Tillage effect on organic carbon in a purple paddy soil

The distribution and storage of soil organic carbon （SOC） based on a long-term experiment with various tillage systems were studied in a paddy soil derived from purple soil in Chongqing, China. Organic carbon storage in the 0-20 and 0-40 cm soil layers under different tillage systems were in an order： ridge tillage with rice-rape rotation （RT-rr） 〉 conventional tillage with rice only （CT-r） 〉 ridge tillage with rice only （RT-r） 〉 conventional tillage with rice-rape rotation （CT-rr）. The RT-rr system had significantly higher levels of soil organic carbon in the 0-40 cm topsoil, while the proportion of the total remaining organic carbon in the total soil organic carbon in the 0-10 cm layer was greatest in the RT-rr system. This was the reason why the RT-rr system enhanced soil organic carbon storage. These showed that tillage system type was crucial for carbon storage. Carbon levels in soil humus and crop-yield results showed that the RT-rr system enhanced soil fertility and crop productivity. Adoption of this tillage system would be beneficial both for environmental protection and economic development.     

Loss‐on‐ignition as an estimator of soil organic carbon in a‐horizon forestry soils

Abstract

The determination of soil organic matter by wet digestion techniques is a slow and laborious analysis. Loss‐on‐ignition (LOI) provides a simple alternative technique for the estimation of soil organic carbon in non‐calcareous A horizon soils of the Natal midlands and Zululand forestry regions. Using multiple regressional techniques, the relationships between loss‐on‐ignition, Walkley organic carbon and soil texture for 55 soils were determined over a range of ignition temperatures. The relationships hold best for soil samples with relatively low organic carbon contents (< 5%). The optimum temperature for ignition was found to occur at 450°C and resulted in the relationship: Soil organic carbon = 0.284*LOI percent. No advantage is gained through ignition at higher temperatures due to the loss of clay mineral structural water, even if the soil texture is accurately known.     

Use of loss‐on‐ignition to assess soil organic carbon in forest soils

Abstract

Forest floor and mineral soils were collected from 169 conifer and hardwood forested plots across Minnesota, Wisconsin, and Michigan. Regression equations were developed between LOI and organic C for 20% of the samples (n=337), and LOI was then used to predict organic C on all of the samples. Results indicated that LOI is a good estimator of organic C in these soils, but that separate equations were needed for different soil strata. Percent organic C in forest floors was greater in conifer stands compared to hardwood (means of 35.1 and 30.1%, respectively)     

Inorganic and organic ligands induced changes in Pb sorption of arid ‎clay and calcareous loamy sand soils

The objective of this study was to investigate sorption, desorption, and immobilization of Pb in the clay and calcareous loamy sand soils treated with inorganic ligands (NO₃^?, Cl^? and H₂PO₄^?). Pb sorption was also determined in the presence of oxalate and citrate. The maximum Pb sorption capacities (q) ranged from 42.2 to 47.1 mmol kg^?1 for the clay soil, and from 45.2 to 47.0 mmol kg^?1 for loamy sand soil. It was observed that the binding energy constant (k) for Pb sorbed onto loamy sand soil (528–1061) is higher than that for clay soil (24.38–55.29). The loamy sand soil-sorbed greater quantities of Pb compared to the clay soil when initial pH was ≥ 3. However, it had lower sorption capacity at the lowest initial pH of 2. Additionally, the greatest Pb sorption and immobilization occurred in the soil treated with H₂PO₄. In the clay soil, the sorption of Pb was depressed at 0.1 mol kg^?1 of Cl^?, as compared with other ligands. Concerning organic acids, citrate ligand showed the highest decrease in Pb sorption. It could be concluded that the nature of Pb sorption can depend on the type and quantity of ligands present, as well as the soil type.     

