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Aim This study aimed to simulate deactivation of Escherichia coli in soils amended with cattle manure after burning, anaerobic digestion, composting, or without treatment. Method and results The Weibull survival function was used to describe deactivation of E. coli. Parameters for each treatment were determined using E. coli measurements from manure-amended soils and evaluated against measurements at different application rates. A statistically significant correlation and high coincidence between the simulated and measured values were obtained. The simulations revealed that although anaerobic digestion or burning of cattle manure effectively reduced the E. coli loads to background levels, burning retained very little nitrogen, so the ash residue was ineffective as an organic fertilizer. Anaerobic digestion was most effective at reducing E. coli levels while retaining a high proportion of N in the bioslurry residue, but the persistence of E. coli was higher than in compost. Conclusion The results from this study suggest that the safest method for production of organic fertilizer would involve anaerobic digestion to reduce E. coli , followed by composting to reduce its persistence. [ABSTRACT FROM AUTHOR]

Our study measured heterotrophic carbon dioxide (CO2) emissions in a drained peatland under potato cultivation in south-western Uganda. Soil carbon losses have not previously been reported for this land use, and our study set out to capture the range and temporal variation in emissions, as well as investigate relationships with key environmental variables. Soil chamber-based emission measurements were taken over five days at four points in time over the year to capture daily and monthly variability, including day and night sampling to capture any diurnal variations in temperatures and soil flux. Differences in soil microtopography from mounding of soils for potato beds and drainage trenches had a significant effect on the rate of soil flux. Diurnal sampling showed no significant difference in emissions or soil temperatures in the raised potato beds between day and night. More significant effects on soil flux from environmental drivers, such as water table depth, were observed between months, rather than hours and days. There were significant differences in the relationships between environmental variables and soil flux, depending on if soils had been recently disturbed or not. Area-weighted emissions based on microtopography gave a mean annual emissions factor of 98.79 ± 1.7 t CO2 ha-1 y-1 (± standard error) from this peatland use. [ABSTRACT FROM AUTHOR]

Aim: This study investigated impacts of different organic waste treatment methods on reduction and spread of faecal indicator organisms to food crops in a developing country. Methods and Results: Fresh cattle manure was subjected to three different treatments; anaerobic digestion, burning and composting. Escherichia coli, coliforms and nitrogen content of cattle manure were measured before and after treatment in the amended soil and harvested lettuce. All treatments significantly reduced E. coli and coliform counts but differed in the ratio of E. coli or coliforms to nitrogen. Application of the recommended nitrogen dose of 120 kg ha−1 as bioslurry resulted in significantly lower E. coli and coliform contamination of soil than the same nitrogen rate applied as compost or ash. The E. coli content of lettuces grown on soil amended with treated wastes at recommended rates did not differ between treatments but was significantly lower than in lettuces grown on soil amended with untreated manure. Conclusions: Treatment of manure before use as an organic fertilizer significantly reduces potential contamination of both soil and food crops with E. coli and coliforms. To best reduce the spread of E. coli from organic fertilizers, manures should be treated by anaerobic digestion. Significance and Impact of the Study: Information from this study quantifies potential risks associated with use of manures in growing food crops by determining the ratio between pathogen content and required nitrogen application rate. [ABSTRACT FROM AUTHOR]

Replacement of forest by agricultural systems is a major factor accelerating the emissions of greenhouse gases; however, related field studies in the tropics are very scarce. To evaluate the impact of forest transition to plantations on soil methane (CH4) and respiration (CO2) fluxes, we conducted measurements in an undisturbed forest, a disturbed forest, young and old rubber plantations, and an oil palm plantation on mineral soil in Jambi, Sumatra, Indonesia. Methane fluxes and their controlling variables were monitored monthly over fourteen months; soil respiration was measured less frequently. All of the plantations were managed by smallholders and had never been fertilized. To assess the effect of common management practices in oil palm plantations, we added urea at a rate of 33.3 kg N/ha and thereafter monitored intensively soil CH4 fluxes. The soil acted as a sink for CH4(kg CH4-C·ha−1 ·yr−1 ) in the undisturbed forest (−1.4 ±1.0) and young rubber plantation (−1.7±0.7). This was not the case in the other land-use systems which had fluxes similar to fluxes in the undisturbed forest, with 0.4±0.9, −0.2±0.3, and 0.2±0.7 kg·ha−1 ·yr−1 in the disturbed forest, old rubber plantation, and oil palm plantation, respectively. In the oil palm plantation, there was no inhibitory effect of nitrogenous fertilizer on methanotrophy. Annual soil respiration (Mg CO2-C·ha−1 ·yr−1 ) was higher in the oil palm plantation (17.1±1.9) than in the undisturbed forest (13.9±1.2) while other land-use systems respired at a similar level to the undisturbed forest (13.1±1.4, 15.9 ±1.7, and 14.1±1.0 in the disturbed forest, young, and old rubber plantations, respectively). Substrate (litterfall and soil) availability and quality exerted a strong control over annual fluxes of both gases along the land-use gradient. Temporal variation in CH4 was extremely high and in respiration fluxes was moderate, but was not specifically linked to seasonal variation. Further comprehensive and long-term research is critically needed to determine more thoroughly the direction and magnitude of changes in soil trace gas emissions as affected by forest-to-plantation conversion in the tropics. [ABSTRACT FROM AUTHOR]

