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1.
GM Crops Food ; 12(1): 106-114, 2021 Jan 02.
Artigo em Inglês | MEDLINE | ID: mdl-33079624

RESUMO

Agricultural biotechnology is enhancing agricultural productivity, food security, and livelihoods globally. Some developing countries have established functional biosafety regulatory systems and have commercialized genetically modified (GM) crops. Release of GM crops requires enhanced capacity for regulatory compliance and product stewardship to help ensure sustainable use of biotechnology products. We conducted a survey of 66 stakeholders, mostly from Africa and Asia, in two-week international agricultural biotechnology short courses. Respondents showed knowledge of biotechnology benefits and expressed potential barriers to commercialization. They identified 16 crops in the "pipeline for commercialization." Stakeholders also shared ideas about how to build capacity for product stewardship. Product stewardship is a concept which requires each person in the product life cycle - innovators, scientists, and technology users, to share responsibility. This paper focuses on adoption of product stewardship for post-release management of GM crops which encompasses trait performance, resistance management, integrated pest management (IPM), good agricultural practices, high-quality seeds and planting material, intellectual property management, labeling, identity preservation, consumer acceptance, and effective marketing.


Assuntos
Biotecnologia , Produtos Agrícolas , Agricultura , Produtos Agrícolas/genética , Abastecimento de Alimentos , Plantas Geneticamente Modificadas
2.
GM Crops Food ; 12(1): 25-35, 2021 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-32687427

RESUMO

The importance of food security and nourishment is recognized in Southern African region and in many communities, globally. However, the attainment of food security in Southern African countries is affected by many factors, including adverse environmental conditions, pests and diseases. Scientists have been insistently looking for innovative strategies to optimize crop production and combat challenges militating against attainment of food security. In agriculture, strategies of increasing crop production include but not limited to improved crop varieties, farming practices, extension services, irrigation services, mechanization, information technology, use of fertilizers and agrochemicals. Equally important is genetic modification (GM) technology, which brings new prospects in addressing food security problems. Nonetheless, since the introduction of genetically modified crops (GMOs) three decades ago, it has been a topic of public discourse across the globe, conspicuously so in Southern African region. This is regardless of the evidence that planting GMOs positively influenced farmer's incomes, economic access to food and increased tolerance of crops to various biotic and abiotic stresses. This paper looks at the issues surrounding GMOs adoption in Southern Africa and lack thereof, the discourse, and its potential in contributing to the attainment of food security for the present as well as future generations.


Assuntos
Produtos Agrícolas/genética , Alimentos Geneticamente Modificados , África Austral , Agricultura , Abastecimento de Alimentos , Plantas Geneticamente Modificadas
3.
Environ Monit Assess ; 192(11): 711, 2020 Oct 17.
Artigo em Inglês | MEDLINE | ID: mdl-33070264

RESUMO

The escalating demand for anthropic needs and urban development has highlighted the importance of monitoring and change detection of land use land cover (LULC). With an increase in agricultural expansion and infrastructural development, every land surface on earth calls for a long-term investigation of land modification patterns and their underlying contributory factors. The present investigation monitors the LULC changes and assesses the process controls in Kohima and Dimapur districts of Nagaland, India. Currently, these two districts encompassing the main urban cities of the hilly state are experiencing rapid urbanization and unplanned developmental activities. Alike any other LULC changes observed in unplanned and developing cities, these districts are likely to face environmental degradation, and particularly, the occurrence of frequent landslides and flash floods. The study has three objectives-(i) LULC mapping of Kohima and Dimapur districts for three periods (1998, 2008, and 2018), (ii) comparative analysis of LULC change patterns in the two districts during the three epochs (1998-2008, 2008-2018, and 1998-2018), and (iii) assessment of the contributory factors. For the study, remotely sensed LANDSAT images (TM and OLI) in Geographical Information System (GIS) platform were utilized along with field surveys. Supervised classification technique was employed and four major LULC classes were identified using Landsat level-1 classification system. The overall accuracy of the classification varied between 91 and 98%. Results showed that Built Up areas have increased significantly in both the districts at the rate of 322.6 ha/year in Kohima and 301.9 ha/year in Dimapur during 1998-2018. On the other hand, Agricultural Land and Forest Land declined in both districts. Changes in LULC were mainly due to marginalization of shifting cultivation, deforestation, infrastructural development, urban migration, and flourishing of aquaculture farming. This study furnishes baseline information on LULC in the data-scarce region of Northeast India and is an insinuation to the policy-makers to ensure sustainable land use planning in the face of rapid urbanization.


