Management Practices In Agroecosystems Research Articles

Reconciling plant and microbial ecological strategies to elucidate cover crop effects on soil carbon and nitrogen cycling

Abstract Plant economics, the way plants allocate and utilize resources, affect multiple soil processes through interactions with root and associated microbial communities. However, the interplay between plant economics and microbial ecological strategies remains poorly understood, which is crucial for integrated manipulation of plant‐ and microbe‐mediated functions in mitigating climate change and sustaining soil health. We used a field experiment with 11 cover crop species grown monocultures in the same base soil to test whether microbial ecological strategies are associated with plant economic strategies and if their interactions are linked to soil functions. A principal component analysis (PCA) was performed on root and leaf traits to identify the loadings of cover crop species on the plant trait space. Metagenomic analysis of rhizosphere microbial communities was conducted to infer their ecological strategies based on genetically encoded community‐aggregated traits. We found a synchronous relationship between the conservation gradient of plant economic strategies and the trade‐offs in microbial ecological strategies. Conservative plant strategists, such as Lolium multiflorum, Triticum turgidum and Brassica juncea, fostered microbial communities characterized by high growth yield potentials (Y‐strategies). This included increased microbial carbon fixation pathways, citrate cycle, ribosome and valine, leucine and isoleucine biosynthesis. As a result, microbial metabolic efficiency improved, shown by higher microbial biomass carbon content and a lower metabolic quotient (qCO2), led to enhanced soil organic carbon accumulation. In comparison, acquisitive plants like Astragalus sinicus, Vicia villosa, Trifolium incarnatum and Medicago sativa stimulated microbial resource‐acquisition strategies (A‐strategies). This included enhanced bacterial chemotaxis, secretion systems, biotin metabolism and cell motility pathways, which in turn increased soil exoenzyme activity and accelerated soil nitrogen mineralization. Consequently, these species enhanced soil nitrogen availability and had substantial feedbacks on subsequent main crop productivity. Synthesis. This study demonstrates how plant economic strategies influence the balance between different microbial ecological strategies, specifically the trade‐offs in Y‐ and A‐strategies. These interactions exert control over carbon and nitrogen dynamics in the soil ecosystem. The findings provide insights for implementing nature‐based solutions to improve agroecosystem management practices.

The Role of Plant-Mycorrhizal-Fungal Interactions in Soil Health and Carbon Sequestration in Agroecosystems

Abstract: Understanding the intricate interactions between plants, mycorrhizal fungi, and soil health is crucial for sustainable agriculture and climate change mitigation. This review synthesizes current research to elucidate the multifaceted role of plantmycorrhizal-fungal interactions in soil health and carbon sequestration in agroecosystems. A meta-analysis of 75 studies spanning diverse ecosystems and plant species reveals a significant positive correlation between mycorrhizal colonization and soil organic carbon content, with an average increase of 25% compared to non-mycorrhizal systems. Furthermore, mycorrhizal symbiosis enhances soil structure and aggregation, promoting water retention and nutrient cycling, which are essential for maintaining soil fertility and resilience to environmental stressors. The contributions of different mycorrhizal types (arbuscular, ectomycorrhizal, and ericoid) to soil carbon dynamics are also examined, highlighting their unique roles in carbon allocation and stabilization. Additionally, the review discusses the potential implications of plant-mycorrhizal-fungal interactions for mitigating greenhouse gas emissions through enhanced carbon sequestration in agricultural soils. Insights into the mechanisms underlying these interactions, including mycorrhizal-mediated changes in root exudates, microbial communities, and soil enzymatic activities, are discussed. Overall, this review underscores the importance of integrating mycorrhizal symbiosis into agroecosystem management practices to enhance soil health, carbon sequestration, and climate resilience.

