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Agricultural nutrients nitrogen and phosphorus can subsequently be transported to waterways and are often managed through the adoption of best management practices (BMPs). However, we have a poor understanding of how the use of BMPs varies spatially and how BMP adoption might be related to nutrient yields in surface waters. To address this, we performed a survey of agricultural landowners across New York State and compared this with estimates of annual incremental nitrogen and phosphorus yields of agricultural origin from the Spatially Referenced Regressions On Watershed attributes (SPARROW) model. Using these socio-behavioral data and SPARROW predictions, we perform colocation analysis to identify areas where watersheds with high nutrient yield from agriculture are collocated with non-use of agricultural BMPs. This colocation analysis offers a novel methodology for identifying areas where monitoring of waterways and promotion of best management practices could be targeted to achieve the greatest benefits., (© 2024. The Author(s).)

Non-point source pollution poses a continuous threat to the quality of Great Lakes waters. To abate this problem, the Great Lakes Agricultural Stewardship Initiative (GLASI) was initiated in Ontario, Canada, with the primary aim of reducing phosphorus pollution. Therefore, a case-study analysis of the Wigle Creek watershed, one of the six priority watersheds under the GLASI program, was undertaken to evaluate the effectiveness of various existing and potential future Best Management Practices (BMPs) and to identify BMPs that might aid in mitigating the watershed's contribution to phosphorus loads reaching Lake Erie. Given the watershed's very flat topography, hydrological/nutrient modeling proved an extremely challenging exercise. The Soil and Water Assessment Tool (SWAT) model was used in this evaluation. Several digital elevation model (DEM) options were considered to accurately describe the watershed and represent flow conditions. A 30 m resolution DEM, implementing a modified burning in of streams based on ground truthing, was finally employed to develop the SWAT model's drainage framework. The model was first calibrated for flow, sediment, and phosphorus loads. The calibrated model was used to evaluate the ability of potential BMPs (minimum tillage, no-till, retiring croplands into pasture, retiring croplands into forest, winter wheat cover crop, and vegetative filter strips) to reduce phosphorus loads compared to implemented practice. Converting all croplands into pasture or forest significantly decreased P loads reaching Lake Erie. Comparatively, a winter wheat cover crop had minimal effect on reducing phosphorus loading. [ABSTRACT FROM AUTHOR]

This study was conducted in the Atwood and Tappan Lakes watersheds of the Tuscarawas basin of Ohio. The flow, total nitrogen (TN), and total phosphorus (TP) loadings were monitored with the help of local stakeholders for a few years at various locations of the watershed to develop the Soil and Water Assessment Tool (SWAT). The multi-site SWAT model calibration and validation were accomplished with a reasonable model performance. In the next step, the scenario analysis was conducted in the SWAT model using various BMPs, including vegetative filter strips, grass waterways, fertilizer reduction, crop rotation, and cover crops to evaluate their performance in reducing TN and TP from the watershed. While BMPS in many studies are decided based on researchers' intuition, these BMPs were selected based on active consultation with the local stakeholders, who were engaged in the reduction of TN and TP loadings from the watersheds. Since the SWAT model calibration for TN and TP was not as good as the hydrologic model calibration, various scenarios of TN and TP reduction using BMPs were investigated for several years using both calibrated and uncalibrated SWAT models. We examined all the BMPs in 12 sub-watersheds of the Atwood and 10 sub-watersheds of the Tappan Lake watershed. The analysis indicated that the management practices of cover crops (rye) in combination with grass waterways with a 10% fertilizer reduction could minimize the TN and TP loading by as much as 88%, without significantly compromising the agricultural yield. However, a 10% fertilizer reduction without any BMPs could reduce TN and TP by just 9%. The cover crop (rye) including 10% fertilizer reduction with grass waterways seemed to be the most effective in reducing TN and TP, whereas the implementation of a filter strip led to a 70% reduction and was the next effective BMPs in reducing TN and TP loadings. In general, TN losses were reduced by 8% to 53%, while TP losses were reduced by 7% to 88%, depending on the BMPs used. By and large, the TN and TP reduction achieved through the calibrated model was not significantly different from the uncalibrated model, even though the reduction using the calibrated model was slightly higher for all scenarios than that of the uncalibrated model. The TN and TP loadings were highly sensitive to cattle grazing. When just 50% of the cattle were permitted to graze, the model predicted that there would be a 40% increase in total nitrogen and a 70% increase in total phosphorus in both watersheds. Our investigation revealed that monitoring the watershed at a small sub-watershed scale and calibrating the SWAT model for nitrogen and phosphorus is delicate. [ABSTRACT FROM AUTHOR]

