Iron-modified biochar is a promising cost-effective material for cadmium (Cd)-contaminated soil remediation, yet how the additional iron (Fe) affects Cd uptake and translocation in rice remains unclear. This study compared two Fe-modified biochars, including impregnated biochar (I-PBC) and co-pyrolyzed biochar (Fe-PBC), with raw biochar (PBC) and explored their effects on Cd accumulation in rice under low application rates (0.1%-0.2%, w/w). These rates were selected for field applicability and cost-efficiency in regional agricultural practices. Cd-contaminated acidic soil collected from southeastern China was used in the pot experiments. In the first pot experiment, I-PBC at 0.1% significantly reduced Cd concentrations in rice grains by 26.3%, 43.7%, and 13.5%, compared with the control, PBC, and 0.1% Fe-PBC, respectively. The results from a second experiment (0.1% amendments: PBC, I-PBC, FeSO4, water-washed PBC) suggest that I-PBC enhances Cd compartmentalization in aboveground tissues by increasing Cd in the cytosolic fraction while reducing soluble Cd proportions, likely sequestering Cd into less metabolically active compartments (e.g., vesicles). Additionally, I-PBC promoted the conversion of Cd into low-toxicity Cd-oxalate complexes, as evidenced by a significant increase in the HCl-extractable Cd fraction (FHCl, predominantly Cd-oxalate) in stems. These findings demonstrate that impregnation is superior to co-pyrolysis for Fe-modified biochar in inhibiting grain Cd accumulation, with key mechanisms involving enhanced Cd chelation by oxalic acid and subcellular compartmentalization. This study highlights the potential of low-dose I-PBC for practical Cd-contaminated farmland remediation.

Edge-of-field (EoF) water sampling methods play a crucial role in understanding non-point source nutrient fate and its environmental impacts, yet accurately interpreting water quality studies, remains challenging. This study evaluates and compares four EoF runoff water sampling techniques: (1) a commercial automated sampler (ISCO) with hourly sampling, (2) a low-cost internet of things sampler low-cost sampler with hourly sampling, (3) hourly hand sampling (grab hourly sampling), and (4) intermittent grab sampling (GB) in 2023 and 2024 at a surface irrigated agricultural site in FortCollins, Colorado involving three levels of tillage intensity. Nine water quality parameters (nitrate-N, nitrite-N, total Kjeldahl nitrogen, orthophosphate-P, total phosphorus (TP), total suspended solids (TSS), total dissolved solids, pH, and specific conductivity) were measured over nine irrigation-driven and two rainfall storm runoff events. Resulting concentration values were modeled simultaneously using a Bayesian hierarchical generalized linear mixed model, enabling causal inference with uncertainty quantification while accommodating for missing data. Results show strong alignment across samplers for most analytes, confirming the validity of integrating diverse methods in long-term and widespread monitoring. However, ISCO samples exhibited consistently elevated TSS and TP due to a purge-induced sediment plume from the flume's stainless-steel bottom intake; excluding the first ISCO sample of each pair of sample draws restored agreement with other methods. These findings show the importance of flume morphology, intake placement, purge protocol, and selective data exclusion (if necessary) to ensure comparability across sampling methods.

Science-based Trials of Rowcrops Integrated with Prairie Strips (STRIPS) can improve water quality and reduce antimicrobial resistance genes (ARGs) from manured field runoff. Prior studies showed significant reductions in ARG abundances with prairie strips, but no enrichment was detected in surface soil layers, prompting further investigation into transport pathways. We hypothesized that ARGs may move vertically through strip soils. In an 8-week soil column experiment, we characterized the vertical transport of manure-amendment ARGs in prairie strip soils and leachate, comparing columns amended with anaerobically digested swine manure (ADM) and undigested swine manure (UDM) to a mineral-based control (mineral solution amendment [MIN]). In amendment manures, the ARG concentrations in ADM and UDM were similar, and ADM had increased antibiotic residual concentrations. ADM and UDM amendments resulted in elevated ARG abundances in soil and leachate compared to MIN. After manure amendment, ARGs were transported up to 52.5cm from the soil surface after rainfall events. Tetracycline resistance genes were persistently detected in amended subsurface soils, with tetM detectable until week 8 in both ADM and UDM amended soils, and tetO persisting to week 3 in ADM and week 8 in UDM amended soils. Generally, ADM amendments had lower ARG persistence than UDM, highlighting different transport dynamics depending on manure treatment. Most manure-derived ARGs appeared to be retained or degraded within the strip soil profiles, with only 9.6 and 6.1 percent of UDM and ADM amendment ARGs recovered, respectively. Our results support that prairie strips can mitigate ARGs from manured field stormwater runoff and that ARGs are transported vertically through the soils and mostly retained at surface depths.