Field experiments were conducted at Gujjar Seed and Nursery Farm, Haripur, Pakistan to investigate impact of incorporating differently treated of organic manures using different tillage systems on soil carbon. Maximum increase in soil carbon was observed when the required nitrogen was applied as bioslurry produced from cattle manure by anaerobic digestion. This was significantly greater than when the required amount of nitrogen was applied as composted poultry manure or chemical fertilizer. Minimum tillage also resulted in a significant increase of soil carbon compared to conventional or deep tillage. These experimental measurements were used to evaluate a dynamic simulation model of soil organic matter turnover, RothC, which was then used to estimate future carbon sequestration. The correlation between experimental and simulated values was highly significant and the root mean square error was within experimental error, suggesting that RothC is providing an acceptable representation of the changes in soil carbon that is occurring in this experiment. The uncertainty in simulations was less than 3%. Simulations were done using future weather scenarios; these suggest that addition of the recommended rate of nitrogen in 8.4 t ha-1 y-1 bioslurry every year increases soil carbon sequestration over 100 years (2012-2112) by 24.9±0.74 t ha-1 compared to the control where no organic manure was applied. This sequesters 7.5±0.24 t ha-1 more carbon than if the same amount of nitrogen is applied as poultry manure, requiring an application rate of 7.5 t ha-1 y-1. If the same amounts of bioslurry and poultry manure are applied, carbon sequestration is still significantly greater for bioslurry than for poultry manure (4.5±0.2 t ha-1). Losses of carbon with climate change were highest under climate scenario B2 (environmental protection with regionalization) and B1 (environmental protection with globalization), followed by A1B (economic growth with globalization), with minimum losses from A2 (economic growth with regionalization). These predicted losses are likely to be more than compensated for by application of organic fertilizers at the rates needed to supply sufficient nitrogen to the crops. [ABSTRACT FROM AUTHOR]

We implemented a spatial application of a previously evaluated model of soil GHG emissions, ECOSSE, in the United Kingdom to examine the impacts to 2050 of land-use transitions from existing land use, rotational cropland, permanent grassland or woodland, to six bioenergy crops; three 'first-generation' energy crops: oilseed rape, wheat and sugar beet, and three 'second-generation' energy crops: Miscanthus, short rotation coppice willow ( SRC) and short rotation forestry poplar ( SRF). Conversion of rotational crops to Miscanthus, SRC and SRF and conversion of permanent grass to SRF show beneficial changes in soil GHG balance over a significant area. Conversion of permanent grass to Miscanthus, permanent grass to SRF and forest to SRF shows detrimental changes in soil GHG balance over a significant area. Conversion of permanent grass to wheat, oilseed rape, sugar beet and SRC and all conversions from forest show large detrimental changes in soil GHG balance over most of the United Kingdom, largely due to moving from uncultivated soil to regular cultivation. Differences in net GHG emissions between climate scenarios to 2050 were not significant. Overall, SRF offers the greatest beneficial impact on soil GHG balance. These results provide one criterion for selection of bioenergy crops and do not consider GHG emission increases/decreases resulting from displaced food production, bio-physical factors (e.g. the energy density of the crop) and socio-economic factors (e.g. expenditure on harvesting equipment). Given that the soil GHG balance is dominated by change in soil organic carbon ( SOC) with the difference among Miscanthus, SRC and SRF largely determined by yield, a target for management of perennial energy crops is to achieve the best possible yield using the most appropriate energy crop and cultivar for the local situation. [ABSTRACT FROM AUTHOR]

Author(s): Changming Fang; Pete Smith; John B. Moncrieff; Jo U. Smith Nature 433, 57-59 (2005) The x axis of Fig. 1 of this Letter was mislabelled. The correct tick labels [...]