Subsurface (or tile) drainage improves land productivity by enhancing soil aeration and preventing water-logged conditions. However, the continuous expansion of drained agricultural lands and reliance on synthetic fertilizer in the Midwestern United States have increasingly facilitated nitrate transport from agricultural fields to surface water bodies. Hence, there is a need to implement various agricultural best management practices (BMPs) in order to reduce the adverse water quality impacts resulting from excess nitrate, such as eutrophication and the formation of hypoxic zones. In this study, we used a SWAT+ model to assess the overall impacts on the riverine nitrate load and crop yield in the corn–soybean cropping system based on a combination of different management practices. The corn and soybean yields simulated with the model were found to be in good agreement with the observed yields for both the calibration and validation periods. The long-term simulation over a period of 30 years showed a reduction in the nitrate load of up to 32% without impacting the crop yield. The model results suggest that by reducing the current N application rate by 20% and using a 40:60 split between spring pre-plant and side-dressing N applications combined with cereal rye as a cover crop in corn–soybean rotation, one can potentially reduce nitrate losses without impacting crop yields. This study will help researchers, stakeholders, and farmers to explore and adopt alternative management practices beneficial for offsetting the environmental impacts of agricultural productions on the watershed scale. [ABSTRACT FROM AUTHOR]

This investigation explores the impact of various management practices on nitrate leaching and crop yield in two specific areas in Slovenia. The issue of nitrate leaching from agricultural land is a worldwide threat to drinking water, and despite years of research efforts, universal solutions are still unknown. The two chosen study sites are significant because of their importance for agricultural production and because groundwater aquifers beneath are main sources of drinking water, which makes imposing mitigation measures challenging. One of the areas was reported to be of "bad" status according to the Water Framework Directive criteria, while the other is at risk of reaching this status if nitrate concentrations in groundwater continue to rise. This research used the SWAT model to simulate nitrate leaching and crop yield changes under different agricultural scenarios on different soil types. It aimed to accomplish two objectives: first, to identify parts of the case study areas where the existing combination of soil conditions and agricultural practices enables a high potential for nitrate leaching; second, to identify agricultural practices that decrease nitrate leaching from various soil types while maintaining crop yields in each area. By identifying the most vulnerable locations and the most promising practices, we generated a chart of best management practices for specific soil types as a guide that extension services can use to advise farmers on potential management improvements. The main findings demonstrate that reducing fertilizer application, both organic and inorganic, in areas where the rates exceed crop requirements may not have a significant impact on crop production. However, these reductions often resulted in a noticeable decrease in nitrate exports. The results also showed that soil type is crucially important and should always be considered when evaluating the effects of agricultural management on crop yields and nitrate leaching. [ABSTRACT FROM AUTHOR]

This investigation explores the impact of various management practices on nitrate leaching and crop yield in two specific areas in Slovenia. The issue of nitrate leaching from agricultural land is a worldwide threat to drinking water, and despite years of research efforts, universal solutions are still unknown. The two chosen study sites are significant because of their importance for agricultural production and because groundwater aquifers beneath are main sources of drinking water, which makes imposing mitigation measures challenging. One of the areas was reported to be of “bad” status according to the Water Framework Directive criteria, while the other is at risk of reaching this status if nitrate concentrations in groundwater continue to rise. This research used the SWAT model to simulate nitrate leaching and crop yield changes under different agricultural scenarios on different soil types. It aimed to accomplish two objectives: first, to identify parts of the case study areas where the existing combination of soil conditions and agricultural practices enables a high potential for nitrate leaching; second, to identify agricultural practices that decrease nitrate leaching from various soil types while maintaining crop yields in each area. By identifying the most vulnerable locations and the most promising practices, we generated a chart of best management practices for specific soil types as a guide that extension services can use to advise farmers on potential management improvements. The main findings demonstrate that reducing fertilizer application, both organic and inorganic, in areas where the rates exceed crop requirements may not have a significant impact on crop production. However, these reductions often resulted in a noticeable decrease in nitrate exports. The results also showed that soil type is crucially important and should always be considered when evaluating the effects of agricultural management on crop yields and nitrate leaching.