Biological carbon assimilation and dynamics in a flooded rice – Soil system

Information on the input, distribution and fate of photosynthesized carbon (C) in plant–soil systems is essential for understanding their nutrient and C dynamics. Our objectives were to: 1) quantify the input to, and distribution of, photosynthesized C by rice into selected soil C pools by using a C¹⁴ continuous labelling technique and 2) determine the influence of the photosynthesized C input on the decomposition of native soil organic carbon (SOC) under laboratory conditions. The amounts of C¹⁴ in soil organic C (SOC¹⁴) were soil dependent, and ranged from 114.3 to 348.2 mg C kg⁻¹, accounting for 0.73%–1.99% of total SOC after continuous labelling for 80 days. However, the mean SOC¹⁴ concentrations in unplanted soils (31.9–64.6 mg kg⁻¹) were accounted for 21.5% of the rice-planted soils. The amounts of C¹⁴ in the dissolved organic C (DOC¹⁴) and in the microbial biomass C (MBC¹⁴), as percentages of SOC¹⁴, were 2.21%–3.54% and 9.72%–17.97%, respectively. The DOC¹⁴ and MBC¹⁴ were 6.72%–14.64% and 1.70%–7.67% of total DOC and MBC respectively after 80-d of rice growth. At 80-d of labelling, the SOC¹⁴ concentration was positively correlated with the MBC¹⁴ concentration and rice root biomass. Rice growth promotes more photosynthesized (newly-derived) C into soil C pools compared to unplanted soils, reflecting the release of root exudates from rice roots. Laboratory incubation of photosynthesized (plant-derived) C in soil decreased the decomposition of native SOC (i.e. a negative priming effect), in some, but not all cases. If this negative priming effect of the new C on native SOC also occurs in the field in the longer term, paddy soils will probably sequester more C from the atmosphere if more photosynthesized C enters them.     

The impact of a bio-fertilizer on the soil organic matter status and carbon sequestration—results from a field-scale study

Purpose

The application of bio-fertilizers is one of the management practices that can help to maintain or increase the content of organic matter (OM) and improve soil fertility in arable soils. While some results have been obtained in relation to the influence of bio-fertilizers on organic matter content, less in known about the fractional composition of humus.

Materials and methods

The aim of this study was to determine the effects of the bio-fertilizer UGmax on soil total organic carbon (TOC), dissolved organic carbon (DOC), and the fractional composition of organic matter (C of humic acids (CHAs), C of fulvic acids (CFAs), and C in humins) in the humus horizon of an arable field. Measurements were taken in 2005 before the application of UGmax and in 2008, 3 years after its application, which was done in 2005, 2006, and 2007. Forty soil samples were taken in 2005 (the control year without UGmax), while 20 samples were taken after UGmax treatment and 20 from the control in 2008. Samples were always collected after the plants were harvested.

Results and discussion

After the 3-year period of the experiment, the TOC content was 6.3 % higher in plots on which UGmax was applied in comparison to the control, while the DOC content was 0.19 percentage points lower after 3 years of bio-fertilizer use as compared to the initial year of the experiment. The contribution of DOC to TOC decreased significantly after the application of UGmax in comparison with the control. The content of CFAs and its contribution in the TOC pools in soil without UGmax was higher at the end of the experiment compared to the beginning, while there was an inverse relationship in the soil with the bio-fertilizer. In comparison with the control, organic matter in the soil treated with UGmax had a higher content of C of humic acids, C in humins, and higher CHAs/CFAs ratio.

Conclusions

We conclude that the use of a bio-fertilizer that increases the stable fractions of organic matter provides evidence of an increase in the soil OM stability. In turn, the contribution of the organic matter fractions that are more resistant to decomposition is crucial for increasing soil carbon sequestration.

     

Assessment and prediction of changes in the reserves of organic carbon in abandoned soils of European Russia in 1990–2020

Experimental studies and the analysis of published data have shown that carbon reserves in soils generally increase upon soil exclusion from agricultural use. The rate of carbon accumulation in the abandoned soils depends on the soil type, the time elapsed since the soil abandoning (the restoration period), and the thickness of the layer for which the rate of carbon accumulation is determined. For the upper 20-cm-thick layer, it varies from 66 to 175 g C/m² per year in dependence on the type of soil and averages 111 g C/m² per year. The highest rate is typical of the first 10–15 years of soil restoration. According to our calculations, the carbon sequestration in the upper 20-cm-thick layer of Russian soils due to changes in land use was 184–673 Mt C in 1990–2005 and may reach 282–1030 Mt C by 2020.     

