Leaching of antibiotic resistance genes and microbial assemblages following poultry litter applications in karst and non-karst landscapes.

Antibiotic resistance is increasingly recognized as a critical challenge affecting human, animal, and environmental health. Yet, environmental dynamics and transport of antibiotic resistance genes (ARGs) and microbial communities in karst and non-karst leachate following poultry litter land applications are not well understood. This study investigates impacts of broiler poultry litter application on the proliferation of ARGs (tetW, qnrS, ermB, sulI, and blaCTX-M-32), class 1 integron (intI1 i), and alterations in microbial communities (16S rRNA) within karst derived soils, which are crucial and under-researched systems in the global hydrological cycle, and non-karst landscapes. Using large, intact soil columns (45 cm diam. × 100 cm depth) from karst and non-karst landscapes, the role of preferential flow and ARG transport in leachate was enumerated following surface application of poultry litter and simulated rain events. This research demonstrated that in poultry litter amended karst soils, ARG (i.e., ermB and tetW) abundance in leachate increased 1.5 times compared to non-karst systems (p < 0.05), highlighting the influence of geological factors on ARG proliferation. Notably, microbial communities in karst soil leachate exhibited increased diversity and abundance, suggesting a potential linkage between microbial composition and ARG presence. Further, our correlation and network analyses identified relationships between leachate ARGs, microbial taxa, and physicochemical properties, underscoring the complex interplay in these environmentally sensitive areas. These findings illuminate the critical role of karst systems in shaping ARG abundance and pollutant dispersal and microbial community dynamics, thus emphasizing the need for landscape-specific approaches in managing ARG dissemination to the environment. This study provides a deeper understanding of hydrogeological ARG dynamics but also lays the groundwork for future research and strategies to mitigate ARG dissemination through targeted manure applications across agricultural landscapes.

Heavy metals concentration in soils across the conterminous USA: Spatial prediction, model uncertainty, and influencing factors.

Assessment and proper management of sites contaminated with heavy metals require precise information on the spatial distribution of these metals. This study aimed to predict and map the distribution of Cd, Cu, Ni, Pb, and Zn across the conterminous USA using point observations, environmental variables, and Histogram-based Gradient Boosting (HGB) modeling. Over 9180 surficial soil observations from the Soil Geochemistry Spatial Database (SGSD) (n = 1150), the Geochemical and Mineralogical Survey of Soils (GMSS) (n = 4857), and the Holmgren Dataset (HD) (n = 3400), and 28 covariates (100 m × 100 m grid) representing climate, topography, vegetation, soils, and anthropic activity were compiled. Model performance was evaluated on 20 % of the data not used in calibration using the coefficient of determination (R2), concordance correlation coefficient (ρc), and root mean square error (RMSE) indices. Uncertainty of predictions was calculated as the difference between the estimated 95 and 5 % quantiles provided by HGB. The model explained up to 50 % of the variance in the data with RMSE ranging between 0.16 (mg kg-1) for Cu and 23.4 (mg kg-1) for Zn, respectively. Likewise, ρc ranged between 0.55 (Cu) and 0.68 (Zn), respectively, and Zn had the highest R2 (0.50) among all predictions. We observed high Pb concentrations near urban areas. Peak concentrations of all studied metals were found in the Lower Mississippi River Valley. Cu, Ni, and Zn concentrations were higher on the West Coast; Cd concentrations were higher in the central USA. Clay, pH, potential evapotranspiration, temperature, and precipitation were among the model's top five important covariates for spatial predictions of heavy metals. The combined use of point observations and environmental covariates coupled with machine learning provided a reliable prediction of heavy metals distribution in the soils of the conterminous USA. The updated maps could support environmental assessments, monitoring, and decision-making with this methodology applicable to other soil databases, worldwide.

Dynamic geospatial modeling of mycotoxin contamination of corn in Illinois: unveiling critical factors and predictive insights with machine learning.