Compost and biosolids increase long-term soil organic carbon stocks

Biobased residues derived from organic urban waste materials can be processed to produce soil amendments that enhance soil fertility and carbon sequestration. However, the extent of carbon sequestration by biobased residues depends on the interaction between their physicochemical properties, climate, and agroecosystem management practices. Our objective was to predict how different biobased residues (compost, anaerobic digestate, or biosolids), compared to nitrogen fertilizer, affect soil organic carbon stocks under continuous cropping and crop rotation in Ontario, Canada, using the Century model. The Century model was calibrated and validated with data, from a three-year field study located in Elora, Ontario, Canada, that was used to predict long-term changes in soil organic carbon. Our results showed that after 150 years, soil amended with compost and biosolids increased soil organic carbon stocks significantly ( p < 0.05) compared to anaerobic digestate and nitrogen fertilizer. Soil organic carbon stocks were 1%–27% greater with crop rotation compared to continuous cropping. Model performance indicated a strong correlation between measured and simulated soil organic carbon stocks ( R2 = 0.26–0.82; RMSD = 432–727 g m−2). Our findings suggested that compost had the greatest soil carbon sequestration potential of the tested soil amendments, and this difference was due to the quantity and quality of carbon input.

Carabid Beetles (Coleoptera) as Indicators of Sustainability in Agroecosystems: A Systematic Review.

The sustainability of agroecosystems is at risk owing to continuous anthropogenic disturbance. As such, there is a need to evaluate indicator taxa that may be used to monitor the health of agricultural management systems. Carabid beetles are ubiquitous and functionally crucial in agroecosystems while at the same time are sensitive to the changes caused by management practices. Their quick response to anthropogenic disturbances has been proposed as a practical and realistic tool for monitoring the sustainability of agricultural practices. However, there is still disagreement about carabids as possible indicators of agroecosystem sustainability. We conducted a systematic review of the responses of carabid beetles to agricultural systems in different biogeographical areas. We examined whether these beetles could serve as potential indicators of agroecosystem sustainability. The ISI Web of Science, Google Scholar, and Scopus were used to search for papers published from 2000-2019. In total, we included 69 studies indicating the use of carabids to monitor the impact of management practices in agroecosystems. Most studies were conducted in European countries (n = 37), while Southern Africa and East Asia countries were significantly under-represented (n = 10). Carabid beetle response to agroecosystems varied between management practices, with biodiversity indices (n = 41: positive 60%, negative 19%, and neutral 19%) being the most measured response variable, followed by functional diversity (n = 28: positive 67%, negative 25%, and neutral 7%). Overall, our findings highlight the need for more research in underdeveloped countries, to investigate the potential of overlooked carabids and include response variables measuring functional diversity in assessing the sustainability of agricultural management. This will assist policy makers and land managers in making active and informed decisions about agroecological disturbances and management.

Evaluation of nitrous oxide emissions from vineyard soil: Effect of organic fertilisation and tillage

It is well known that the largest source of N2O is the agricultural sector, where fertilization represents the main source of this GHG. Monitoring N2O fluxes for different soil management and crops type is essential to define better N management practices in agro-ecosystems. However, scarce studies have been published about field measurements of organic fertilizers effects in orchards and vineyards.In this paper we present the first long-term high-resolution study on N2O emissions in a vineyard, in temperate climate. The use of dynamic chambers connected directly to an IRGA, allowed to collect one year (from May 2018 to May 2019) of measurements at time resolution of 2 h. The aim of the study was to assess the effect of organic fertilization (compost) and tillage on N2O emissions. Emission factors of uncorrected (EFt) and corrected for no-fertilizer induced emissions (EFf) were calculated.Results showed a seasonal trend in N2O fluxes, with higher base fluxes and peaks during the warm season and in correspondence of rainy events. Emission peak linked to fertilizer application occurred during the first 6–7 days after treatment followed by a decrease in N2O fluxes. Cumulated annual emissions varies between 0.54 and 1.38 kg N2O–N ha−1 y−1, depending on treatment and level of soil TOC content. The uncorrected EF was between 0.4 and 0.9% of N input, in line with the IPCC value for organic fertilizers in wet climate, while the EFf (referred only to direct fertilizer application) were in range of 0.02–0.4% of N input. We found EFf of fertilized not tilled treatments from 17 to 79% lower than fertilized tilled, with different magnitude of reduction depending on soil TOC. Our EFt were in line with disaggregated EFs from IPCC 2019 but EFf were 43% lower on average, confirming the IPCC reference value to be a good estimator of the overall N2O emissions from organic fertilized soil, but too high for the estimation of only fertilizer application emissions.These results are of remarkable importance to direct organic fertilization management and related policies towards more environmentally sustainable approaches.