Decision support system for agrotechnology transfer (DSSAT) provides a robust platform for evaluating long-term management effects. A CROPGRO Cotton (Gossypium hirsutum L.) model (a component of DSSAT) was calibrated using 92 data points and evaluated using 232 data points to assess its performance in simulating phenology, growth, nitrogen (N) content, seed cotton yield (SCY), and nitrogen use efficiency (NUE). The calibrated model was then used to analyze the long-term (2003-2023) effects of three planting windows (May 15-30 [planting date 1, PD1], June 1-15 [PD2], and June 15-30 [PD3]), two irrigation strategies (rainfed and rule-based irrigation), and six N rates (0, 50, 101, 151, 202, and 252kg ha-1) on SCY, NUE, and N leaching. The calibrated and evaluated model showed a good agreement between simulated and observed data. Long-term seasonal analysis indicated that median SCY in PD1 was 21% and 46% higher than in PD2 and PD3, respectively. Delayed planting reduced NUE by 37% and increased N leaching by 85%. Irrigated cotton resulted in 38% and 29% higher SCY and NUE, respectively, than rainfed cotton, without significantly increasing N leaching. NUE declined by 19%-33% with each N rate increment from 0 to 252kg N ha-1, while N leaching increased by 45% at 252kg N ha-1 compared to 0kg N ha-1. However, leaching increased significantly only when N application exceeded 151kg N ha-1. These findings emphasize the importance of adjusting N rates based on PD and irrigation strategy to maximize yield and NUE while minimizing leaching losses.

Groundwater nitrate contamination is largely attributed to fertilizer and intensive livestock manure inputs in agricultural systems. California's Salinas Valley is an area where regional policy is aimed at reducing nitrate leaching. Nonlegume winter cover crops can help decrease nitrate leaching by scavenging residual soil nitrogen (N) during winter fallow periods following the cropping season. However, the ability of fall-incorporated cover crops to decrease nitrate leaching and recycle N to subsequent cash crops is unknown. We conducted a 112-day laboratory soil incubation experiment using Merced rye (Secale cereale) cover crop shoot biomass, with four carbon-to-nitrogen (C/N) ratios (10, 14, 19, and 30), at three temperatures (10°C, 15°C, and 20°C). Destructive soil sampling was done at six intervals during the incubation to measure plant-available nitrogen. Rye biomass with the lowest C/N ratio (10) had the highest average nitrogen mineralization (Nmin) rate (56%) at the warmest temperature (20°C). Conversely, biomass with the highest C/N (30) showed net nitrogen immobilization at 10°C and 15°C during the incubation, transitioning to net mineralization only at 20°C. We found a linear correlation between soil temperature and nitrogen mineralization (at Day 112) for higher C/N ratios. Furthermore, doubling the soil mineral nitrogen content had a negligible impact on the percent mineralization of the C/N 30 residue. These results provide useful information to help farmers and policymakers understand mineralization dynamics from fall-, winter-, or spring-terminated cereal cover crops.