Assuntos
Monitoramento Ambiental , Urbanização , Agricultura , Cidades , Índia
4.
J Environ Qual ; 49(1): 97-105, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-33016356

RESUMO

Cover crops are often recommended as a best management practice to reduce erosion, weed pressure, and nutrient loss. However, cover crops may be sources of phosphorus (P) to runoff water after termination. Two greenhouse trials were conducted to determine the effects of cover crop species, termination method, and time after termination on water-extractable P (WEP) release from crop biomass. Treatments were structured in a 3 × 3 × 3 factorial and arranged in a randomized complete block design with six replicates. Treatments included three cover crop species (triticale [× Triticosecale; Triticum × Secale 'Trical'], rapeseed [Brassica napus L. 'Winfred'], and crimson clover [Trifolium incarnatum L.]); three termination methods (clipping, freezing, and herbicide); and three WEP extraction times (1, 7, and 14 d after termination). Rapeseed consistently resulted in the least WEP when exposed to the same method of termination and at the same extraction time as the other species. For both trials, terminating crop tissue via freezing increased concentrations of WEP compared with other termination methods. The WEP release from cover crop tissue increased as the time after extraction increased, but the effect was greater for herbicide- and freeze-terminated cover crops and less for clipping-terminated cover crops. Future studies on WEP release from cover crops should pay close attention to the effects of extraction timing. Producers may be able to reduce P loss from cover crop tissue by selecting cover crop species with low WEP and minimizing the amount of biomass exposed to freezing conditions.


Assuntos
Agricultura , Fósforo , Biomassa , Produtos Agrícolas , Congelamento
5.
J Environ Qual ; 49(1): 38-49, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-33016359

RESUMO

Grain producers are challenged to maximize crop production while utilizing nutrients efficiently and minimizing negative impacts on water quality. There is a particular concern about nutrient export to the Gulf of Mexico via loss from subsurface drainage systems. The objective of this study was to investigate the effects of crop rotation, tillage, crop residue removal, swine manure applications, and cereal rye (Secale cereale L.) cover crops on nitrate-N (NO3 -N) and total reactive phosphorus (TRP) loss via subsurface drainage. The study was evaluated from 2008 through 2015 using 36 0.4-ha plots outfitted with a subsurface drainage water quality monitoring system. Results showed that when swine manure was applied before both corn (Zea mays L.) and soybean [Glycine max (L.) Merr.], drainage water had significantly higher 8-yr-average flow-weighted NO3 -N concentrations compared with swine manure applied before corn only in a corn-soybean rotation. The lowest NO3 -N loss was 15.2 kg N ha-1  yr-1 from a no-till corn-soybean treatment with rye cover crop and spring application of urea-ammonium nitrate (UAN) to corn. The highest NO3 -N loss was 29.5 kg N ha-1  yr-1 from swine manure applied to both corn and soybean. A rye cover crop reduced NO3 -N loss, whereas tillage and residue management had little impact on NO3 -N loss. Losses of TRP averaged <32 g P ha-1  yr-1 from all treatments. Corn yield was negatively affected by both no-till management and cereal rye cover crops. Results showed that cropping management affected N leaching but impacts on P leaching were minimal.


Assuntos
Agricultura , Qualidade da Água , Animais , Nitrogênio/análise , Soja , Suínos , Zea mays
6.
J Environ Qual ; 49(1): 152-162, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-33016367

RESUMO

Pesticides are important for agriculture in the United States, and atrazine is one of the most widely used and widely detected pesticides in surface water. A better understanding of the mechanisms by which atrazine and its degradation product, deethylatrazine, increase and decrease in surface waters can help inform future decisions for water quality improvement. This study considers causal factors for trends in pesticide concentration in U.S. streams and models the causal factors, other than use, in structural equation models. The structural equation models use a concomitant trend in corn (Zea mays L.) and a latent variable model, indicating moisture supply and management. The moisture supply and management latent variable model incorporates long-term moisture conditions in the individual watersheds by using the Palmer hydrologic drought index, human influence on the hydrologic cycle through the percentage of the watershed drained by tile drains in 2012, and the base-flow contribution to streamflow, using the base-flow index. The structural equation models explain 77 and 38% of the variability in atrazine and deethylatrazine trends, respectively, across the conterminous United States. The models highlight future water quality challenges, particularly in tile-drained settings where fall precipitation and heavy precipitation are increasing.