Tillage intensity and plant rhizosphere selection shape bacterial-archaeal assemblage diversity and nitrogen cycling genes

Agroecosystem management practices, plant-microbe interactions, and climate are all factors that influence soil microbial community diversity and functionality. Herein, we assessed diversity of soil bacterial-archaeal assemblages and denitrification gene markers in a long-term tillage field experiment. We evaluated bulk and rhizosphere soils from two crop years (corn and soybean) of a three-year rotation of corn-soybean-small grain + cover crop. Soil samples were collected at three growth stages from corn and soybean plants and across three tillage practices that had been applied every year for 40 years. Tillage practices represented three levels of disturbance intensity ranging from low (no-till) to intermediate (chisel-disk) to high (moldboard plow) intensities. Bacterial assemblage diversity differed in soils having contrasting tillage histories and from bulk or rhizosphere soil (compartments), crop year, and growth stage. Compared to plowed and chisel-disked soils, no-till soils had lower abundances of denitrification genes, higher abundances of genes for dissimilatory nitrate reduction to ammonium (DNRA), and higher abundances of family-level taxa associated with archaeal nitrification and anammox. Soybean rhizospheres exerted stronger selection on bacterial-archaeal composition and diversity relative to corn rhizospheres. Abundances of N genes were grouped by factors related to weather, as well as management and soil compartment, which could impact activity related to denitrification and DNRA. Low intensity tillage may provide an option to reduce potential ‘hot spots’ or ‘hot moments’ for N losses in agricultural soils, although weather and crop type are also important factors that can influence how tillage affects microbial assemblages and microbial N use.

Documenting pollinators, floral hosts, and plant-pollinator interactions in U.S. Pacific Northwest agroecosystems.

The abundance and diversity of pollinator populations are in global decline. Managed pollinator species, like honey bees, and wild species are key ecosystem service providers in both natural and managed agroecosystems. However, relatively few studies have exhaustively characterized pollinator populations in diverse agroecosystems over multiple years, while also thoroughly documenting plant-pollinator interactions. Yet, such studies are needed to fulfill the national pollinator protection plans that have been released by the United States and other nations. Our research is among the first studies to respond to these directives by systematically documenting bee and plant biodiversity, bee-plant interactions, and bee-mediated pollen movement in farming systems of the Pacific Northwest, USA. Our data provides insight into the processes mediating pollinator and plant community assembly, persistence, and resilience across landscapes with variable crop and landscape diversity and agroecosystem management practices. These data will also contribute to the development of a United States pollinator database, supporting the United States' plan to promote pollinators. With few publicly available data sets that systematically take account of agroecosystem practices, plant populations, and pollinators, our research will provide future users the means to conduct synesthetic studies of pollinators and ecosystem function in a period of rapid and global pollinator declines. There are no copyright or proprietary restrictions for research or teaching purposes. Usage of the data set must be cited.

315 Formation, persistence, and function of soil organic matter: how recent scientific advances apply in agroecosystems

Abstract Soil organic matter is fundamental to healthy and productive soils and building it is an effective means by which to draw down atmospheric greenhouse gas concentrations with added co-benefits. Scientific understanding of soil organic matter dynamics is constantly evolving, and the past decade has seen major advances and paradigm shifts. Soil organic matter creation from decaying plant litter is now thought to occur under two separate pathways, yielding two functionally different types: predominantly plant-derived, unprotected particulate organic matter (POM) and predominantly microbially-derived, mineral-associated organic matter (MAOM). The idea of naturally-occurring humic substances in soils has been largely abandoned, and long-term soil organic matter persistence is now understood to be driven mainly by mineral association. We will present the research behind these paradigm shifts, and show how considering POM and MAOM separately is key to understanding the mechanisms driving carbon accrual and persistence in soil, and therefore to guiding policy and management for soil carbon sequestration. We will present drivers of POM and MAOM contents, from individual fields to continents, including their capacity for sequestration and saturation in agricultural soils of the USA, and their responses to common management practices in agroecosystems.