Mycotoxin contamination of corn is a pervasive problem that negatively impacts human and animal health and causes economic losses to the agricultural industry worldwide. Historical aflatoxin (AFL) and fumonisin (FUM) mycotoxin contamination data of corn, daily weather data, satellite data, dynamic geospatial soil properties, and land usage parameters were modeled to identify factors significantly contributing to the outbreaks of mycotoxin contamination of corn grown in Illinois (IL), AFL >20 ppb, and FUM >5 ppm. Two methods were used: a gradient boosting machine (GBM) and a neural network (NN). Both the GBM and NN models were dynamic at a state-county geospatial level because they used GPS coordinates of the counties linked to soil properties. GBM identified temperature and precipitation prior to sowing as significant influential factors contributing to high AFL and FUM contamination. AFL-GBM showed that a higher aflatoxin risk index (ARI) in January, March, July, and November led to higher AFL contamination in the southern regions of IL. Higher values of corn-specific normalized difference vegetation index (NDVI) in July led to lower AFL contamination in Central and Southern IL, while higher wheat-specific NDVI values in February led to higher AFL. FUM-GBM showed that temperature in July and October, precipitation in February, and NDVI values in March are positively correlated with high contamination throughout IL. Furthermore, the dynamic geospatial models showed that soil characteristics were correlated with AFL and FUM contamination. Greater calcium carbonate content in soil was negatively correlated with AFL contamination, which was noticeable in Southern IL. Greater soil moisture and available water-holding capacity throughout Southern IL were positively correlated with high FUM contamination. The higher clay percentage in the northeastern areas of IL negatively correlated with FUM contamination. NN models showed high class-specific performance for 1-year predictive validation for AFL (73%) and FUM (85%), highlighting their accuracy for annual mycotoxin prediction. Our models revealed that soil, NDVI, year-specific weekly average precipitation, and temperature were the most important factors that correlated with mycotoxin contamination. These findings serve as reliable guidelines for future modeling efforts to identify novel data inputs for the prediction of AFL and FUM outbreaks and potential farm-level management practices.

Long-term impacts of conservation pasture management in manuresheds on system-level microbiome and antibiotic resistance genes.

Animal manure improves soil fertility and organic carbon, but long-term deposition may contribute to antibiotic resistance genes (ARGs) entering the soil-water environment. Additionally, long-term impacts of applying animal manure to soil on the soil-water microbiome, a crucial factor in soil health and fertility, are not well understood. The aim of this study is to assess: (1) impacts of long-term conservation practices on the distribution of ARGs and microbial dynamics in soil, and runoff; and (2) associations between bacterial taxa, heavy metals, soil health indicators, and ARGs in manures, soils, and surface runoff in a study following 15 years of continuous management. This management strategy consists of two conventional and three conservation systems, all receiving annual poultry litter. High throughput sequencing of the 16S ribosomal RNA was carried out on samples of cattle manure, poultry litter, soil, and runoff collected from each manureshed. In addition, four representative ARGs (intl1, sul1, ermB, and blactx-m-32) were quantified from manures, soil, and runoff using quantitative PCR. Results revealed that conventional practice increased soil ARGs, and microbial diversity compared to conservation systems. Further, ARGs were strongly correlated with each other in cattle manure and soil, but not in runoff. After 15-years of conservation practices, relationships existed between heavy metals and ARGs. In the soil, Cu, Fe and Mn were positively linked to intl1, sul1, and ermB, but trends varied in runoff. These findings were further supported by network analyses that indicated complex co-occurrence patterns between bacteria taxa, ARGs, and physicochemical parameters. Overall, this study provides system-level linkages of microbial communities, ARGs, and physicochemical conditions based on long-term conservation practices at the soil-water-animal nexus.

Gradient boosting machine learning model to predict aflatoxins in Iowa corn.

