Ecosystem services in smallholder coffee farming systems: a case study in Uganda using chemical soil indicators

Farmers in coffee producing countries may not be aware of the economic, social and ecological benefits available through organic agriculture. At a local, regional and global scale, smallholder coffee farmers can discover that organic production methods are linked to provisioning, regulating, cultural and supporting ecosystem services. It is assumed that organic agriculture has a significant influence on soil parameters, and by association, on ecosystem services. Differences between farming systems in soil chemical properties reveal advantages for coffee farmers and shows the ecosystem services derived through organic agriculture at a local level. Benefits discovered in organic coffee systems are higher inputs of organic matter, higher biodiversity of soil microorganisms, less soil erosion, and the potential for higher aggregate stability and superior nutrient circulation

Quality assessment of meta-analyses on soil organic carbon

Soil organic carbon (SOC) plays a vital role in the global carbon cycle and is a potential sink for carbon dioxide. Agricultural management practices can support carbon sequestration and, therefore, offer potential removal strategies whilst also improving overall soil quality. Meta-analysis allows one to summarize results from primary articles by calculating an overall effect size and to reveal the source of variation across studies. The number of meta-analyses published in the field of agriculture is continuously rising. At the same time, more and more articles refer to their synthesis work as a meta-analysis, despite applying less than rigorous methodologies. As a result, poor-quality meta-analyses are published and may lead to questionable conclusions and recommendations to scientists, policymakers, and farmers. This study aims at quantitatively analyzing 31 meta-analyses, published between the years of 2005 and 2020, studying the effects of different management practices on SOC. We compiled a set of quality criteria suitable for soil and agricultural sciences by adapting existing meta-analytical guidelines from other disciplines. The set is supported by a scoring scheme that allows for a quantitative analysis. The retrieved meta-analyses were structured according to 11 management categories, such as tillage, cover crops, crop residue management, and biochar application, which allowed us to assess the state of knowledge on these categories. Major deficiencies were found in the use of standard metrics for effect size calculation, independence of effect sizes, standard deviation extraction for each study, and study weighting by the inverse of variance. Only 1 out of 31 SOC meta-analyses, which studied the effects of no tillage/reduced tillage compared with conventional tillage, was found to be of high quality. Therefore, improved meta-analyses on the effects of organic agriculture, biochar, fertilization, or crop diversification on SOC are urgently needed. We conclude that, despite efforts over the last 15 years, the quality of meta-analyses on SOC research is still low. Thus, in order for the scientific community to provide high-quality synthesis work and to make advancements in the sustainable management of agricultural soils, we need to adapt rigorous methodologies of meta-analysis as quickly as possible

Meta-analysis protocol on the effects of cover crops on pool specific soil organic carbon

Soil organic carbon (SOC) plays an important role in agricultural soils, as it contributes to overall soil health as well as climate change mitigation and adaptation. By conducting a meta-analysis, we aim to quantitatively summarize research studying the effects of cover crops (CC) on SOC pools throughout soil depths in arable cropland. We included global studies located in the climatic zones present in Europe. The pools chosen for this analysis are the particulate organic carbon (POC) and the mineral associated organic carbon (MAOC) and the microbial biomass carbon (MBC). Alongside, we will study the effects of a broad range of moderators, such as pedo-climatic factors, other agricultural management practices and CC characteristics e.g., type. We identified 71 relevant studies from 61 articles, of which mean values for SOC pools, standard deviations and sample sizes for treatments (CC) and controls (no CC) were extracted. To perform the meta-analysis, an effect size will be calculated for each study, which will then be summarized across studies by using weighing procedure. Consequently, this meta-analysis will provide valuable information on the state of knowledge on SOC pool change influenced by CC, corresponding quantitative summary results and the sources of heterogeneity influencing these results. Graph

Microbial functionality as affected by experimental warming of a temperate mountain forest soil—A metaproteomics survey