DIFFERENTIATION AND COMPLEXITY IN AGROECOSYSTEMS OF THE MEXICAN SUB-HUMID TROPICS

<p><strong>Background.</strong> In Mexico, the transition from a welfare state to a minimal state in the eighties generated a change in public policies that affected the poorest farmers in the country. <strong>Objective.</strong> This study analyzes the transformation of agroecosystem management practices in an area of the Mexican sub-humid tropics as a result of government abandonment of this productive sector. <strong>Methodology.</strong> This research is qualitative and requires techniques such as in-depth interviews and fieldwork. Thirty-seven (37) interviews were conducted with farmers over 60 years old. Participants were identified based on an intentional sample using the "snowball" technique. These findings are theoretically interpreted through Luhmann's complexity paradox. <strong>Results.</strong> The change in public policies, as well as the reduction in public spending assigned to the agricultural sector, led to changes in the management practices of agroecosystems, especially among producers with fewer resources that led to a process of differentiation between them and, at the same time, the existence of multiple interdependencies between them, as a way of dealing with the complexity derived from the conditions imposed by the predominance of a market economy, the abandonment of the government and, in recent years, the uncertainty in the behavior of the main agroclimatic variables. <strong>Implications.</strong> This work is qualitative and carried out in a local context but provides highlights on changes in areas relatively similar to the study area.<strong> Conclusion.</strong> The process of differentiation and interdependence among agroecosystems is based on the use of various technical-productive strategies, in addition to the use of collective work and social trust as social resources that help producers with fewer resources to deal with a complex problem.</p>

The management type used in plum orchards alters the functional community structure of arthropod predators

The management practices in agroecosystems can alter the community structure of pests’ natural enemies, which can consequently disturb their biocontrol function. Here, we investigated how organic or conventional farming influence the community structure of arthropod predators (spiders, coccinelids, anthocorids, ants) in orchards. The three conventional orchards studied were plum tree monocultures where mainly fungicides were applied. The three organic orchards studied were dominated by plum trees with admixture of apple trees and no agrochemical was applied. We found that management significantly affected only spiders that were less abundant in the conventional orchards than in the organic orchards. In addition, the conventional management resulted in reduced species density and altered the community composition of spiders. The conventional management reduced the functional dispersion of spider body size, which may narrow the size-spectrum of pests that could be reduced by spiders. The conventional management also reduced abundances of foliage hunters and space-web spiders. Since these spiders are effective against various insect pests, the conventional management of applying fungicides might result in increased crop damage via increased insect pests.

Agroecosystem Management Practices on some Cucumber Plant Parameters using Integrated Fertilization under Green House

This study was conducted in Tainal watershed, Bazian City, west of Sulaimaniyah, north of Iraq (35º57’31’’N, 45º 17’98’’E), the soil fertility was analyzed before the application of kinds of soil biofertilizer like dry yeast Saccharomyces cerevisiae with two concentrations (5g-L, 10 g-L) of dry yeast. Biofertilizers, organic matter like humic acid and chemical fertilizer for more comparison and water as a control. Results using dry yeast (10 g-L) have significant differences in (P?0.05) on the vegetable parameters, plant height, leaf area, yield, the number of harvest day and the weight of root system. Also the humic acid and biofertilizers have a significant effect (P?0.05). The yeast (10 g/L) have significant differences on (P?0.05) on yield (1.3 ton/ha) comparing with control of 48.73 kg/5 m2, and the total leaf area of 1.5 m2 comparing with the control 1.16 m2. The experiment was performed as factorial with randomized completely block design (R.C.B.D) on Cucumber plant type of (SAIF F1) with three replicates; each unit from the 18 unite (plot) contained 18 cucumber plant. The data were analyzed by using XLSTAT program statistically analyst.