Introduction: Aflatoxin (AFL), a secondary metabolite produced from filamentous fungi, contaminates corn, posing significant health and safety hazards for humans and livestock through toxigenic and carcinogenic effects. Corn is widely used as an essential commodity for food, feed, fuel, and export markets; therefore, AFL mitigation is necessary to ensure food and feed safety within the United States (US) and elsewhere in the world. In this case study, an Iowa-centric model was developed to predict AFL contamination using historical corn contamination, meteorological, satellite, and soil property data in the largest corn-producing state in the US. Methods: We evaluated the performance of AFL prediction with gradient boosting machine (GBM) learning and feature engineering in Iowa corn for two AFL risk thresholds for high contamination events: 20-ppb and 5-ppb. A 90%-10% training-to-testing ratio was utilized in 2010, 2011, 2012, and 2021 (n = 630), with independent validation using the year 2020 (n = 376). Results: The GBM model had an overall accuracy of 96.77% for AFL with a balanced accuracy of 50.00% for a 20-ppb risk threshold, whereas GBM had an overall accuracy of 90.32% with a balanced accuracy of 64.88% for a 5-ppb threshold. The GBM model had a low power to detect high AFL contamination events, resulting in a low sensitivity rate. Analyses for AFL showed satellite-acquired vegetative index during August significantly improved the prediction of corn contamination at the end of the growing season for both risk thresholds. Prediction of high AFL contamination levels was linked to aflatoxin risk indices (ARI) in May. However, ARI in July was an influential factor for the 5-ppb threshold but not for the 20-ppb threshold. Similarly, latitude was an influential factor for the 20-ppb threshold but not the 5-ppb threshold. Furthermore, soil-saturated hydraulic conductivity (Ksat) influenced both risk thresholds. Discussion: Developing these AFL prediction models is practical and implementable in commodity grain handling environments to achieve the goal of preventative rather than reactive mitigations. Finding predictors that influence AFL risk annually is an important cost-effective risk tool and, therefore, is a high priority to ensure hazard management and optimal grain utilization to maximize the utility of the nation's corn crop.

Combined Dusp4 and p53 loss with Dbf4 amplification drives tumorigenesis via cell cycle restriction and replication stress escape in breast cancer.

AIM: Deregulated signaling pathways are a hallmark feature of oncogenesis and driver of tumor progression. Dual specificity protein phosphatase 4 (DUSP4) is a critical negative regulator of the mitogen-activated protein kinase (MAPK) pathway and is often deleted or epigenetically silenced in tumors. DUSP4 alterations lead to hyperactivation of MAPK signaling in many cancers, including breast cancer, which often harbor mutations in cell cycle checkpoint genes, particularly in TP53. METHODS: Using a genetically engineered mouse model, we generated mammary-specific Dusp4-deleted primary epithelial cells to investigate the necessary conditions in which DUSP4 loss may drive breast cancer oncogenesis. RESULTS: We found that Dusp4 loss alone is insufficient in mediating tumorigenesis, but alternatively converges with loss in Trp53 and MYC amplification to induce tumorigenesis primarily through chromosome 5 amplification, which specifically upregulates Dbf4, a cell cycle gene that promotes cellular replication by mediating cell cycle checkpoint escape. CONCLUSIONS: This study identifies a novel mechanism for breast tumorigenesis implicating Dusp4 loss and p53 mutations in cellular acquisition of Dbf4 upregulation as a driver of cellular replication and cell cycle checkpoint escape.

Spatial monitoring technologies for coupling the soil plant water animal nexus.

Systems-level studies aimed at determining how soil properties are linked to plant production and ultimately animal response spatially are lacking. This study aims to identify if grazing pressure is linked to soil properties, terrain attributes, and above-ground plant accumulation and nutritive value in a silvopastoral (or integrated tree-livestock) system. Overall, cattle prefer grazing native grasses (2.81 vs. 1.24 h ha-1 AU-1) and udic (dry) landscape positions compared to aquic (wet) areas (2.07 vs. 1.60 h ha-1 AU-1). Greater grazing frequency occurs in udic soils with greater phosphorus and potassium contents and with accumulated forage with less lignin (P ≤ 0.05), which correspond to reduced elevation and greater tree height and diameter (shade) during summer mob grazing. Combining spatial monitoring technologies (both soil and animal) with forage allowance can optimize grazing systems management and sustainability spatially and temporally.

Platelet olfactory receptor activation limits platelet reactivity and growth of aortic aneurysms.

