptions, regular peat oxidation after drainage might contribute more to the regional long-term annual CO₂ emissions than peat fires. Methane fluxes are negligible at low water levels and amount to up to 3 mg CH₄ m⁻² h⁻¹ at high water levels, which is low compared with emissions from boreal and temperate peatlands. The latter emissions may be exceeded by fluxes from rice paddies on tropical peat soil, however. N₂O fluxes are erratic with extremely high values upon application of fertilizer to wet peat soils. Current data on CO₂ and CH₄ fluxes indicate that peatland rewetting in south-east Asia will lead to substantial reductions of net greenhouse gas emissions. There is, however, an urgent need for further quantitative research on carbon exchange to support the development of consistent policies for climate change mitigation.
Drought induced by climate warming and human activities regulates carbon (C) cycling of peatlands by changing plant community composition and soil properties. Estimating the responses of peatlands C ...cycling to environmental changes requires further study of C: nitrogen (N): phosphorus (P) stoichiometric ratios of soil, plants, and enzyme activities. However, systematic studies on the stoichiometry of above-ground and below-ground ecosystems of peatlands post drainage remain scarce. This study compared stoichimetric ratios of plant and soil and stoichimetric ratios of enzyme activities with different functions in two different parts of a minerotrophic peatland, a natural undisturbed part and a part that had been drained for almost 50 years, in Northern China. For the shrub plants, the average C:N:P ratios of leaf in natural and drained peatland were 448:17:1 and 393:15:1, respectively. This indicated that the growth rate of shrub plants is higher in the drained peatland than in the natural peatland, which makes P element more concentrated in the photosynthetic site. However, from the perspective of the dominant plant, the mean C:N:P ratio of Carex leaf was 650:25:1 in the natural peatland, but was 1028:50:1 for Dasiphora fruticosa in drained peatland. This indicated that the intensification of P-limitation of plant growth after drainage. Soil C:N:P ratios of above water table depth (AWT) were 238:15:1 and 277:12:1, but were 383:17:1 and 404:19:1 for below water table depth (BWT) in the natural and the drained peatland, respectively. Soil C:P ratios were greater than the threshold elemental ratio of C:P (174:1), but the soil C:N ratios were less than the threshold elemental ratio of C:N (23:1), which suggested that P was the most limiting nutrient of soil. The soil microbial activities were co-limited by C&P in Baijianghe peatlands. However, the microbial metabolic P limitation was intensified, but the C limitation was weakened for the above water table depth soil after long-term drainage. There are connection between plant-microbe P limitation in peatlands. The P limitation of microbial metabolism was significant positively correlated with soil C:N but negatively with soil moisture. The increase in the lignocelluloses index suggested considerable decomposition of soil organic matter after peatland drainage. These results of stoichiometric ratios from above- to below ground could provide scientific base for the C cycling of peatland undergone climate change.
Display omitted
•The C:P and N:P decreased in leaf, but increased in stems and roots after drainage.•Soil C:N and C:P ratios of AWT depth increased, but N:P ratio decreased after drainage.•The vector length of AWT depth decreased, but the vector angle increased after drainage.•The P-limitations of plant growth and microbial metabolism were intensified after drainage.•The nutrient limitations of microbial metabolism were regulated by soil moisture and C:N ratio.
PDF