Input and migration of dissolved organic carbon in soils of forest ecosystems in the subzone of deciduous–coniferous forests

The results of four-year monitoring of natural waters in forest ecosystems of the Zvenigorod Biological Station (Moscow State University, Moscow oblast) show regular changes in the concentrations and fluxes of dissolved organic carbon (DOC) within the atmospheric precipitation–throughfall–soil waters system. Precipitation passing through the tree canopy is enriched with DOC (2–3 and 9–24 mg/L). The average carbon concentration in soil waters reaches 100–110 mg/L in complex spruce and pine–spruce forests and does not exceed 40–60 mg/L in spruce–birch forests.     

Nutrient management on crop productivity and changes in soil organic carbon and fertility in a four–year-old maize-wheat cropping system in Indo-Gangetic plains of India

The aim of this investigation was to prepare and evaluate organic manures (vermicompost, compost and FYM) and mineral fertilizers on crop productivity and changes in soil organic carbon (SOC) and fertility under a four-year-old maize-wheat cropping system. The results demonstrated that yields and nutrient uptake by crops increased significantly in plots receiving manures and mineral fertilizers either alone or in combination than unfertilized control. Application of manures and fertilizers also enhanced SOC, mineral N, Olsen-P and ammonium acetate-extractable K (NH₄OAc-K) after both the crops. Surface soil maintained greater build-up in SOC, mineral N, Olsen-P and NH₄OAc-K than sub-surface soil. Plots amended with manures at 5 t ha^?1 and 50% recommended dose of fertilizer (RDF) had pronounced impact on improving SOC and fertility after both the crops indicating that integrated use of manures and mineral fertilizers could be followed to improve and maintain soil fertility, increase crop productivity under intensive cropping system.     

Effects of NH4+ and NO3− on litter and soil organic carbon decomposition in a Chinese fir plantation forest in South China

Soil organic carbon (SOC) dynamics and nutrient availability determine the soil quality and fertility in a Chinese fir plantation forest in subtropical China. Uniformly ¹³C-labeled Chinese fir (Cunninghamia lanceolata) and alder (Alnus cremastogyne) leaf litter with or without 100 mg NH₄⁺ or NO₃⁻ were added to the soil. The purpose was to investigate the influence of N availability on the decomposition of the litter and native SOC. The production of CO₂, the natural abundance of ¹³C–CO₂, and the inorganic N dynamics were monitored. The results showed that Chinese fir (with a high C:N ratio) and alder (with a low C:N ratio) leaf litter caused significant positive priming effects (PEs) of 24% and 42%, respectively, at the end of the experiment (235 d). The PE dynamics showed that positive PE can last for at least 87 d. However, the possible occurrence of a significant negative PE with a sufficient incubation period is difficult to confirm. The application of both NH₄⁺ and NO₃⁻ was found to have a stimulating effect on the decomposition of Chinese fir and alder leaf litter in the early stage (0–15 d) of incubation, but an adverse effect in the late stage. Compared with NO₃⁻, NH₄⁺ caused a greater decrease in the PE induced by both Chinese fir and alder leaf litter. The effects of NH₄⁺ and NO₃⁻ on the PE dynamics had different patterns for different incubation stages. This result may indicate that the stability or recalcitrance of SOC, especially in such plantation forest soils, strongly depends on available leaf litter and application of N to the soil.     

Soil organic carbon pools and productivity in relation to nutrient management in a 20-year-old rice–berseem agroecosystem

Labile fractions of soil organic C (SOC) can respond rapidly to changes in C supply and are considered to be important indicators of soil quality. An attempt is made in this paper to investigate into the dynamics of total organic C (C _tot), oxidisable organic C (C _oc), very labile C (C _{frac 1}), labile C (C _{frac 2}), less labile C (C _{frac 3}), non-labile C (C _{frac 4}), microbial biomass C (C _mic), mineralizable C (C _min) and particulate organic C (C _p) in relation to the system productivity of a 20-year-old rice (Oryza sativa L)–berseem (Trifolium alexandrium L) cropping system with different management strategies [no fertilization, only NPK and NPK + FYM (farmyard manure) applied in different seasons] in the hot humid, subtropics of India. Cultivation over the years caused a net decrease, while balanced fertilization with NPK maintained the SOC. About 62% of the C applied as FYM was stabilized into SOC. The passive pool (C _{frac 3} + C _{frac 4}) constituted about 55% of the C _tot. A larger proportion (63%) of applied C was stabilized in the passive pool of SOC. Of the analysed pools, C _{frac 1}, C _mic, C _p and C _min were influenced most by the treatments imposed and explained higher per cent variability in the yield of the crops.     