As blood transitions from steady laminar flow (S-flow) in healthy arteries to disturbed flow (D-flow) in aneurysmal arteries, platelets are subjected to external forces. Biomechanical platelet activation is incompletely understood and is a potential mechanism behind antiplatelet medication resistance. Although it has been demonstrated that antiplatelet drugs suppress the growth of abdominal aortic aneurysms (AAA) in patients, we found that a certain degree of platelet reactivity persisted in spite of aspirin therapy, urging us to consider additional antiplatelet therapeutic targets. Transcriptomic profiling of platelets from patients with AAA revealed upregulation of a signal transduction pathway common to olfactory receptors, and this was explored as a mediator of AAA progression. Healthy platelets subjected to D-flow ex vivo, platelets from patients with AAA, and platelets in murine models of AAA demonstrated increased membrane olfactory receptor 2L13 (OR2L13) expression. A drug screen identified a molecule activating platelet OR2L13, which limited both biochemical and biomechanical platelet activation as well as AAA growth. This observation was further supported by selective deletion of the OR2L13 ortholog in a murine model of AAA that accelerated aortic aneurysm growth and rupture. These studies revealed that olfactory receptors regulate platelet activation in AAA and aneurysmal progression through platelet-derived mediators of aortic remodeling.

Do Long-Term Conservation Pasture Management Practices Influence Microbial Diversity and Antimicrobial Resistant Genes in Runoff?

Runoff from land-applied manure and poultry litter is one mechanism by which manure-borne bacteria are transported over large distances in the environment. There is a global concern that antimicrobial resistant (AMR) genes may be transmitted through the food chain from animal manures to soil to surface water. However, details are lacking on the ecology of AMR genes in water runoff as well as how conservation management practices may affect the runoff microbiome or minimize the movement of AMR genes. The aim of this study was to identify microbial community structure and diversity in water runoff following 14-years of poultry litter and cattle manure deposition and to evaluate the amount of AMR genes under five conventional and conservation pasture management strategies. Since 2004, all watersheds received annual poultry litter at a rate of 5.6 Mg ha-1 and were consistently managed. Surface runoff samples were collected from each watershed from 2018 to 2019, characterized using Illumina 16S rRNA gene amplicon sequencing and enumerated for four AMR-associated genes (ermB, sulI, intlI, and blactx-m-32 ) using quantitative PCR. Overall, long-term pasture management influenced water microbial community structure, with effects differing by year (p < 0.05). Bacterial richness (Chao1 index) was influenced by pasture management, with the lowest richness occurring in the control (nearby non-agricultural water source) and the greatest under fields that were hayed (no cattle presence). Runoff bacterial richness in watersheds increased following poultry litter applications, indicating poultry litter is a possible source of bacteria and altered runoff community structure. The blactx-m-32 gene was not detected in any surface water sample. The remaining three AMR genes were absent in the non-agricultural control, but present in agricultural samples. However, there was no impact (p > 0.05) from pasture management on the abundance of these genes, indicating both conventional and conservation practices have similar ecologies for these targets; however, there was a greater detection of sulI genes from runoff in continuously grazed systems in 2019, with hay being lowest in 2019. Results illustrate that the edge of field buffer strips may increase bacterial richness in water runoff, but these changes in richness do not greatly impact target AMR genes in the United States largest land-use category.

Conservation management practices reduce non-point source pollution from grazed pastures.