Agroecosystem Management Practices on some Cucumber Plant Parameters using Integrated Fertilization under Green House

Agroecosystem Management Practices on some Cucumber Plant Parameters using Integrated Fertilization under Green House

Response of soil microbes to a reduction in phosphorus fertilizer in rice-wheat rotation paddy soils with varying soil P levels

Reducing chemical fertilization is one of the best management practices in agro-ecosystems where soil phosphorus (P) has accumulated to excessive levels. However, few studies have focused on the response of soil microbes to decreases in P input in a rice-wheat rotation. To determine the feasibility of a P reduction regime and its impacts on soil microbes, we modified P fertilizer inputs in a four-year pot experiment. Our treatments contained P fertilization during both rice and wheat seasons (PR + W), P fertilization during wheat-growing season only (PW), P fertilization during the rice season only (PR), and no P fertilization during either rice or wheat season (Pzero) as the control. We used ten paddy soils with varied P levels, including P-rich, P-moderate, and P-low. After four years of rice-wheat cropping, the PW treatment maintained crop yields but reduced soil Olsen-P accumulation by 20.8–88.7% (p < 0.05) compared to current farming practices (PR + W); however, the PR and Pzero treatments significantly decreased wheat yield (p < 0.05). The critical levels of soil Olsen-P were 4.19–5.24 and 7.00–16.8 mg kg−1 for optimal rice and wheat yield, respectively. Analysis of 454 pyrosequencing data from fresh samples revealed that the fertilizer regime was the main factor impacting the soil microbiome, followed by soil properties and available P. Subsequent stepwise regression analysis further indicated that soil pH was a major driver of bacterial community composition. Furthermore, the relative abundances of Alphaproteobacteria and Gammaproteobacteria were higher in P-fertilized soils. There were no significant changes in the taxonomic composition of the nine dominant bacteria phyla between the PW and PR + W treatments in soils form Yixing city, suggesting that this P fertilization reduction regime did not alter the bacterial community composition in this region. The results could help to understand the effects of P fertilizer reduction on the soil microbial community in rice-wheat rotation paddy soils.

Identifying critical thresholds to guide management practices in agro-ecosystems: Insights from bird community response to an open grassland-to-forest gradient

Landscapes are showing increased fragmentation and habitat loss due to land-use conversion and intensification, leading to species-poor and homogeneous communities. The identification of ecological thresholds above which major changes in community composition take place, may prevent the critical downfall of biodiversity while improving the effectiveness of conservation, resource management and restoration practices. In this study, we provide a new insight on how species distribute along a highly variegated agro-ecosystem in the Mediterranean region. We aim to define the thresholds of occurrence of a bird community inhabiting a tree canopy gradient, and determine the patterns of community change. We fit Huisman-Olff-Fresco models to bird occurrence data (assuming non-linear responses) to identify species-specific responses to the gradient, species richness, and turnover patterns. The tree canopy gradient is responsible for major changes in bird community likely related to the variation of the tree stratum and canopy enclosure which reflect different niche segregation opportunities. Maximum species richness was reached at 10% canopy cover while total turnover rate was higher than expected from a null model up to 10% canopy cover. Ecological thresholds can be used as indicators of specific resource limits responsible for changes in community composition and species occurrence, identifying where populations may be more sensitive. Choosing a single management scheme will invariably result in winners and losers, but optimal levels of management can be explored in order to maximize species diversity across Mediterranean agro-ecosystems.

Bacterial mobilization and transport through manure enriched soils: Experiment and modeling

A precise evaluation of bacteria transport and mathematical investigations are useful for best management practices in agroecosystems. In this study, using laboratory experiments and modeling approaches, we assess the transport of bacteria released from three types of manure (cow, sheep, and poultry) to find the importance of the common manures in agricultural activities in soil and water pollution. Thirty six intact soil columns with different textures (sandy, loamy, and silty clay loam) were sampled. Fecal coliform leaching from layers of the manures on the soil surface was conducted under steady-state saturated flow conditions at 20 °C for up to four Pore Volumes (PVs). Separate leaching experiments were conducted to obtain the initial concentrations of bacteria released from the manures (Co). Influent (Co) and effluent (C) bacteria concentrations were measured by the plate-count method and the normalized concentrations (C/C0) were plotted versus PV representing the breakthrough curves (BTCs). Transport parameters were predicted using the attachment/detachment model (two-kinetic site) in HYDRUS-1D. Simulations fitted well the experimental data (R2 = 0.50–0.96). The attachment, detachment, and straining coefficients of bacteria were more influenced by the soils treated with cow manure compared to the sheep and poultry manures. Influent curves of fecal coliforms from the manures (leached without soil) illustrated that the poultry manure had the highest potential to pollute the effluent water from the soils in term of concentration, but the BTCs and simulated data related to the treated soils illustrated that the physical shape of cow manure was more important to both straining and detachment of bacteria back into the soil solution. Detachment trends of bacteria were observed through loam and silty clay loam soils treated with cow manure compared to the cow manure enriched sandy soil. We conclude that management strategies must specifically minimize the effect of fecal coliform concentrations before field application, especially for the combination of poultry and cow manures, which has higher solubility and tailing behavior, respectively. Interestingly, the addition of sheep manure with all three soils had the lowest mobilization of bacteria. We also suggest studying the chemistry of soil solution affected by manures to present all relevant information which affect bacterial movement through soils during leaching.