Assuntos
Atrazina/análise , Praguicidas/análise , Poluentes Químicos da Água/análise , Agricultura , Atrazina/análogos & derivados , Estados Unidos
7.
J Environ Qual ; 49(3): 675-687, 2020 May.
Artigo em Inglês | MEDLINE | ID: mdl-33016383

RESUMO

Legacy phosphorus (P) in agricultural soils can be transported to surface waters via runoff and tile drainage, where it contributes to the development of harmful and nuisance algal blooms and hypoxia. However, a limited understanding of legacy P loss dynamics impedes the identification of mitigation strategies. Edge-of-field data from 41 agricultural fields in northwestern Ohio, USA, were used to develop regressions between legacy P concentrations (C) and discharge (Q) for two P fractions: total P (TP) and dissolved reactive P (DRP). Tile drainage TP concentration (CTP ) and DRP concentration (CDRP ) both increased as Q increased, and CTP tended to increase at a greater rate than CDRP . Surface runoff showed greater variation in C-Q regressions, indicating that the response of TP and DRP to elevated Q was field specific. The relative variability of C and Q was explored using a ratio of CVs (CVC /CVQ ), which indicated that tile drainage TP and DRP losses were chemodynamic, whereas losses via surface runoff demonstrated both chemodynamic and chemostatic behavior. The chemodynamic behavior indicated that legacy P losses were strongly influenced by variation in P source availability and transport pathways. In addition, legacy P source size influenced C, as demonstrated by a positive relationship between soil-test P and the CTP and CDRP in both tile drainage and surface runoff. Progress towards legacy P mitigation will require further characterization of the drivers of variability in CTP and CDRP , including weather-, soil-, and management-related factors.


Assuntos
Fósforo/análise , Movimentos da Água , Agricultura , Ohio , Solo
8.
J Environ Qual ; 49(3): 582-592, 2020 May.
Artigo em Inglês | MEDLINE | ID: mdl-33016386

RESUMO

We developed a GIS-based tool that values, in a spatially explicit way, the ecosystem services generated by water quality improvements resulting from adoption of agricultural best management practices (BMPs). The tool is calibrated for watersheds in the Chesapeake Bay drainage and includes the benefits from water quality improvements within targeted watersheds, water quality improvements downstream from targeted watersheds, and reductions in pollutant loadings to Chesapeake Bay. The tool is used to investigate specific BMP scenarios adopted within specific watersheds. The results show that (i) BMP adoption generates large positive net benefits to society, with benefit/cost ratios ranging from 22 to 276; (ii) by selecting cost effective BMPs and placing them in the most appropriate places, the cost of meeting pollutant reduction targets would be reduced by 34-71%; and (iii) net benefits from BMP adoption are higher when they are implemented close to or upstream from population centers.


Assuntos
Ecossistema , Qualidade da Água , Agricultura , Água , Abastecimento de Água
9.
J Environ Qual ; 49(3): 517-533, 2020 May.
Artigo em Inglês | MEDLINE | ID: mdl-33016389

RESUMO

Nutrient pollution is considered a wicked problem because of its many significant economic, social, and environmental impacts that are caused by multiple pollutants originating from a variety of sources and pathways that exist across different temporal and spatial scales. Further adding to the difficulty in managing nutrient pollution is that it is a global, rural, and urban problem. A systems approach can improve nutrient management by incorporating technological, environmental, and societal considerations. This approach can consider valuation of monetized and nonmonetized co-benefits and the inherent consequences that make up a nutrient management program. In this introduction to a special collection of papers on nutrient pollution, we describe several systems frameworks that can be used to support nutrient management and evaluation of system performance as it relates to impacts, then highlight several attributes and barriers of nutrient management that point to the need for a systems framework, and conclude with thoughts on implementing systems approaches to nutrient management with effective community engagement and use of new technologies. This special collection presents results from a USEPA Science to Achieve Results (STAR) initiative to advance solutions to nutrient pollution through innovative and sustainable research and demonstration projects for nutrient management based on a systems approach. These studies evaluate several promising nutrient control technologies for stormwater or domestic wastewater, investigate the effects of agricultural conservation practices and stream restoration strategies on nutrient loads, and discuss several challenges and opportunities-social, policy, institutional, and financial considerations-that can accelerate adoption of reliable technologies to achieve system-level outcomes.