Producers in Northwest Arkansas and globally need alternative management practices to ensure long-term sustainable and economical use of poultry litter, which is an abundant source of valuable carbon (C), nitrogen (N) and phosphorus (P). Project objectives were to measure the efficacy of conservation management practices (i.e., pasture aeration and subsurface litter incorporation) to reduce nutrient runoff compared to poultry litter surface applications from small watersheds under rainfed and grazed conditions. Watersheds (0.23 ha each) were assigned a treatment [pasture aeration, subsurface litter incorporation, or surface application of litter (positive control)] on a Leadvale (fine-silty, siliceous, thermic Typic Fragiudult) silt loam. Poultry litter was applied annually to each watershed from 2007-2012. Over the 4-yr study period, runoff loads of NO3-N, total nitrogen (TN), soluble reactive phosphorus (SRP), and total phosphorus (TP) varied per conservation practice (P ≤ 0.05). Specifically, average annual loads of NO3-N, TN, SRP, and TP loads were reduced 49, 42, 28, and 35% following pasture aeration and by 78, 72, 55, and 59% from subsurface applying poultry litter, relative to surface applications, respectively. Greatest annual N loads and runoff corresponded with surface poultry litter applications, followed by pasture aeration, with subsurface incorporation of poultry litter resulting in lowest (P ≤ 0.05) TN and NO3-N loads. Overall, subsurface incorporation of poultry litter and pasture aeration are two promising conservation practices for reducing non-point source pollution in watersheds with nutrient imbalances. Further work needs to be done on factors influencing the efficacy of these conservation practices under rainfed conditions, as well as the economic feasibility of these conservation agricultural practices.

Antimicrobial resistant gene prevalence in soils due to animal manure deposition and long-term pasture management.

The persistence of antimicrobial resistant (AMR) genes in the soil-environment is a concern, yet practices that mitigate AMR are poorly understood, especially in grasslands. Animal manures are widely deposited on grasslands, which are the largest agricultural land-use in the United States. These nutrient-rich manures may contain AMR genes. The aim of this study was to enumerate AMR genes in grassland soils following 14-years of poultry litter and cattle manure deposition and evaluate if best management practices (rotationally grazed with a riparian (RBR) area and a fenced riparian buffer strip (RBS), which excluded cattle grazing and poultry litter applications) relative to standard pasture management (continuously grazed (CG) and hayed (H)) minimize the presence and amount of AMR genes. Quantitative PCR (Q-PCR) was performed to enumerate four AMR genes (ermB, sulI, intlI, and blactx-m-32 ) in soil, cattle manure, and poultry litter environments. Six soil samples were additionally subjected to metagenomic sequencing and resistance genes were identified from assembled sequences. Following 14-years of continuous management, ermB, sulI, and intlI genes in soil were greatest (P < 0.05) in samples collected under long-term continuous grazing (relative to conservation best management practices), under suggesting overgrazing and continuous cattle manure deposition may increase AMR gene presence. In general, AMR gene prevalence increased downslope, suggesting potential lateral movement and accumulation based on landscape position. Poultry litter had lower abundance of AMR genes (ermB, sulI, and intlI) relative to cattle manure. Long-term applications of poultry litter increased the abundance of sulI and intlI genes in soil (P < 0.05). Similarly, metagenomic shotgun sequencing revealed a greater total number of AMR genes under long-term CG, while fewer AMR genes were found in H (no cattle manure) and RBS (no animal manure or poultry litter). Results indicate long-term conservation pasture management practices (e.g., RBS and RBR) and select animal manure (poultry litter inputs) may minimize the presence and abundance of AMR genes in grassland soils.

Long-term effects of grazing management and buffer strips on phosphorus runoff from pastures fertilized with poultry litter.

Phosphorus (P) runoff from pastures can cause accelerated eutrophication of surface waters. However, few long-term studies have been conducted on the effects of best management practices, such as rotational grazing and/or buffer strips on P losses from pastures. The objective of this study was to evaluate the long-term effects of grazing management and buffer strips on P runoff from pastures receiving annual (5.6 Mg ha-1 ) poultry litter applications. A 14-yr study was conducted on 15 small watersheds (0.14 ha) with five treatments: hayed (H), continuously grazed (CG), rotationally grazed (R), rotationally grazed with an unfertilized buffer strip (RB), and rotationally grazed with an unfertilized fenced riparian buffer (RBR). Runoff samples were collected using automatic samplers during runoff events. Average annual runoff volumes from H (40 mm yr-1 ) and RBR (48 mm yr-1 ) were lower than CG and RB, which were both 65 mm yr-1 , and from R (67 mm yr-1 ). Rotational grazing alone did not reduce P loads compared with continuous grazing (1.88 and 1.71 kg P ha-1 for R and CG, respectively). However, compared with CG, total P losses from RB pastures were reduced 36% with unfertilized buffer strips (1.21 kg P ha-1 ), 60% in RBR watersheds with unfertilized fenced riparian buffer strips (0.74 kg P ha-1 ), and 49% by converting pastures to hayfields (0.97 kg P ha-1 ). Hence, the use of unfertilized buffer strips, unfertilized fenced riparian buffer strips, or converting pastures to hayfields are effective best management practices for reducing P runoff in U.S. pasture systems.

