Assessment of soil organic matter supply: Challenges and opportunities

Soil organic matter (SOM) is recognized as an important factor for sustainable land use. Several analyzing techniques were focused on fractionation of soil organic carbon (SOC), on carbon sequestration, soil functions, or other approaches. We combined SOC fractionation with studies on carbon sequestration. Thermogravimetry (TG, recording of mass losses during heating up of soil samples) was selected as a supplemental method to standard analyzing techniques for soils. TG provides recording of thermal mass losses in dependency on temperature what facilitate fractionation together with SOM content determination via mass losses on ignition (MLI). Autocorrelation analyses of TG data enable to assess the carbon sequestration processes. After a gentle sample preparation, more than 370 soil samples in eight sample sets were analyzed from different types of soils and regions of origin. The results extend literature data by revealing quantifiable interrelations between content of SOM, SOC and clay with a coefficient of determination around 0.98. Deviations from the relationship become lower during incubation experiments, with increasing sampling depth, and with decreasing organic fertilization in plots of long term agriculture field experiments etc. We explained these results with changing quantities of extraneous (mostly fresh) organic residues not affected by soil carbon content regulation. These organic residues seems to be quantifiable via difference between measured MLI and the MLI calculated from content of SOC and clay both determined by standard methods. The practical use of found interrelation implies an acceptance of traditional definition of soil and SOM as products of long term ecosystem succession with content regulation as a unifying over regions soil feature. In contrast, the more common and simplified understanding of soil as carbon containing mineral substrates supports public recognition of soils. However, it does not facilitate the comparison of results from different regions and studies about soils. We conclude from these considerations about obligatory distinction between following types of organic carbon as an essential precondition for assessment of SOM supply: 1. SOC (or humus) as a product of long term carbon regulation processes, 2. fresh organic residues, and carbon of 3. geologic (turf, coal, graphite, diamond, …) or 4. anthropogenic origin (black carbon in ashes, cinder, soot, asphalt)

Occurrence and functioning of phosphate solubilizing microorganisms from oil palm tree (Elaeis guineensis) rhizosphere in Cameroon

Phosphorus replenishment, particularly in smallholder agriculture, remains a challenge as it is mainly fertilizer dependent. While the use of soluble mineral phosphate fertilizers is the obvious best means tocombat phosphate deficiency in Cameroon, their use is limited by their high cost and availability at farmer’s level. This study was aimed at maintaining the fertility of Cameroon soils by biological means,in order to improve agricultural production, using low inputs technology. Isolates were obtained from oil palm tree (Elaeis guineensis) root fragments and rhizospheric soils and their activity in mobilizingphosphate from insoluble sources was evaluated on agar plates and liquid culture media containing sparingly soluble phosphates. At the end of incubation time, it appeared that, phosphate solubilizationresulted from a combined effect of pH decrease of the media and organic acids production. Furthermore, each of the tested isolates was able to produce at least one of the most important organic acids such as citrate, malate and tartrate. Among the ten isolates tested, three were identified as Pseudomonas fluorescens and would be considered as potential biofertilizers

Organic carbon content determination in soils: challenges and opportunities of elemental analysis versus thermogravimetry

Sustainable soil management needs reliable and accurate monitoring of soil organic carbon (SOC) content. However, despite of the development of analytical techniques during last decades, the detection opportunities for short term and rather small changes in SOC induced by organic fertilization, organic amendments or land use changes are still limited with the available methods. This study aims to quantify the theoretical detection opportunities for changes in SOC content with elemental analysis (EA) as the standard method in comparing with thermogravimetry (TG) as an enhanced traditional approach derived from soil organic matter determination via mass losses on ignition. The carried out experiments consist of mixing soil samples from non-fertilized plots of three long-term agricultural experiments in Bad Lauchstaedt, Großbeeren and Muencheberg (silty loam, loamy sand and silty sand) with straw, farmyard manure, sheep faeces and charcoal in four quantities (3 t×ha-1, 20 t×ha-1, 60 t×ha-1 and 180 t×ha‑1fresh matter) under laboratory conditions.The quantities were based on fresh matter application in agricultural practice accepting different amounts of added organic carbon. The results confirm EA as a method of higher reliability and accuracy for carbon content determination. TG allows to distinguish the different types of added amendments with high sensitivity. This was achieved by using newly developed evaluation algorithms for the thermal decay dynamics. We conclude from these results that TG cannot substitute EA to determine organic carbon on a routine base. However, TG could be a supplementary fingerprinting technique for the detection of added organic carbon to soils from organic fertilizers and to distinguish sources of geological or anthropogenic origin enabling a future assessment of soil organic carbon quality