Assuntos
Nutrientes , Rios , Agricultura , Análise de Sistemas , Águas Residuárias
10.
J Environ Qual ; 49(3): 769-773, 2020 May.
Artigo em Inglês | MEDLINE | ID: mdl-33016393

RESUMO

Closed-chamber methodology is widely used for the estimation of greenhouse gas (GHG) emissions in agricultural systems. The volume displaced by plants inside chambers influences GHG flux estimation, although generally it is not discounted from chamber headspace in the calculation. A novel image analysis-based procedure is proposed to estimate plant volume and to assess its impact on nitrous oxide (N2 O) flux estimations in a wheat (Triticum aestivum L. 'Rimbaud') crop. A maximum of 2.2% of the 13-L chambers was displaced by plants, leading to a systematic 0.9% overestimation in cumulative N2 O emissions if plant volume was not considered. Thus, plant canopy volume should be taken into account for improving the accuracy of emissions.


Assuntos
Gases de Efeito Estufa , Óxido Nitroso/análise , Agricultura , Triticum
11.
J Environ Qual ; 49(3): 663-674, 2020 May.
Artigo em Inglês | MEDLINE | ID: mdl-33016402

RESUMO

The impacts of low-disturbance manure application (LDMA) on runoff water quality in hay crop forages are not well known. Our objective in this study was to determine surface runoff losses of total nitrogen (TN), ammonium N (NH4 -N), nitrate N (NO3 -N), total phosphorus (TP), dissolved reactive P (DRP), and suspended sediment from alfalfa (Medicago sativa L.)-grass plots in central Wisconsin after surface broadcasting manure and LDMA compared with no application. Treatments were (a) surface banding (BAND), (b) surface banding with aeration (A/B), (c) shallow disk injection (INJECT), (d) surface broadcast (BCAST), and (e) a no-manure control (CONT). Runoff events were generated (n = 7) from replicated plots following a standardized rainfall simulation protocol. Although runoff was variable across plots and within treatments, mean runoff concentrations of TN (P = .03), NH4 -N (P = .03), TP (P = .001), and DRP (P < .0001) were lower for incorporated (INJECT and A/B) vs. unincorporated (BCAST and BAND) treatments. INJECT had lower mean DRP concentration (P = .02) than A/B and was similar to CONT and had lower cumulative TN (P = .05), TP (P = .07), and DRP (P = .01) loads than A/B. Additionally, TP, TN, DRP, and NH4 -N loads and concentrations were strongly related with soil surface manure coverage extent (R2 = 0.50-0.84; P < .0001), suggesting that manure was a main source of N and P losses. Although INJECT appeared to be the most effective in mitigating nutrient loss in surface runoff, more research is needed to determine LDMA impacts on farm economics, soil properties, and runoff water quality.


Assuntos
Esterco , Qualidade da Água , Agricultura , Medicago sativa , Chuva , Movimentos da Água , Wisconsin
12.
J Environ Qual ; 49(2): 292-303, 2020 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-33016415

RESUMO

Artificial subsurface drainage is necessary to maintain agricultural production in the soils and climate of north-central Iowa. However, it can result in adverse environmental impacts, because it intercepts and diverts some water and soluble NO3 -N directly to streams. We investigated the impact of no-till and a winter rye cover crop (Secale cereale L.) on seasonal and annual NO3 -N concentration and loading in leachate from a corn (Zea mays L.)-soybean [Glycine max (L.) Merr.] rotation. The eight treatments are chisel plow (CT), chisel plow with winter cereal rye (CTr), no-till (NT), and no-till with winter cereal rye (NTr), with "-C" indicating corn and "-S" indicating soybeans. Plots with artificial subsurface drainage were monitored for water quality from 2011 to 2015. The NT and CTr treatments consistently decreased NO3 -N loss on the seasonal and annual scales compared with CT. Compared with NT, NTr did not reduce NO3 -N loading nor concentration in leachate, probably because of low NO3 leaching potential from NT combined with low rye cover crop biomass throughout the study with NT. The 5-yr average annual NO3 -N concentrations were: 16.9 mg L-1 with CT-S, 16.7 mg L-1 with CT-C, 12.6 mg L-1 with NT-S, 12.0 mg L-1 with CTr-S, 11.8 mg L-1 with CTr-C, 11.4 mg L-1 with NTr-S and NTr-C, and 11.1 mg L-1 with NT-C. Overall, both no-till and a cover crop showed potential for improving N management for water quality.