Review of Antibiotic Resistance, Ecology, Dissemination, and Mitigation in U.S. Broiler Poultry Systems.

Since the onset of land application of poultry litter, transportation of microorganisms, antibiotics, and disinfectants to new locations has occurred. While some studies provide evidence that antimicrobial resistance (AMR), an evolutionary phenomenon, could be influenced by animal production systems, other research suggests AMR originates in the environment from non-anthropogenic sources. In addition, AMR impacts the effective prevention and treatment of poultry illnesses and is increasingly a threat to global public health. Therefore, there is a need to understand the dissemination of AMR genes to the environment, particularly those directly relevant to animal health using the One Health Approach. This review focuses on the potential movement of resistance genes to the soil via land application of poultry litter. Additionally, we highlight impacts of AMR on microbial ecology and explore hypotheses explaining gene movement pathways from U.S. broiler operations to the environment. Current approaches for decreasing antibiotic use in U.S. poultry operations are also described in this review.

Soil bacterial biodiversity is driven by long-term pasture management, poultry litter, and cattle manure inputs.

Soil microorganisms are important for maintaining soil health, decomposing organic matter, and recycling nutrients in pasture systems. However, the impact of long-term conservation pasture management on soil microbial communities remains unclear. Therefore, soil microbiome responses to conservation pasture management is an important component of soil health, especially in the largest agricultural land-use in the US. The aim of this study was to identify soil microbiome community differences following 13-years of pasture management (hayed (no cattle), continuously grazed, rotationally grazed with a fenced, un-grazed and unfertilized buffer strip, and a control (no poultry litter or cattle manure inputs)). Since 2004, all pastures (excluding the control) received annual poultry litter at a rate of 5.6 Mg ha-1. Soil samples were collected at a 0-15 cm depth from 2016-2017 either pre or post poultry litter applications, and bacterial communities were characterized using Illumina 16S rRNA gene amplicon sequencing. Overall, pasture management influenced soil microbial community structure, and effects were different by year (P < 0.05). Soils receiving no poultry litter or cattle manure had the lowest richness (Chao). Continuously grazed systems had greater (P < 0.05) soil community richness, which corresponded with greater soil pH and nutrients. Consequently, continuously grazed systems may increase soil diversity, owing to continuous nutrient-rich manure deposition; however, this management strategy may adversely affect aboveground plant communities and water quality. These results suggest conservation pasture management (e.g., rotationally grazed systems) may not improve microbial diversity, albeit, buffer strips were reduced nutrients and bacterial movement as evident by low diversity and fertility in these areas compared to areas with manure or poultry litter inputs. Overall, animal inputs (litter or manure) increased soil microbiome diversity and may be a mechanism for improved soil health.

A Global Perspective on Integrated Strategies to Manage Soil Phosphorus Status for Eutrophication Control without Limiting Land Productivity.