Soil quality index of a crosby silt loam in central Ohio

• We assessed soil quality index using the scoring function analysis. • The saturated hydraulic conductivity was the key soil physical indicator for SQI. • The soil organic carbon was the key soil chemical indicator for SQI. • The SQI was significantly correlated with corn yield. Soil quality index (SQI) assessment is an important tool for evaluating land use and soil management practices in agroecosystems. Thus, the objectives of this research were to assess SQI using the scoring function analysis for different agricultural management practices, and to evaluate the effects of tillage and drainage systems on SQI of a crosby silt loam in central Ohio. Treatments included two tillage: no-till (NT), chisel tillage (CT), and two drainage factors: drainage ( D ) and no-drainage (ND). Three main steps were followed for the SQI assessment: (1) identification of the minimum data set of indicators, (2) indicator interpretation, and (3) integration of all indicator scores into one SQI value. The data showed that saturated hydraulic conductivity ( K sat ) and soil organic carbon (SOC) concentration were the most discriminating and key indicator for SQI assessment. The SQI was not significantly affected by subsurface drainage treatment ( D = 0.69 and ND = 0.70, P = 0.763). The results imply that long-term NT and subsurface drainage may not significantly alter the SQI because of the effects of weather condition, crop rotation, and weed-control. The SQI was significantly correlated with corn yield ( R = 0.62, P < 0.05; n = 12), suggesting that the SQI is an effective and useful tool for assessing the agronomic productivity. The SQI computed by the method described is a useful tool to synthesize the soil and agronomic information.

Net Global Warming Potential and Greenhouse Gas Intensity Influenced by Irrigation, Tillage, Crop Rotation, and Nitrogen Fertilization

Little information exists about how global warming potential (GWP) is affected by management practices in agroecosystems. We evaluated the effects of irrigation, tillage, crop rotation, and N fertilization on net GWP and greenhouse gas intensity (GHGI or GWP per unit crop yield) calculated by soil respiration (GWP and GHGI) and organic C (SOC) (GWP and GHGI) methods after accounting for CO emissions from all sources (irrigation, farm operations, N fertilization, and greenhouse gas [GHG] fluxes) and sinks (crop residue and SOC) in a Lihen sandy loam from 2008 to 2011 in western North Dakota. Treatments were two irrigation practices (irrigated vs. nonirrigated) and five cropping systems (conventional-till malt barley [ L.] with N fertilizer [CTBN], conventional-till malt barley with no N fertilizer [CTBO], no-till malt barley-pea [ L.] with N fertilizer [NTB-P], no-till malt barley with N fertilizer, and no-till malt barley with no N fertilizer [NTBO]). While CO equivalents were greater with irrigation, tillage, and N fertilization than without, NO and CH fluxes were 2 to 218 kg CO eq. ha greater in nonirrigated NTBN and irrigated CTBN than in other treatments. Previous year's crop residue and C sequestration rate were 202 to 9316 kg CO eq. ha greater in irrigated NTB-P than in other treatments. Compared with other treatments, GWP and GWP were 160 to 9052 kg CO eq. ha lower in irrigated and nonirrigated NTB-P. Similarly, GHGI and GHGI were lower in nonirrigated NTB-P than in other treatments. Regardless of irrigation practices, NTB-P may lower net GHG emissions more than other treatments in the northern Great Plains.