Soil microbes play an important role in terrestrial carbon (C) cycling, but their functional response to global warming remains yet unclear. Soil metaproteomics has the potential to contribute to a better understanding of warming effects on soil microbes as proteins specifically represent active microbes and their physiological functioning. To quantify warming effects on microbial proteins and their distribution among different functional and phylogenetic groups, we sampled forest soil that had been artificially warmed (+4 °C) during seven consecutive growing seasons and analyzed its metaproteomic fingerprint and linked to soil respiration as a fundamental ecosystem service. Bacterial protein abundances largely exceeded fungal abundances at the study site but protein abundances showed only subtle differences among control and warmed soil at the phylum and class level, i.e. a temperature-induced decrease in Firmicutes, an increase in Agaricomycetes and Actinobacteria, and a decrease in the Asco/Basidiomycota ratio. Community function in warmed soil showed a clear trend towards increased proteins involved in microbial energy production and conversion, related to the increased CO2 efflux from warmed soil as a result of stress environmental conditions. The differences in community function could be related to specific phyla using metaproteomics, indicating that microbial adaptation to long-term soil warming mainly changed microbial functions, which is related to enhanced soil respiration. The response of soil respiration to warming (+35% soil CO2 efflux during sampling) has not changed over time. Accordingly, potential long-term microbial adaptations to soil warming were too subtle to affect soil respiration rates or, were overlaid by other co-varying factors (e.g. substrate availability)

Gross Ammonification and Nitrification Rates in Soil Amended with Natural and NH4-Enriched Chabazite Zeolite and Nitrification Inhibitor DMPP

Using zeolite-rich tuffs for improving soil properties and crop N-use efficiency is becoming popular. However, the mechanistic understanding of their influence on soil N-processes is still poor. This paper aims to shed new light on how natural and NH4+-enriched chabazite zeolites alter short-term N-ammonification and nitrification rates with and without the use of nitrification inhibitor (DMPP). We employed the 15N pool dilution technique to determine short-term gross rates of ammonification and nitrification in a silty-clay soil amended with two typologies of chabazite-rich tuff: (1) at natural state and (2) enriched with NH4+-N from an animal slurry. Archaeal and bacterial amoA, nirS and nosZ genes, N2O-N and CO2-C emissions were also evaluated. The results showed modest short-term effects of chabazite at natural state only on nitrate production rates, which was slightly delayed compared to the unamended soil. On the other hand, the addition of NH4+-enriched chabazite stimulated NH4+-N production, N2O-N emissions, but reduced NO3-N production and abundance of nirS-nosZ genes. DMPP efficiency in reducing nitrification rates was dependent on N addition but not affected by the two typologies of zeolites tested. The outcomes of this study indicated the good compatibility of both natural and NH4+-enriched chabazite zeolite with DMPP. In particular, the application of NH4 +-enriched zeolites with DMPP is recommended to mitigate short-term N losses

Nitrous oxide emissions from soils: how well do we understand the processes and their controls?

Although it is well established that soils are the dominating source for atmospheric nitrous oxide (N2O), we are still struggling to fully understand the complexity of the underlying microbial production and consumption processes and the links to biotic (e.g. inter- and intraspecies competition, food webs, plant–microbe interaction) and abiotic (e.g. soil climate, physics and chemistry) factors. Recent work shows that a better understanding of the composition and diversity of the microbial community across a variety of soils in different climates and under different land use, as well as plant–microbe interactions in the rhizosphere, may provide a key to better understand the variability of N2O fluxes at the soil–atmosphere interface. Moreover, recent insights into the regulation of the reduction of N2O to dinitrogen (N2) have increased our understanding of N2O exchange. This improved process understanding, building on the increased use of isotope tracing techniques and metagenomics, needs to go along with improvements in measurement techniques for N2O (and N2) emission in order to obtain robust field and laboratory datasets for different ecosystem types. Advances in both fields are currently used to improve process descriptions in biogeochemical models, which may eventually be used not only to test our current process understanding from the microsite to the field level, but also used as tools for up-scaling emissions to landscapes and regions and to explore feedbacks of soil N2O emissions to changes in environmental conditions, land management and land use