Influence of air drying and soil gas‐phase carbon dioxide on DTPA‐extractable iron in calcareous soils

Abstract

The extraction of a field‐moist soil with DTPA will result in a level of extractable iron (Fe) lower than that of the air‐dried soil. Soil gas‐phase carbon dioxide (CO₂) levels may be considerably higher than ambient atmospheric levels, especially in wet soils in the field. This study was undertaken to determine whether gas‐phase CO₂ level influences the quantity of Fe extracted by DTPA. Three moist calcareous soils were incubated for 21 days, each at three different partial pressures of CO₂, after which the moist soils were extracted with DTPA. A sample of each soil was also air dried, and was subsequently extracted with DTPA. In each case, DTPA‐extractable Fe from the moist sample was lower than that from the air‐dried sample; however, DTPA‐extractable Fe increased with increasing CO₂ partial pressure of in the moist soils. DTPA‐extractable Fe concentration for a given soil following air drying was not significantly influenced by the CO₂ partial pressure during incubation of the originally field‐moist soil. DTPA‐extract pH of the moist soils followed the same trend as soil‐solution pH (i.e., as CO₂ concentration of the soil gas‐phase increased, soil solution pH and DTPA extract pH both decreased); however, the slope of the pH versus log P_CO2 curve was less pronounced in the DTPA extract due to the buffering capacity of the triethanolamine. From this study, it is concluded that elevated soil gas‐phase CO₂ partial pressure does not contribute to the lower level of DTPA‐extractable Fe observed when the extraction is performed on a field‐moist versus an air‐dried soil; increased CO₂ partial pressure actually resulted in a slight increase in concentration of DTPA‐extractable Fe obtained from a field‐moist soil.     

Effects of conservation tillage drills on soil quality indicators in a wheat–oilseed rape rotation: organic carbon,earthworms and water-stable aggregates

The effects of five conservation tillage drills with crop residue levels covering between 17% and 79% of the soil, and tillage depths ranging from 25 to 200 mm, were examined over 3 years. The tillage systems ranged from a relatively disruptive Farm System to a Low Disruption system, with three intermediate treatments labelled Sumo DTS, Claydon and Mzuri. The study involved field sites on a clay or clay loam soil, where winter wheat and oilseed rape were grown in rotation. In the clay field, the Mzuri and Low Disruption treatments, which produced the highest residue coverage, showed the greatest increase in surface total soil organic carbon (1.1 and 0.48 Mg C ha⁻¹, respectively) between years 1 and 3. The least disruptive tillage system also resulted in the highest density of earthworms (181–228 m⁻²), and the most disruptive system produced the lowest densities (75–98 m⁻²). In the third year, the least disruptive system also showed a higher proportion of water-stable aggregates (29.8%) than the other treatments (22.7%–25.3%). Linear regressions showed positive relationships of both soil organic carbon and earthworm density with surface residue cover, and of the proportion of water-stable aggregates with soil organic carbon.     

Determination of organic matter content in arid‐zone soils using a simple “loss‐on‐ignition” method

Abstract

A simple and rapid procedure for the determination of organic matter content in mineral soils by loss‐on‐ignition without pretreatment was studied. Attention was given to the possible effect of inorganic compounds abundant in mineral soils on the estimation of organic matter content by this method. Both fast heating (DTA‐TGA type) studies and prolonged heating procedures were employed on natural and “synthetic”; soils. The results were compared to those obtained by the dichromate wet‐oxidation method widely used in soil laboratories for organic matter determination. In a group of 91 soils collected from various mineral soils in Israel, and having OM contents between 0.09 and 13.23%, a correlation coefficient of 0.972 was obtained for the linear regression between organic matter content measured by the proposed method and organic carbon measured by the dichromate wet‐oxidation method.     