A 1915–2011 microscale record of soil organic matter under wheat cultivation using FTIR-PAS depth-profiling

Soil organic matter (SOM) is a keystone soil property that influences soil biological, chemical, and physical properties important for soil health. Due to the high fraction of carbon within SOM, soil organic C is an important and readily manageable component of the global carbon cycle. Agroecosystem management practices strongly influence SOM content and structural chemistry. However, there are few sites where long-term effects, e.g., more than 100 years, of agroecosystem management on SOM can be studied. We hypothesized that long-term wheat production and changes in residue management would alter SOM structural chemistry through time and space. Here, soil samples from years 1915, 1938, 1962, 1988, and 2011 were acquired from the continuous wheat with inorganic fertilizer application plot (plot 2) established in the year 1888 at Sanborn Field, Columbia, Missouri, USA. Control soil samples were collected in the year 2011 from a nearby native prairie. SOM structure was analyzed as a function of distance from the particle surface, at the micrometer scale, by Fourier transform infrared photoacoustic spectroscopy (FTIR-PAS). Our results show that SOM profiles are very heterogeneous, but three different layers were identifiable in spectra collected using FTIR-PAS depth-profiling as follows: (1) a surface layer, ranging 0–20 μm, that exhibits enrichment of C–O bonds, (2) a middle layer, ranging 20–40 μm, displaying an abundance of aromatic C = C bonds, and (3) an inner layer, ranging 40–100 μm, containing more heterocyclic N moieties. Our findings show that transformation of SOM was accelerated during the first 50 years of wheat cropping and fertilization, especially in the surface layer. However, further changes in SOM structure were remarkably retarded between 1962 and 2011 due to a change in cropping practice that retained crop residue on the plot.

A meta-analysis of the effects of pesticides and fertilizers on survival and growth of amphibians

The input of agrochemicals has contributed to alteration of community composition in managed and associated natural systems, including amphibian biodiversity. Pesticides and fertilizers negatively affect many amphibian species and can cause mortality and sublethal effects, such as reduced growth and increased susceptibility to disease. However, the effect of pesticides and fertilizers varies among amphibian species. We used meta-analytic techniques to quantify the lethal and sublethal effects of pesticides and fertilizers on amphibians in an effort to review the published work to date and produce generalized conclusions. We found that pesticides and fertilizers had a negative effect on survival of −0.9027 and growth of −0.0737 across all reported amphibian species. We also observed differences between chemical classes in their impact on amphibians: inorganic fertilizers, organophosphates, chloropyridinyl, phosphonoglycines, carbamates, and triazines negatively affected amphibian survival, while organophosphates and phosphonoglycines negatively affected amphibian growth. Our results suggest that pesticides and fertilizers are an important stressor for amphibians in agriculturally dominated systems. Furthermore, certain chemical classes are more likely to harm amphibians. Best management practices in agroecosystems should incorporate amphibian species-specific response to agrochemicals as well as life stage dependent susceptibility to best conserve amphibian biodiversity in these landscapes.

Effects of organic and inorganic fertilization on soil bacterial and fungal microbial diversity in the Kabete long-term trial, Kenya

The effects of crop manure and inorganic fertilizers on composition of microbial communities of central high land soils of Kenya are poorly known. For this reason, we have carried out a thirty-two-year-old long-term trial in Kabete, Kenya. These soils were treated with organic (maize stover (MS) at 10 t ha−1, farmyard manure (FYM) at 10 t ha−1) and inorganic fertilizers 120 kg N, 52.8 kg P (N2P2), N2P2 + MS, N2P2 + FYM, a control, and a fallow for over 30 years. We examined 16S rRNA gene and 28S rRNA gene fingerprints of bacterial and fungal diversity by PCR amplification and denaturing gradient gel electrophoresis separation, respectively. The PCR bacterial community structure and diversity were negatively affected by N2P2 and were more closely related to the bacterial structure in the soils without any addition (control) than that of soils with a combination of inorganic and organic or inorganic fertilizers alone. The effect on fungal diversity by N2P2 was different than the effect on bacterial diversity since the fungal diversity was similar to that of the N2P2 + FYM and N2P2 + MS-treated. However, soils treated with organic inputs clustered away from soils amended with inorganic inputs. Organic inputs had a positive effect on both bacterial and fungal diversity with or without chemical fertilizers. Results from this study suggested that total diversity of bacterial and fungal communities was closely related to agro-ecosystem management practices and may partially explain the yield differences observed between the different treatments.