The Application of ecological stoichiometry to plant-microbial-soil organic matter transformations

L'apèndix està disponible en línia a http://dx.doi.org/10.1890/14-0777.1.smEl títol del post-print és The Application of ecological stoichiometry to microbial decomposition: from plants to microbial communitiesAquest treball també ha rebuts els ajuts següents: MICDIF integrated project (linking microbial diversity and function across scales and ecosystems), funded by the Austrian Science Fund FWF (S 10006-B01, S 10006-B06, S 10006- B07)Elemental stoichiometry constitutes an inherent link between biogeochemistry and the structure and processes within food webs, and thus is at the core of ecosystem functioning. Stoichiometry allows for spanning different levels of biological organization, from cellular metabolism to ecosystem structure and nutrient cycling, and is therefore particularly useful for establishing links between different ecosystem compartments. We review elemental carbon : nitrogen : phosphorus (C:N:P) ratios in terrestrial ecosystems (from vegetation, leaf litter, woody debris, and dead roots, to soil microbes and organic matter). While the stoichiometry of the plant, litter, and soil compartments of ecosystems is well understood, heterotrophic microbial communities, which dominate the soil food web and drive nutrient cycling, have received increasing interest in recent years. This review highlights the effects of resource stoichiometry on soil microorganisms and decomposition, specifically on the structure and function of heterotrophic microbial communities and suggests several general patterns. First, latitudinal gradients of soil and litter stoichiometry are reflected in microbial community structure and function. Second, resource stoichiometry may cause changes in microbial interactions and community dynamics that lead to feedbacks in nutrient availability. Third, global change alters the C:N, C:P, and N:P ratios of primary producers, with repercussions for microbial decomposer communities and critical ecosystem services such as soil fertility. We argue that ecological stoichiometry provides a framework to analyze and predict such global change effects at various scales

Quantifying nitrogen fluxes and their influence on the greenhouse gas balance: recent findings of the NitroEurope Integrated Project

The generation of reactive nitrogen (Nr) by human activities to stimulate agricultural productivity and the unintended formation of Nr in combustion processes both have major impacts on the global environment. Effects of excess Nr include the deterioration of air quality, water quality, soil quality and a decline in biodiversity. One of the most controversial impacts of nitrogen, however, is on the greenhouse gas balance. While recent papers have highlighted a possible benefit of nitrogen in enhancing rates of carbon sequestration, there remain many trade-offs between nitrogen and greenhouse gas exchange. The result is that the net effect of Nr on the global radiative balance has yet to be fully quantified. To better understand these relationships requires intense measurement and modelling of Nr fluxes at various temporal and spatial scales in order to make the link between different nitrogen forms and their fate in the environment. It is essential to measure fluxes for a wide range of ecosystems considering the biosphere-atmosphere exchange of the Nr components and greenhouse gases, as well as the fixation of di-nitrogen and its creation by denitrification. Long-term observations are needed for representative ecosystems, together with results from experiments addressing the responses of the key nitrogen and greenhouse gas fluxes to different global change drivers. The NitroEurope Integrated Project (in short NEU IP), funded under the 6th Framework Programme of the European Commission, has developed and applied a strategy for quantifying these different terms on multiple scales. With the project nearing completion, this presentation reports selected preliminary findings. It highlights the first estimates of Nr inputs and net green-house gas exchange for a series of 13 flux ‘supersites’, complemented by the emerging results of Nr concentrations and related N inputs at a network of 58 ‘inferential sites’, which extend the European representativity of the results. In addition, new low cost methods to measure nitrogen fluxes will be reported, which have been extensively tested at those sites. Results from this 3-tier flux network are underpinned by emerging findings from an extensive network of manipulation sites. A combination of modelling at plot, landscape and European scales is used to upscale the results. Finally the talk will illustrate how nitrogen mitigation techniques are being considered at the European scale, including an estimation of the scale of costs involved in simultaneously mitigating nitrous oxide, ammonia and nitrate losse