Unnecessary accumulation of phosphorus (P) in agricultural soils continues to degrade water quality and linked ecosystem services. Managing both soil loss and soil P fertility status is therefore crucial for eutrophication control, but the relative environmental benefits of these two mitigation measures, and the timescales over which they occur, remain unclear. To support policies toward reduced P loadings from agricultural soils, we examined the impact of soil conservation and lowering of soil test P (STP) in different regions with intensive farming (Europe, the United States, and Australia). Relationships between STP and soluble reactive P concentrations in land runoff suggested that eutrophication control targets would be more achievable if STP concentrations were kept at or below the current recommended threshold values for fertilizer response. Simulations using the Annual P Loss Estimator (APLE) model in three contrasting catchments predicted total P losses ranging from 0.52 to 0.88 kg ha depending on soil P buffering and erosion vulnerability. Drawing down STP in all catchment soils to the threshold optimum for productivity reduced catchment P loss by between 18 and 40%, but this would take between 30 and 40+ years. In one catchment, STP drawdown was more effective in reducing P loss than erosion control, but combining both strategies was always the most effective and more rapid than erosion control alone. By accounting for both soil P buffering interactions and erosion vulnerability, the APLE model quickly provided reliable information on the magnitude and time frame of P loss reduction that can be realistically expected from soil and STP management. Greater precision in the sampling, analysis, and interpretation of STP, and more technical innovation to lower agronomic optimum STP concentrations on farms, is needed to foster long-term sustainable management of soil P fertility in the future.

Spatial Distribution of Soil Phosphorus, Calcium, and pH after Long-term Broiler Litter Application.

Water movement over and through soil is largely driven by topography and soil management across landscapes. This research tested the hypothesis that the water movement determines the potential for P and Ca redistribution and pH variance across landscapes. This hypothesis was evaluated by using digital elevation model-derived terrain attributes in fields after 55 yr of broiler litter applications on pastures in Smith County, Mississippi. Results show that soils receiving broiler litter had mean Mehlich-3 P levels of 1221.8 mg kg at 0- to 15-cm depth and 618.6 mg kg at 15- to 30-cm depth, and Ca with mean values of 768.3 and 645.0 mg kg at 0- to 15-cm and 15- to 30-cm soil depths, respectively. Across fields, soils in areas of predicted convergent flow contained higher P, Ca, and lower pH values in the upper 0 to 15 cm, suggesting contributions via surface overland flow from areas with higher elevation and lower slope gradient. On the other hand, soils in areas with lesser slope and higher elevation also contained high levels of P, Ca, and pH for the subsurface soil depth, suggesting that vertical flow of water on this landscape is a mechanism for movement of P and Ca deeper in the profile. The incorporation of topographic characteristics across fields offers promising results that may be incorporated into improved P indices and management, making them more robust indicators of P mobilization to waterways.

Correction to: Are soils beneath coniferous tree stands more acidic than soils beneath deciduous tree stands?

Fig. 1. was amended to reduce the size of the map and improve formatting of the manuscript. The authors claim this amendment does not affect the information being conveyed.

Assessing soil organic carbon stock of Wisconsin, USA and its fate under future land use and climate change.

Carbon stored in soils contributes to a variety of soil functions, including biomass production, water storage and filtering, biodiversity maintenance, and many other ecosystem services. Understanding soil organic carbon (SOC) spatial distribution and projection of its future condition is essential for future CO2 emission estimates and management options for storing carbon. However, modeling SOC spatiotemporal dynamics is challenging due to the inherent spatial heterogeneity and data limitation. The present study developed a spatially explicit prediction model in which the spatial relationship between SOC observation and seventeen environmental variables was established using the Cubist regression tree algorithm. The model was used to compile a baseline SOC stock map for the top 30 cm soil depth in the State of Wisconsin (WI) at a 90 m × 90 m grid resolution. Temporal SOC trend was assessed by comparing baseline and future SOC stock maps based on the space-for-time substitution model. SOC prediction for future considers land use, precipitation and temperature for the year 2050 at medium (A1B) CO2 emissions scenario of the Intergovernmental Panel on Climate Change. Field soil observations were related to factors that are known to influence SOC distribution using the digital soil mapping framework. The model was validated on 25% test profiles (R2: 0.38; RMSE: 0.64; ME: -0.03) that were not used during model training that used the remaining 75% of the data (R2: 0.76; RMSE: 0.40; ME: -0.006). In addition, maps of the model error, and areal extent of Cubist prediction rules were reported. The model identified soil parent material and land use as key drivers of SOC distribution including temperature and precipitation. Among the terrain attributes, elevation, mass-balance index, mid-slope position, slope-length factor and wind effect were important. Results showed that Wisconsin soils had an average baseline SOC stock of 90 Mg ha-1 and the distribution was highly variable (CV: 64%). It was estimated that WI soils would have an additional 20 Mg ha-1 SOC by the year 2050 under changing land use and climate. Histosols and Spodosols were expected to lose 19 Mg ha-1 and 4 Mg ha-1, respectively, while Mollisols were expected to accumulate the largest SOC stock (62 Mg ha-1). All land-use types would be accumulating SOC by 2050 except for wetlands (-34 Mg C ha-1). This study found that Wisconsin soils will continue to sequester more carbon in the coming decades and most of the Driftless Area will be sequestering the greatest SOC (+63 Mg C ha-1). Most of the SOC would be lost from the Northern Lakes and Forests ecological zone (-12 Mg C ha-1). The study highlighted areas of potential C sequestration and areas under threat of C loss. The maps generated in this study would be highly useful in farm management and environmental policy decisions at different spatial levels in Wisconsin.