Assuntos
Nitrogênio/análise , Secale , Agricultura , Iowa , Estações do Ano
13.
J Environ Qual ; 49(2): 392-403, 2020 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-33016417

RESUMO

Numerous studies have documented the linkages between agricultural nitrogen loads and surface water degradation. In contrast, potential water quality improvements due to agricultural best management practices are difficult to detect because of the confounding effect of background nitrate removal rates, as well as the groundwater-driven delay between land surface action and stream response. To characterize background controls on nitrate removal in two agricultural catchments, we calibrated groundwater travel time distributions with subsurface environmental tracer data to quantify the lag time between historic agricultural inputs and measured baseflow nitrate. We then estimated spatially distributed loading to the water table from nitrate measurements at monitoring wells, using machine learning techniques to extrapolate the loading to unmonitored portions of the catchment to subsequently estimate catchment removal controls. Multiple models agree that in-stream processes remove as much as 75% of incoming loads for one subcatchment while removing <20% of incoming loads for the other. The use of a spatially variable loading field did not result in meaningfully different optimized parameter estimates or model performance when compared with spatially constant loading derived directly from a county-scale agricultural nitrogen budget. Although previous studies using individual well measurements have shown that subsurface denitrification due to contact with a reducing argillaceous confining unit plays an important role in nitrate removal, the catchment-scale contribution of this process is difficult to quantify given the available data. Nonetheless, the study provides a baseline characterization of nitrate transport timescales and removal mechanisms that will support future efforts to detect water quality benefits from ongoing best management practice implementation.


Assuntos
Monitoramento Ambiental , Água Subterrânea , Agricultura , Nitratos/análise , Rios
14.
J Environ Qual ; 49(2): 496-508, 2020 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-33016424

RESUMO

Phosphorus (P) loss from agricultural fields contributes to water quality degradation. A phosphorus index (PI) is a tool that scores fields based on P loss potential. Recently, a new transport × best or beneficial management practice (BMP) approach was proposed for the New York PI (NY-PI), which first scores fields using landscape-based transport factors (raw scores) and then offers various BMPs to reduce the score (i.e., risk of P transport). The final score is assigned a management implication (N needs based, P removal based, or zero P application), taking into account field-specific soil-test P (STP) and the farm's whole-farm P balance. With farmer and nutrient management planner input and data on field-specific transport factors and whole-farm P balances of 18 New York dairy farms, we set coefficients for transport factors, BMPs related to P application, and STP limits and determined the impact of implementation of the new NY-PI on manure management options. Based on raw scores, the proposed NY-PI initially limited manure application to 51% of the total cropland area of the participating farms (28% N-based, 23% P-based). Implementation of BMPs (i.e., changing the method and ground cover or timing of P application) allowed 43-98% of the land area to receive manure at N-based rates. For farms with whole-farm P balances within the feasible limits set for New York, an additional 0-50% of the land base was classified as N-based management, depending on BMP selection. These results show the ability of the new NY-PI to limit P applications on fields with high transport risk while incentivizing adoption of BMPs and improvements in whole-farm P management.


Assuntos
Esterco , Fósforo/análise , Agricultura , Fazendas , New York , Medição de Risco
15.
J Environ Qual ; 49(2): 440-449, 2020 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-33016427

RESUMO

The use of suctions cups is a common practice for estimating nitrate (NO3 -N) leaching under agricultural systems despite the various uncertainties associated with the approach. One major uncertainty is water flux, which is required for calculating NO3 -N leaching loads from measured concentrations. Another problem is the interpolation of NO3 -N concentrations between measurement days. We investigated how differences in water flux, obtained from two different models (EVACROP and APSIM), affect NO3 -N leaching loads. The effect of interpolation of NO3 -N concentrations based on days or drainage was also addressed. The models were set up according to a 2-yr field experiment with spring barley (Hordeum vulgare L. Quinch) with different levels of N fertilization rates on a loamy soil at Flakkebjerg, Denmark. Due to small differences in measured NO3 -N concentrations between sequential samplings, the method of interpolation did not significantly affect NO3 -N leaching in the two periods investigated. Although there is no standard against which leaching losses from different approaches can be tested, results highlight that the modeling of water uptake as affected by N supply influences the amount of drainage and thus calculated NO3 -N leaching. Therefore, for experiments with varying N fertilization levels, the APSIM model, which accounts for N nutrition on crop water use, is likely more accurate. For common fertilization rates, the simpler EVACROP seems appropriate. Thus, when using suction cup data for testing models or for evaluating mitigation options for nitrate leaching, the use of an appropriate model for estimating water fluxes is important.