Measurement of Si adsorption and “Active Si” in a soil amended with slag fertilizers by using stable isotope 30SP

The silicic acid adsorption by a soil (Eutric Gleysols) where slag fertilizers were applied was measured by the addition of a silicic acid solution labelled with ³⁰Si after soil incubation, in order to study the effect of slag application on the specific Si adsorption by the soil and to estimate the amount of Si in the soil solid phase which can easily enter the soil solution. It was evident that the application of slags increased the ability of soil to adsorb Si. It was also shown that the ³⁰Si added was diluted with not only the Si present in the soil solution but also the Si dissolved from the soil solid phase. We proposed the use of the term “active” for Si in soil which can take part in the isotopic dilution within 1 h. The amount of active Si in the soil solid and liquid phases (D ₆₀ - value) was calculated from the ³⁰Si content in the soil solution and compared with the amount of Si taken up by rice plant (Oryza sativa L.), which was determined in our previous study. The buffering capacity of the soil for Si, which can reflect the ability of soil to maintain the Si concentration in the soil solution constant when Si is added to or removed from the soil, was also determined. The D ₆₀ - value and the Si buffering capacity of the soil increased by slag application. These increases were large when the alkalinity of the applied slags was high. The correlation study revealed that the D ₆₀ - value was a better index of Si availability of the soil than the amount of Si dissolved from the soil solid phase during the incubation when the slags were previously applied.     

Spatial variation of soil test phosphorus and potassium,oxalate‐extractable iron and aluminum,phosphorus‐retention index,and organic carbon content in soils of Western Australia

Abstract

Spatial variation of bicarbonate soil test phosphorus (P) and bicarbonate soil test potassium (K) was studied by measuring soil test values for 40 individual soil samples collected from random locations within eight uniform 100 m by 100 m field sites in south‐western Australia. In addition, for five of the sites, spatial variation of the three P sorption indices (ammonium oxalate extractable iron, ammonium oxalate extractable aluminum, and the P retention index) and of organic carbon (C) was measured for 20 individual soils samples. Spatial variation was found to be large, with coefficient of variation (CV) exceeding 20% in most cases, and 50% in some cases. It is therefore essential to collect an adequate number of soil samples from uniform areas in paddocks in order to provide a representative composite sample to measure the soil properties.     

Effect of conservation agriculture on soil organic and inorganic carbon sequestration and lability: A study from a rice–wheat cropping system on a calcareous soil of the eastern Indo-Gangetic Plains

Increasing soil carbon (C) in arable soils is an important strategy to achieve sustainable yields and mitigate climate change. We investigated changes in soil organic and inorganic carbon (SOC and SIC) under conservation agriculture (CA) in a calcareous soil of the eastern Indo-Gangetic Plains of India. The treatments were as follows: conventional-till rice and wheat (CT-CT), CT rice and zero-till wheat (CT-ZT), ZT direct seeded rice (DSR) and CT wheat (ZT-CT), ZTDSR and ZT wheat without crop residue retention (ZT-ZT), ZT-ZT with residue (ZT-ZT+R), and DSR and wheat both on permanent beds with residue (PB-PB+R). The ZT-ZT+R had the highest total SOC in both 0–15 and 15–30 cm soil layers (20% and 40% higher (p < .05) than CT-CT, respectively), whereas total SIC decreased by 11% and 15% in the respective layers under ZT-ZT+R compared with CT-CT. Non-labile SOC was the largest pool, followed by very labile, labile and less labile SOC. The benefits of ZT and residue retention were greatest for very labile SOC, which showed a significant (p < .05) increase (~50%) under ZT-ZT+R compared with CT-CT. The ZT-ZT+R sequestered ~2 Mg ha⁻¹ total SOC in the 0–15 cm soil layer in 6 years, where CT registered significant losses. Thus, the adoption of CA should be recommended in calcareous soils, for C sequestration, and also as a reclamation technique.     

A comparison between the walkley‐black and a dry combustion method for determining organic carbon in a humic brown soil,Papua New Guinea

Abstract

Regression equations for the relationship between Walkley‐Black carbon and carbon by dry combustion in a tropical humic brown clay soil were variable in four different vegetation regimes. In one case, statistically different correlation coefficients were obtained for grassland surface and the corresponding subsurface soils.

Calibration of the Walkley‐Black method against dry combustion carbon is recommended for each treatment in soil fertility studies as soil organic matter might have a different composition and hence carbon recovery value because of treatment.     

Analysis of cinnamaldehyde and diallyl disulfide as eco-pesticides in soils of different textures—a laboratory-scale mobility study

Journal of Soils and Sediments - This work presents for the first time the development of a method for the analysis of cinnamaldehyde and diallyl disulfide in soil by ultrasound assisted extraction...