A new chamber-based method to measure nitrous oxide soil gas fluxes using an N2O sorbent is presented. The Greenhouse Gas Reduction through Agricultural Carbon Enhancement network (GRACEnet) protocols require grab samples (typically 25mL ea.) obtained at multiple intervals throughout chamber deployment (i.e., 0, 15, and 30min) and linear and nonlinear options to process the raw concentrations, based on goodness-of-fit tests. The new method uses a single, sorbent-stabilized large volume (400mL) gas sample collected at the end of each chamber deployment (30min) and assumes a linear concentration increase. Both methods estimate the initial (time 0) gas flux using chamber concentration changes and deployment time. This report presents a side-by-side field test in experimental plots. Samples were independently analyzed by gas chromatography and thermal desorption/gas chromatography for the standard and new method, respectively. Gas concentrations measured by both methods at the end of the chamber deployment and calculated soil gas fluxes were in close agreement (R2=0.92 and R2=0.91, respectively). Additionally, four 100mL samples taken from multiple chambers at the end of the deployment were pooled into a single cartridge to explore the sorbent's potential to further reduce the number of samples. Pooled sample results from four locations correlated well with average chamber deployments (R2=0.92 and R2=0.95 for concentrations and soil gas fluxes, respectively). These results suggest sorbent-based sampling can yield soil gas flux data of similar magnitude to interval grab sampling methods. Further testing is required to study the advantages and limitations of the new method.

Estimating black carbon (BC) emissions from biomass burning is crucial for accurately assessing the climate impact of this pollutant. In this study, we have estimated BC emissions from biomass burning in different geographic regions worldwide at a resolution of 0.25° × 0.25° from 1997 to 2023. These findings are crucial for accurately modeling the impact of BC on global climatic forcing. Over the past 27 years, the emissions of BC from global biomass burning activities have remained stable. The high BC emissions between 2003 and 2008 were associated with increased precipitation. The Southern Hemisphere South America (SHSA) and Southern Hemisphere Africa (SHAF) regions have emerged as the primary contributors, accounting for approximately 40% of total BC emissions originating from global biomass burning sources and high BC emissions in the southern hemisphere's spring. This study also reveals that BC emissions in the SHAF region during 1997-2023 exhibit a granger causal relationship with Antarctic sea ice loss at a 2-year lag, but the impact intensity demonstrates significant temporal heterogeneity. This study enhances our understanding of temporal and spatial variations in global BC release caused by biomass burning while providing fundamental data for international departments responsible for managing such activities.

Surface water monitoring of pesticides ensures adherence to environmental and human health regulatory requirements. This study focuses on an unprecedented monitoring program spanning two decades with daily or near-daily sampling across 13 states in the US Midwest and Southern United States, targeting watersheds in the upper 20th percentile of runoff vulnerability based on the United States Geological Survey watershed regressions for pesticides model. The Atrazine Ecological Monitoring Program (AEMP), mandated by the United States Environmental Protection Agency (USEPA), aims to collect extensive high-frequency atrazine exposure data alongside key environmental parameters to better understand the dynamics of atrazine fate, transport, and concentrations in these watersheds. Note, the AEMP is also referred to by the USEPA as the Atrazine Ecological Exposure Monitoring Program, or AEEMP, though the former is more commonly cited. Analysis of the 322 site-years of data revealed that sampling frequency is paramount in accurately estimating seasonal chemical concentrations and runoff loads in flowing waters. The AEMP has advanced with improved sampling techniques and a focus on increasingly vulnerable watersheds (i.e., currently representing 97th-99th centile runoff vulnerability), as evidenced by analysis of variance results indicating higher atrazine concentrations in later years, particularly post-2012. Factors such as soil conditions and precipitation were significant in influencing atrazine levels in surface water. Regression analyses underscored the interaction between agricultural activity and weather patterns as predictors of atrazine concentrations. The AEMP's detailed dataset has notably contributed to environmental risk assessment and the refinement of regulatory models. This study highlights the value of high-resolution data in vulnerable regions, emphasizing that high-frequency monitoring and inclusion of detailed environmental data significantly enhance our understanding of pesticide fate and transport in surface waters and informs stewardship efforts.