Assuntos
Fertilizantes/análise , Nitratos/análise , Agricultura , Solo , Sucção
16.
J Environ Qual ; 49(2): 304-313, 2020 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-33016428

RESUMO

Excess nitrogen (N) loading in the Mississippi River basin is a major water quality issue, encompassing large spatial scales and feedbacks between social and biophysical entities. Effective management depends on reductions in agricultural N loading, mainly from the Corn Belt region in the upper reaches of the basin. In this study, we evaluated the role of federal Nutrient Task Force policy on N management from 2000 to 2015. We analyzed trends in nitrate (NO3 - ) concentrations from monitoring data in 148 priority watersheds. We compared water quality trends with state nutrient reduction strategies, monitoring efforts, and land use. Of the 148 watersheds, 13 displayed a significant decrease in NO3 - concentrations, 24 displayed a significant increase, 51 displayed a nonsignificant trend, and 60 had insufficient data to analyze. We demonstrate that policy efforts on a large scale are slow to establish, but states and watersheds that showed signs of policy acting successfully could serve as examples for improved N management moving forward. Despite considerable variability, states with the most comprehensive strategies, evidenced by word count and presence of recommended elements, were almost exclusively located in the Corn Belt region. States with more thorough nutrient reduction strategies also tended to have a larger number of monitoring sites in priority watersheds (R = .42), demonstrating the potential for adaptive management. States with the most consistent improvements in NO3 - concentrations tended to have the most comprehensive policies, whereas variation in water quality trends was partly attributed to land use factors including slope and dominance of corn (Zea mays L.) and soy [Glycine max (L.) Merr.].


Assuntos
Nitrogênio/análise , Rios , Agricultura , Mississippi , Qualidade da Água
17.
J Environ Qual ; 49(2): 472-482, 2020 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-33016429

RESUMO

Manure elemental composition determination is essential to develop farm nutrient budgets and assess environmental risk. Portable X-ray fluorescence (PXRF) spectrometers could facilitate hazardous waste-free, rapid, and cost-effective elemental concentration determinations. However, sample moisture is a problem for elemental concentration determination by X-ray methods. The objective of this study was to quantify the effect of sample moisture content, predict moisture content, and correct for moisture effect on elemental concentration determinations in livestock manure. Oven-dried manure samples (n = 40) were ground and adjusted to five moisture ranges of (w/w moisture) <10%, 10-20%, 20-30%, 40-50%, and 60-70%. Samples were scanned by PXRF for 180 s using a vacuum (<1,333 Pa) and without a filter. The presence of moisture negatively affected elemental determination in manure samples. Calibrations (n = 200) were prepared using random forest regression with detector channel counts as independent variables. A three-step validation was performed using all the data, random cross-validation and external validation. The back end of the spectrum (14-15 keV) had strong predictive power (r2  = .98) for moisture content. The random forest approach increased r2 between PXRF and wet chemical methods from <.66 to >.90 for P, K, and Mg and from .78 to .98 for Fe, compared with linear, nonlinear, and Lucas-Tooth and Price equations. These results indicated that elemental concentration can accurately be measured in dried and moist manure samples using PXRF and expands the potential applications of PXRF to in situ elemental determinations for agricultural and environmental samples.