We present results from modelling studies, which suggest that, at most, only about 10–20% of recently observed soil carbon losses in England and Wales could possibly be attributable to climate warming. Further, we present reasons why the actual losses of SOC from organic soils in England and Wales might be lower than those reported. [ABSTRACT FROM AUTHOR]

SummaryUnder the Kyoto Protocol, the European Union is committed to a reduction in CO2 emissions to 92% of baseline (1990) levels during the first commitment period (2008–2012). The Kyoto Protocol allows carbon emissions to be offset by demonstrable removal of carbon from the atmosphere. Thus, land-use/land-management change and forestry activities that are shown to reduce atmospheric CO2 levels can be included in the Kyoto targets. These activities include afforestation, reforestation and deforestation (article 3.3 of the Kyoto Protocol) and the improved management of agricultural soils (article 3.4). In this paper, we estimate the carbon mitigation potential of various agricultural land-management strategies and examine the consequences of European policy options on carbon mitigation potential, by examining combinations of changes in agricultural land-use/land-management. We show that no single land-management change in isolation can mitigate all of the carbon needed to meet Europe's climate change commitments, but integrated combinations of land-management strategies show considerable potential for carbon mitigation. Three of the combined scenarios, one of which is an optimal realistic scenario, are by themselves able to meet Europe's emission limitation or reduction commitments. Through combined land-management scenarios, we show that the most important resource for carbon mitigation in agriculture is the surplus arable land. We conclude that in order to fully exploit the potential of arable land for carbon mitigation, policies will need to be implemented to allow surplus arable land to be put into alternative long-term land-use. Of all options examined, bioenergy crops show the greatest potential for carbon mitigation. Bioenergy crop production also shows an indefinite mitigation potential compared to other options where the mitigation potential is finite. We suggest that in order to exploit fully the bioenergy option, the... [ABSTRACT FROM AUTHOR]

Water storage and flow in shallow subsurface drives runoff generation, vegetation water use and nutrient cycling. Modelling these processes under non-steady state conditions is challenging, particularly in regions like the subtropics that experience extreme wet and dry periods. At the catchment-scale, physically-based equations (e.g., Richards equation) are impractical due to their complexity, while conceptual models typically rely on steady state assumptions not found in daily hydrological dynamics. We addressed this by developing a simple modelling framework for shallow subsurface water dynamics based on physical relationships and a proxy parameter for the fluxes induced by non-unit hydraulic gradients. We demonstrate its applicability for six generic soil textures and for an Acrisol in subtropical China. Results showed that our new approach represents top soil daily fluxes and storage better than, and as fast as, standard conceptual approaches. Moreover, it was less complex and up to two orders of magnitude faster than simulating Richards equation, making it easy to include in existing hydrological models. [ABSTRACT FROM AUTHOR]

Low applications of inorganic fertilizer and decline in soil organic matter often contribute to loss of production in Sub-Saharan Africa. A trial was conducted on integrated soil fertility management of teff (Eragrostis tef) in Southern Ethiopia during the main cropping season of 2015. Treatments were based on recommended rates of inorganic fertilizer, applying organic fertilizer to provide the equivalent amount of N. Randomised treatments were replicated across six farms, including 100% as inorganic fertilizer, and inorganic and organic fertilizers in ratios 50:50, 67:33 and 33:67. All crop characteristics measured, except number of tillers and straw yield, showed statistically significant differences (p < 0.05). An inorganic-to-organic fertilizer ratio of 67:33 provided highest grain yield, while lowest total variable costs were obtained with the 33:67 ratio. Highest net benefit (520(±50) US$/ha) was obtained with the ratio 67:33, but the marginal rate of return over the 33:67 treatment was only 54(±8)%, and so did not provide sufficient return on the extra investment for inorganic fertilizer. Therefore, 33% inorganic fertilizer to 67% organic fertilizer is more economically viable. These trials demonstrate that, in addition to reducing long-term soil degradation, integrated soil fertility management can be an economically viable way of managing crops. [ABSTRACT FROM AUTHOR]

One of the main options for carbon mitigation identified by the IPCCis the sequestration of carbon in soils. In this paper we use statistical relationships derived from European long-term experiments to explore the potential for carbon sequestration in soils in the EuropeanUnion. We examine five scenarios, namely (a) the amendment of arablesoils with animal manure, (b) the amendment of arable soils with sewage sludge, (c) the incorporation of cereal straw into the soils in which it was grown, (d) the afforestation of surplus arable land through natural woodland regeneration, and (e) extensification of agriculture through ley-arable farming. Our calculations suggest only limitedpotential to increase soil carbon stocks over the next century by addition of animal manure, sewage sludge or straw (less than 15 Tg C y{sup}-1{end}), but greater potential through extensification of agriculture (~~ 40 Tg C y{sup}-1{end}) or through the afforestation of surplus arable land (~~ 50 Tg C y{sup}-1{end}). We estimate that extensification could increase the total soil carbon stock of the European Union by 17%. Afforestation of 30% of present arable land would increase soil carbon stocks by about 8% over a century and would substitute up to 30 Tg C y{sup}-1{end} of fossil fuel carbon if the wood were used as biofuel. However, even the afforestation scenario, with the greatest potential for carbon mitigation, can sequester only 0.8% of annual global anthropogenic CO{sub}2{end}-carbon. Our figures suggest that, although efforts in temperate agriculture can contribute to global carbon mitigation, the potential is small compared to that available through reducing anthropogenic CO{sub}2{end} emissions by halting tropical and sub-tropical deforestation or by reducing fossil fuel burning. [ABSTRACT FROM AUTHOR]