Reinforcing the small water cycle is considered to be a holistic approach to both water resource and landscape management. In an agricultural landscape, this can be accomplished by incorporating agricultural conservation practices; their incorporation can reduce surface runoff, increase infiltration, and increase the water holding capacity of a soil. Some typical agricultural conservation practices include: conservation tillage, contour farming, residue incorporation, and reducing field sizes; these efforts aim to keep both water and soil in the landscape. The incorporation of such practices has been extensively studied over the last 40 years. The Soil and Water Assessment Tool (SWAT) was used to model two basins in the Czech Republic (one at the farm-scale and a second at the management-scale) to determine the effects of agriculture conservation practice adoption at each scale. We found that at the farm-scale, contour farming was the most effective practice at reinforcing the small water cycle, followed by residue incorporation. At the management-scale, we found that the widespread incorporation of agricultural conservation practices significantly reinforced the small water cycle, but the relative scale and spatial distribution of their incorporation were not reflected in the SWAT scenario analysis. Individual farmers should be incentivized to adopt agricultural conservation practices, as these practices can have great effects at the farm-scale. At the management-scale, the spatial distribution of agricultural conservation practice adoption was not significant in this study, implying that managers should incentivize any adoption of such practices and that the small water cycle would be reinforced regardless.

Abstract Better management practices (BMPs) for shrimp farming are a standardized set of farming practices to ensure the environmental and financial sustainability of shrimp farming systems. Uniform implementation of the BMPs poses a challenge if most of the shrimp farms in a given region are small (<2 ha). The adoption of BMPs and the associated economics were studied in two districts of Andhra Pradesh, the state that leads India's shrimp production. The overall rate of adoption was approximately 73%. Using factor analysis, all the partly adopted BMPs were categorized into six thematic factors: optimized input supply, improved management practices, routine maintenance, social responsibility, group approach, and culture-system-related and other practices. The ordinary least square regression model explained the factors that influenced the decision to adopt a given practice. These factors included key socio-economic variables such as age, education, and membership of farmers associations. Partial budget analysis revealed that adopting all the recommended BMPs in full would decrease the net returns from each crop by 16.6%. Although adopting the BMPs is voluntary, the practices crucial to the success of a crop were adopted by all the farmers (almost as if it were mandatory to adopt them), whereas those that involved significant costs were left out. Although small farmers can be persuaded to adopt the BMPs through awareness programmes, upgrading their holdings to a size at which a standardized farming system is feasible needs substantial investment. The governments of shrimp-exporting nations should improve their regulatory structure to embrace an inclusive governance model involving all the key actors in the value chain to make the small scale shrimp farming sustainable. Highlights • Farm level adoption of Better Management Practices for sustainable shrimp farming and the associated economics were studied in detail. • Factors influencing the adoption of BMPs were found. • Institutional regulatory framework of shrimp farming was studied. [ABSTRACT FROM AUTHOR]

Benthic algae are the nutritional base of most freshwater food webs. Here we consider the nutritional contribution of benthic algae in the form of fatty acids (FAs) over multiple seasons and years. Our study was conducted in the Upper Delaware River watershed (New York, USA), where best-management practices (BMPs) had been implemented over varying numbers of years (BMP age) to mitigate effects of agricultural activities in the watershed. We defined 4 BMP categories by the presence and duration of management used in each stream drainage prior to initiating our study: 1) reference (unaffected), 2) no BMP (agriculturally affected), 3) new (agriculturally affected, BMP ≤ 2 y), and 4) old (agriculturally affected, BMP ≥ 3 y). Our results indicate that BMPs were able to reduce agricultural effects, as evidenced by a significantly lower benthic algal total FA content in reference than in agricultural streams. However, FA content did not differ between BMP-age categories, a result suggesting that BMPs were rapidly effective (within 1-2 y). Among essential molecules, amount of essential FA precursors (α-linoleic acid 18:3ω3 and linolenic acid 18:2ω6) were inversely related to their derivatives (arachidonic acid 20:4ω6, eicosapentaenoic acid 20:5ω3, docosahexaenoic acid 20:6ω3) across BMP-age categories. These outcomes suggest that BMP practices are important for maintaining the quality of the New York City metropolitan area water supply. [ABSTRACT FROM AUTHOR]