Assuntos
Esterco , Poluentes do Solo/análise , Agricultura , Animais , Monitoramento Ambiental , Espectrometria por Raios X
18.
J Environ Qual ; 49(2): 281-291, 2020 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-33016433

RESUMO

Nitrogen (N) loss from cropping systems has important environmental implications, including contamination of drinking water with nitrate. A 2-yr study evaluated the effects of six N rate, source, and timing treatments, including a variable rate (VR) N treatment based on the N sufficiency index approach using remote sensing, and two irrigation rate treatments, including conventional and reduced rate, on nitrate leaching, residual soil nitrate, and plant N uptake for potato (Solanum tuberosum L. cv. Russet Burbank) production in 2016 and 2017 on a Hubbard loamy sand. Nitrate leaching losses measured with suction-cup lysimeters varied between 2016 and 2017 with flow-weighted mean nitrate N concentrations of 5.6 and 12.8 mg N L-1 , respectively, and increased from 7.1 to 10.4 mg N L-1 as N rate increased from 45 to 270 kg N ha-1 . Despite reductions in N rate of 22 and 44 kg N ha-1 in 2016 and 2017, respectively, for the VR N treatment, there was no significant difference in nitrate leaching compared with the existing N best management practices (BMPs). Reducing irrigation rate by 15% decreased nitrate leaching load by 17% through a reduction in percolation. Residual soil nitrate N in the top 60 cm across all treatments (7.9 mg N kg-1 ) suggests a risk for nitrate leaching during the nongrowing season, and plant N uptake did not explain yearly variation in nitrate leaching and residual soil nitrate. Although existing N BMPs are effective at controlling N losses, development of alternative practices is needed to further reduce the risk of groundwater contamination.


Assuntos
Solanum tuberosum , Agricultura , Fertilizantes , Nitratos , Nitrogênio
19.
J Environ Qual ; 49(5): 1273-1285, 2020 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-33016436

RESUMO

Artificial subsurface (tile) drainage systems can convey phosphorus (P) from agricultural fields to surface waters; however, controls of subsurface dissolved reactive P (DRP) losses at the sub-field scale are not fully understood. We characterized subsurface DRP loads and flow-weighted mean concentration (FWMC) from January 2015 through September 2017 to determine seasonal (growing vs. non-growing) patterns from 36 individually monitored plots across a farm under a corn (Zea mays L.) and soybean [Glycine max (L.) Merr.] rotation in east-central Illinois. Using linear mixed models, we investigated the effects of soil test P (STP), depression depth, and their interaction with precipitation and P fertilization on subsurface DRP losses. Dissolved reactive P loads in drainage tiles increased with precipitation and were greatest during the non-growing season (NGS) in 2016 and 2017. Annual subsurface DRP loads were positively related to STP, and during the NGS, there was a positive relationship between depression depth quantified at the plot-scale and subsurface DRP loads and FWMC. Along a depression-depth gradient, piecewise regression displayed a threshold at a depth of 0.38 m at which STP increased, indicating soil P accumulation in deeper closed depressions. Our study highlights the need to identify areas with the greatest risk of subsurface P losses to implement sub-field scale nutrient management practices.


Assuntos
Fósforo/análise , Solo , Agricultura , Depressão , Illinois , Movimentos da Água
20.
J Environ Qual ; 49(5): 1370-1383, 2020 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-33016447

RESUMO

Recent research on tile-drainage has placed emphasis on dissolved reactive phosphorus (DRP) delivery and transport pathways but less emphasis on particulate P (PP), resulting in its exclusion from agricultural water management models. In this study, we quantified the fluxes, mechanisms, and factors driving PP delivery into tiles through statistical analysis of a long-term hydrologic and water quality dataset. The dataset includes 5 yr of surface and tile discharge, total P (TP), DRP, total nitrogen (TN), and dissolved inorganic N concentrations from two edge-of-field study sites with contrasting soil and management practices. Hydrograph recession techniques were coupled with multiple linear regression for understanding hydrologic flow pathways, and empirical mode decomposition (EMD) time-series analysis was used to determine the significance of PP seasonality processes and the effect of management practices. The analysis of hydrologic flow pathways demonstrated that quickflow contributed 66 and 36% of subsurface discharge in the clay and loam sites, respectively. Phosphorus loading analysis showed that macropore flow plays a significant role in PP delivery to subsurface P loading and that PP significantly contributed to TP and DRP delivery; however, greater PP loadings were observed at the clay site despite greater subsurface discharge and soil test P levels at the loam site. Furthermore, PP delivery was significantly affected by environmental conditions and management practices. We highlight the efficacy of hydrograph recession analysis for identifying macropore and diffuse drainage, of P/N ratios to characterize sediment delivery mechanisms in tiles, and of EMD to detect management impacts on TP and DRP at the field scale.


Assuntos
Fósforo/análise , Movimentos da Água , Agricultura , Hidrologia , Solo
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