The legacy effect of synthetic N fertiliser

Cumulative crop recovery of synthetic fertiliser nitrogen (N) over several cropping seasons (legacy effect) generally receives limited attention. The increment in crop N uptake after the first-season uptake from fertiliser can be expressed as a fraction (∆RE) of annual N application rate. This study aims to quantify ∆RE using data from nine long-term experiments (LTEs). As such, ∆RE is the difference between first season (RE1st) and long-term (RELT) recovery of synthetic fertiliser N. In this study, RE1st was assessed either by the 15N isotope method, or by a zero-N subplot freshly superimposed on a long-term fertilised LTE treatment plot. RELT was calculated by comparing N uptake in the total aboveground crop biomass between a long-term fertilised and long-term control (zero-N) treatment. Using a mixed linear effect model, the effects of climate, crop type, experiment duration, average N rate, and soil clay content on ∆RE were evaluated. Because the experimental setup required for calculation of ∆RE is relatively rare, only nine suitable LTEs were found. Across these nine LTEs in Europe and North America, mean ∆RE was 24.4% (±12.0%, 95% CI) of annual N application, with higher values for winter wheat than for maize. This result shows that fertiliser-N retained in the soil and stubble may contribute substantially to crop N uptake in subsequent years. Our results suggest that an initial recovery of 43.8% (±11%, 95% CI) of N application may increase to around 66.0% (±15%, 95% CI) on average over time. Furthermore, we found that ∆RE was not clearly related to long-term changes in topsoil total N stock. Our findings show that the - often used - first year recovery of synthetic fertiliser N application does not express the full effect of fertiliser application on crop nutrition. The fertiliser contribution to soil N supply should be accounted for when exploring future scenarios on N cycling, including crop N requirements and N balance schemes

Soft systems methodology: a context within a 50-year retrospective of OR/MS

Soft systems methodology (SSM) has been used in the practice of operations research and management science OR/MS) since the early 1970s. In the 1990s, it emerged as a viable academic discipline. Unfortunately, its proponents consider SSM and traditional systems thinking to be mutually exclusive. Despite the differences claimed by SSM proponents between the two, they have been complementary. An extensive sampling of the OR/MS literature over its entire lifetime demonstrates the richness with which the non-SSM literature has been addressing the very same issues as does SSM

Manuring and stable nitrogen isotope ratios in cereals and pulses: towards a new archaeobotanical approach to the inference of land use and dietary practices

This paper explores the impact of animal manure application on the δ15N values of a broad range of crops (cereals and pulses), under a range of manuring levels/regimes and at a series of locations extending from northwest Europe to the eastern Mediterranean. We included both agricultural field experiments and areas where ‘traditional’ farming is practised. Our aim is to ground-truth interpretation of δ15N values in archaeobotanical crop remains as evidence of past growing conditions and husbandry practices. The results confirm the potentially radical impact of manuring on δ15N values in cereals, depending on manuring level, but indicate only a slight effect on pulses, which can fix atmospheric nitrogen. The expected geographical trend towards greater δ15N with increasing climatic aridity is not apparent, probably because the growing conditions for crops are ‘buffered’ through crop management. Each of these observations has fundamental implications for archaeobotanical interpretation of δ15N values as evidence of land use practices and (together with analysis of bone collagen/tooth enamel in potential consumers) palaeodiet

The effect of rural-to-urban migration on social capital and common mental disorders: PERU MIGRANT study