Benthic algae comprise a diversity of taxonomic lineages and produce important biochemical compounds required by higher trophic levels. Chief among these compounds are essential fatty acids (EFAs) that aquatic consumers require for their metabolic and reproductive processes. However, habitat changes from anthropogenic activities, namely, agriculture, can affect not only which species of algae may be present but also the quantity and quality of EFAs they produce. This study aims to evaluate how benthic algal taxonomic composition and EFA concentrations vary in streams affected by agriculture and remediation through stream-associated best management practices (BMPs). The study was undertaken in the Upper Delaware River watershed in New York state, in which BMPs have been installed over multiple years (= BMP age). Some results indicate that BMPs were able to reduce effects of agriculture. Changes in benthic algal assemblages, the proportions of algal taxonomic groups, and in specific taxonomic members were not significant. The proportion of diatoms in assemblages decreased with increasing agricultural effects ( F = 6.313, P = 0.001). Conversely, the proportion of chlorophytes increased in agriculturally affected streams ( F = 9.336, P < 0.001). Changes in taxonomic composition were associated with changes in various EFA compound concentrations. Agricultural streams had higher concentrations of total EFAs along with more chlorophytes ( r = −0.268, P = 0.010) and fewer diatoms ( r = 0.270, P = 0.009) than did reference or minimally affected streams. Particularly, agricultural streams had greater concentrations of key EFAs such as eicosapentaenoic acid and docosahexaenoic acid. However, there were no differences among assemblage's nutritional quality (Σω3/Σω6). The data presented here suggest that analyzing shifts in algal taxonomic groups in conjunction with measurements of fatty acids in broad EFA groups may provide more information when characterizing algal assemblages than examination of algal taxa or analysis of EFA compounds alone. [ABSTRACT FROM AUTHOR]

Phosphorus (P) losses from agricultural systems are a cause of degraded surface water quality of lakes and streams. In freshwater systems, P is often the most limiting nutrient for algae growth and an increase in P additions to these systems can cause a shift in ecology. These shifts can result in a degradation of the water resource as habitat or for recreation. In an effort to combat the negative effects of agriculture management practices on surface water quality, federal and state regulations require some level of assessment to guide P applications. Areas with large amounts of potato production are of particular concern with respect to P loss since potatoes are a high P demanding crop and are inefficient users of applied P. In many cases, soils in potato production are managed with a higher soil test P concentration compared to other crops and P applications for optimum production exceed P removal. When potato production fields are maintained at high soil test P levels, this may increase the risk of P loss in runoff. However, based on soils and landscape positions where potatoes are grown, there may be little risk of transport. While there appears to be little risk of P loss on low-sloping, sandy soils, output from the Wisconsin Phosphorus Index suggests that more steeply sloping fields can pose some risk, especially when soil test P concentrations exist at above optimum levels. At high soil test P levels, no P may be required for optimum yield in rotated crops, but production practices of these crops may need to be altered to reduce P losses. Furrow-irrigated and tile-drained fields may also pose risks of P loss to the environment. While the P demands of potato are greater than those for most crops, it is likely that most of this P will not be exported via surface runoff. Careful management considerations must be made when producing potatoes on high sloping soils, especially those close to surface water bodies. Future considerations of P management and water quality will focus on assessing leaching risk of P and this contribution to surface waters. [ABSTRACT FROM AUTHOR]

Rural communities the world over depend on agriculturally-based livelihoods. In the Canadian prairies, access to sufficient quality and quantity of water can be challenging. Agriculture is fundamentally susceptible to access to water during critical crop germination and growth periods. Climate change models for the Canadian prairies indicate, in general, that summer growing seasons will experience less frequent, but larger precipitation events. The anticipated results of a changing climate include more frequent spring flooding and a new climate regime that requires more proactive water management to ensure availability of adequate supplies at optimal times to support and sustain agricultural production. Multi-disciplinary research is investigating, quantifying, and critically assessing currently purported beneficial management practices (BMPs) for agriculture to determine rural community vulnerability and adaptability to climate change. The presentation includes research results from field scale implementation and testing of BMPs, interviews of rural communities and residents, and quantitative evaluations of rural economies, development, and adaptation strategies. [ABSTRACT FROM AUTHOR]