Are soils beneath coniferous tree stands more acidic than soils beneath deciduous tree stands?

In 2008, the Mulberry River, a National Wild and Scenic River, was listed as impaired due to low pH (below pH 6.0). Over the last 50 years, the volume of conifers in the Ozark region has increased 115% since 1978 which may result in the acidification of nearby aquatic ecosystems. The objective of this study was to determine if differences exist in soil and litter chemical properties between deciduous and coniferous tree stands. Aboveground litter (n = 200) and soil (n = 400) at 0- to 5- and 5- to 15-cm depths were collected at paired deciduous and coniferous stands at 10 locations within the Mulberry River watershed and analyzed for a suite of chemical parameters. There were no differences (P > 0.05) in several measures of soil acidity between deciduous and coniferous stands. Litter collected from the coniferous stands was more acidic than deciduous litter (4.4 vs 4.7; P < 0.05). Cation exchange capacity, exchangeable Ca and Mg, and water-soluble P and Mg contents differed (P < 0.05) by stand and depth. Cation exchange capacity and exchangeable Ca and Mg were greatest in the 0- to 5-cm depth interval of the coniferous stands. Water-soluble P and Mg contents were greatest within the 0- to 5-cm depth interval which did not differ (P > 0.05) between stand but were greater than the 5- to 15-cm depth interval. Although limited to the top 15-cm of soil, the similarity in soil acidity between stands suggests that conifer growth may not be a substantial source of acidity to the Mulberry River.

A Case Study of Environmental Benefits of Sensor-Based Nitrogen Application in Corn.

Crop canopy reflectance sensors make it possible to estimate crop N demand and apply appropriate N fertilizer rates at different locations in a field, reducing fertilizer input and associated environmental impacts while maintaining crop yield. Environmental benefits, however, have not been quantified previously. The objective of this study was to estimate the environmental impact of sensor-based N fertilization of corn using model-based environmental Life Cycle Assessment. Nitrogen rate and corn grain yield were measured during a sensor-based, variable N-rate experiment in Lincoln County, MO. Spatially explicit soil properties were derived using a predictive modeling technique based on in-field soil sampling. Soil NO emissions, volatilized NH loss, and soil NO leaching were predicted at 60 discrete field locations using the DeNitrification-DeComposition (DNDC) model. Life cycle cumulative energy consumption, global warming potential (GWP), acidification potential, and eutrophication potential were estimated using model predictions, experimental data, and life cycle data. In this experiment, variable-rate N management reduced total N fertilizer use by 11% without decreasing grain yield. Precision application of N is predicted to have reduced soil NO emissions by 10%, volatilized NH loss by 23%, and NO leaching by 16%, which in turn reduced life cycle nonrenewable energy consumption, GWP, acidification potential, and eutrophication potential by 7, 10, 22, and 16%, respectively. Although mean N losses were reduced, the variations in N losses were increased compared with conventional, uniform N application. Crop canopy sensor-based, variable-rate N fertilization was predicted to increase corn grain N use efficiency while simultaneously reducing total life-cycle energy use, GWP, acidification, and eutrophication.