OBJECTIVE: This study aims to investigate whether there are differences in the prevalence of common mental disorders and social capital between migrant and non-migrant groups in Peru. METHODOLOGY: The PERU MIGRANT study is a cross-sectional study comprising three groups: an urban group from a shanty town in Lima; a rural group from a community in Ayacucho-Peru; and a migrant group originally from Ayacucho currently living in the same urban shanty town. Common mental disorders were assessed using the General Health Questionnaire (GHQ-12), and social capital was assessed using the Short Social Capital Assessment Tool (SASCAT). Poisson regression with robust standard errors was used to estimate prevalence ratios. RESULTS: The overall prevalence of common mental disorders was 39.4%; the highest prevalence was observed in the rural group. Similar patterns were observed for cognitive social capital and structural social capital. However after adjustment for sex, age, family income and education, all but one of the significant relationships was attenuated, suggesting that in this population migration per se does not impact on common mental health disorders or social capital. CONCLUSIONS: In the PERU MIGRANT study, we did not observe a difference in the prevalence of common mental disorders, cognitive and structural social capital between migrant and urban groups. This pattern of associations was also similar in rural and urban groups, except that a higher prevalence ratio of structural social capital was observed in the rural group

Physicochemical Characterization, and Relaxometry Studies of Micro-Graphite Oxide, Graphene Nanoplatelets, and Nanoribbons

The chemistry of high-performance magnetic resonance imaging contrast agents remains an active area of research. In this work, we demonstrate that the potassium permanganate-based oxidative chemical procedures used to synthesize graphite oxide or graphene nanoparticles leads to the confinement (intercalation) of trace amounts of Mn2+ ions between the graphene sheets, and that these manganese intercalated graphitic and graphene structures show disparate structural, chemical and magnetic properties, and high relaxivity (up to 2 order) and distinctly different nuclear magnetic resonance dispersion profiles compared to paramagnetic chelate compounds. The results taken together with other published reports on confinement of paramagnetic metal ions within single-walled carbon nanotubes (a rolled up graphene sheet) show that confinement (encapsulation or intercalation) of paramagnetic metal ions within graphene sheets, and not the size, shape or architecture of the graphitic carbon particles is the key determinant for increasing relaxivity, and thus, identifies nano confinement of paramagnetic ions as novel general strategy to develop paramagnetic metal-ion graphitic-carbon complexes as high relaxivity MRI contrast agents

The influence of external factors on bacteriophages—review

The ability of bacteriophages to survive under unfavorable conditions is highly diversified. We summarize the influence of different external physical and chemical factors, such as temperature, acidity, and ions, on phage persistence. The relationships between a phage’s morphology and its survival abilities suggested by some authors are also discussed. A better understanding of the complex problem of phage sensitivity to external factors may be useful not only for those interested in pharmaceutical and agricultural applications of bacteriophages, but also for others working with phages

Anthropogenic CO₂ Inventory of the Indian Ocean

This study presents basin-wide anthropogenic CO2 inventory estimates for the Indian Ocean based on measurements from the World Ocean Circulation Experiment/Joint Global Ocean Flux Study global survey. These estimates employed slightly modified ΔC* and time series techniques originally proposed by Gruber et al. [1996] and Wallace [1995], respectively. Together, the two methods yield the total oceanic anthropogenic CO2 and the carbon increase over the past 2 decades. The highest concentrations and the deepest penetrations of anthropogenic carbon are associated with the Subtropical Convergence at around 30° to 40°S. With both techniques, the lowest anthropogenic CO2 column inventories are observed south of 50°S. The total anthropogenic CO2 inventory north of 35°S was 13.6±2 Pg C in 1995. The inventory increase since GEOSECS (Geochemical Ocean Sections Program) was 4.1±1 Pg C for the same area. Approximately 6.7±1 Pg C are stored in the Indian sector of the Southern Ocean, giving a total Indian Ocean inventory of 20.3 ±3 Pg C for 1995. These estimates are compared to anthropogenic CO2 inventories estimated by the Princeton ocean biogeochemistry model. The model predicts an Indian Ocean sink north of 35°S that is only 0.61–0.68 times the results presented here; while the Southern Ocean sink is nearly 2.6 times higher than the measurement-based estimate. These results clearly identify areas in the models that need further examination and provide a good baseline for future studies of the anthropogenic inventory