This article examines economic incentives and other mechanisms to offset non-point source pollution from agriculture. A biophysical simulator to estimate technical relationships is linked to linear programming models for representative farms in the Willamette Valley of Oregon. The models are then optimized for profit maximization under alternative non-point pollution control policies. The results indicate that site-specific resource conditions and production possibilities greatly influence policy effectiveness and the cost of achieving pollution abatement. Nevertheless, some abatement is possible on all farms for relatively little cost.

A process-based nitrogen model suitable for urban stormwater Best Management Practices (BMPs), when used as an extension to current stormwater models, can assist decision-making by predicting nitrogen removal performances. While such a model has not been created, process-based nitrogen modules for agricultural fields have been developed and applied. In this paper, the nitrogen modules in six agricultural models are reviewed in the perspective of assisting the development of a process-based nitrogen module for stormwater BMPs. The agricultural nitrogen modules have consistent structures and mathematical descriptions of biochemical reactions, but show more variety in incorporating environmental factors. The operational challenges, strengths, and weaknesses of simulating stormwater BMPs' nitrogen removal performances with current models are illustrated with a case study. Finally, suggestions on developing the process-based nitrogen module for stormwater BMPs are offered based on the review, the case study results, and the differences between the stormwater BMPs and agricultural fields. • Reviewed agricultural nitrogen modules from the perspective of developing process-based stormwater nitrogen modules. • Assumptions, module structures, environmental factors, and biochemical reaction kinetics were listed annd compared. • Challenges of simulating bioretention with current agricultural and stormwater models were illustrated with a case study. • Specific suggestions were offered for establishing a more mechanistically accurate nitrogen model for stormwater BMPs. [ABSTRACT FROM AUTHOR]

In this study an attempt is made to estimate nitrogen and phosphorus discharged to the environment from the striped catfish (Pangasianodon hypophthalmus) farming sector in the Mekong Delta (8°33′-10°55′N, 104°30′- 106°50′E), South Vietnam. The sector accounted for 687,000 t production in 2007 and 1,094,879 t in 2008, with over 95% of the produce destined for export to over 100 countries. Commercial and farm-made feeds are used in catfish farming, currently the former being more predominant. Nitrogen discharge levels were similar for commercial feeds (median 46.0 kg/t fish) and farm-made feeds (median 46.8 kg/t fish); whilst, phosphorus discharge levels for commercial feeds (median 14.4 kg/t fish)were considerably lower than for farm made feeds (median 18.4 kg/t fish). Based on the median nutrient discharge levels for commercial feeds, striped catfish production in the Mekong Delta discharged 31,602 t N and 9,893 t P, and 50,364 t N and 15,766 t P in 2007 and 2008, respectively. However, the amount of nutrients returned directly to the Mekong River may be substantially less than this as a significant proportion of the water used for catfish farming as well as the sludge is diverted to other agricultural farming systems. Striped catfish farming in the Mekong Delta compared favourably with other cultured species, irrespective of the type of feed used,when the total amounts of N and P discharged in the production of a tonne of production was estimated. [ABSTRACT FROM AUTHOR]

Abstract: Long-term studies of macrophyte beds growing near streams in Conesus Lake, New York, have revealed a high biomass and continuing dominance of the invasive rooted species Eurasian watermilfoil (Myriophyllum spicatum). We tested whether agricultural best management practices (BMPs) designed to reduce tributary nutrient and soil loss from the watershed could reduce populations of Eurasian watermilfoil downstream in the lake littoral. Six macrophyte beds were monitored during a 3-year baseline period (2001–2003) prior to the implementation of BMPs and for a 4-year experimental period after a variety of agricultural BMPs were implemented in three sub-watersheds. For three macrophyte beds downstream from sub-watersheds managed as part of our project, quadrat biomass decreased by 30–50% and was statistically lower than Pre-BMP baseline values in 7 of 11 experimental sample years. Biomass loss primarily in the form of the dominant Eurasian watermilfoil ranged from 6.2 to 10 t wet weight for each bed. The declines in biomass coincided with significant annual and January–August decreases in the concentrations and fluxes of dissolved nutrients, total phosphorus, and total suspended solids in nearby streams. For three macrophyte beds downstream from watersheds in which landowners applied less extensive or no new agricultural management, biomass was statistically indistinguishable from Pre-BMP baseline values in all 12 experimental sample years. Milfoil remained the overwhelmingly dominant species at all sites during the entire study period. These results provide impetus for the use of watershed nutrient management to control the nuisance growth of Eurasian watermilfoil on a local scale in the lake littoral. [Copyright &y& Elsevier]

Chesapeake Bay water quality has been a concern since 1970. In rural areas, agriculture is the dominant N and P source, and the voluntary application of best management practices (BMPs) is the primary management tool. Here we test the hypothesis that the current management approach of primarily voluntary, untargeted BMP implementation is insufficient to create detectable, widespread reductions in N, P, and total suspended solid (TSS) concentrations in agricultural watersheds of the Choptank basin, a tributary of Chesapeake Bay. To test this hypothesis, we assessed BMP implementation and sampled water quality on participating farms, at intermediate streams within each watershed, and at watershed outlets of four watersheds from 2013 to 2014. We also present water quality data from 2003 to 2014 at the outlets of 12 additional agricultural and one forested watershed and survey-directed interviews of farmers. By the end of 2014, large numbers of BMPs, both structural and cultural, had been implemented. Of the 16 agricultural watersheds, 50% showed significant decreases in baseflow N, 37.5% showed no changes, and 12.5% showed increasing TN. Baseflow P significantly decreased at just one watershed, increased at one, and remained stable at 14. Stormflow N was similar to baseflow, but stormflow P was 5 times higher than baseflow. These data partially support our hypothesis. Surveys suggested farmers considered themselves responsible for the quality of water leaving their farms, but out-of-pocket cost was the major impediment to further BMP adoption. We suggest that greater outreach and more financial support for farmers to implement BMPs is required to increase the types and densities of BMPs needed to achieve regional water quality goals. [Display omitted] • Best management practices are needed to improve Chesapeake Bay water quality. • We evaluated water quality at 3 spatial scales due to agricultural management. • Water quality improved at the outlets of 50% of the sampled watersheds. • The primary impediment to BMP adoption by farmers was out-of-pocket expense. • As of 2014, management approach inconsistently improved stream water quality. [ABSTRACT FROM AUTHOR]

In response to federal and state clean water laws, forestry best management practices (BMPs) have been developed and implemented to prevent nonpoint source water pollution. Ellefson and Miles (1985) found that estimated BMP costs in the Midwest could amount to more than half of the net returns on national forest timber sales. Henly et al. (1988) found that government costs to implement forest practice rules ranged from as little as $100,000 per year in Idaho and Nevada to more than $4 million annually in California. A review of studies in the South indicates that estimated BMP costs have increased over time. Lickwar et al. (1992) estimated Southeast average costs of $12.45 per acre, $2.34 per MBF, or 2.87% of gross stumpage values based on 1987 BMPs and prices. Woodman and Cubbage (1994) estimated Georgia average BMP costs of $24.33 per acre or $3.02 per MBF for forest industry lands and $41.65 per acre or $5.39 per MBF for NIPF lands. For Virginia, Shaffer et al. (1998) estimated median BMP costs of $18.90 per acre. These moderate cost increases could be attributed to a higher level of standards in the revision of each state BMP guidelines manual, as well as moderate price inflation. BMPs such as better road construction, water bars, culverts, and broad-based dips have been most expensive so far. To date streamside zones have not been very expensive because the rules allow most of the valuable residual tees to be harvested as long as heavy equipment does not operate near the streams. However, this limitation may become much more difficult and costly – as indicated by Kluender et al. (2000) – as fewer chainsaw fellers and cable skidders are available. Stricter BMPs, such as those already adopted to implement forest certification standards in the South or those used to protect salmon habitat in the West, could prompt more expensive southern BMPs for landowners and state agencies in the future. [ABSTRACT FROM AUTHOR]