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Analyse et modélisation de l'évolution des indicateurs de la fertilité des sols cultivés en zone cotonnière du Togo / Analyze and simulation a dynamic of soil indicators fertility under different agricultural management practices in cotton area of TogoKintche, Kokou 24 November 2011 (has links)
Des données synchroniques de sols observées pendant 20 à 40 ans dans différentes zones agro-écologiques du Togo ont été utilisées pour analyser l’évolution de la fertilité du sol sous différentes pratiques culturales. Trois modèles de complexité croissante d’évolution du stock de C du sol ont été testés et le plus performant a été couplé au modèle QUEFTS pour apprécier l’effet des pratiques culturales sur l’évolution de cette fertilité. Bien que la fertilisation NPK ait été continuellement appliquée à la dose recommandée par la recherche (RR) ou à cette dose augmentée de 50% (1.5RR), les rendements initiaux de 1,5 à 2 t ha-1 pour le coton et 2 à 3 t ha-1 pour les céréales ont baissé pour ne représenter qu’environ 1 t ha-1 après 20 années de culture. L’alternance de 2 ou 3 années consécutives de jachère à la rotation culturale n’a pas amélioré le rendement des cultures, mais tend à stabiliser la production dans le long terme. Les stocks initiaux de C de 15 à 39 t ha-1 ont fortement baissé durant les premières années et ont atteint un équilibre après seulement 10 à 15 ans de culture. La baisse du stock de C a été peu dépendante de la quantité de C retournant au sol et a été mieux décrite avec le modèle à deux compartiments de C. Le taux de minéralisation de la fraction labile de C varie entre 0,15 et 0,24 et le stock de C stable représente 33-67% du stock initial ; pour une quantité de C ayant résisté à l’hydrolyse acide de 30% du stock initial. Les stocks de N du sol ont fortement baissé et cette baisse a été peu dépendante de la dose de fertilisation minérale. L’apport NPK à 1.5RR pendant 20 ans a contribué significativement à la baisse du pH du sol, puis a accentué de 20 et 40% les baisses respectives des concentrations de Ca et Mg. Nous avons conclu que l’apport de Ca/Mg couplé à celui de NPK à la dose RR serait (plus que le surdosage de P et K) une meilleure option pour gérer la fertilité minérale de ces sols. Le labour minimum, associé aux apports externes de C, devrait permettre de mieux gérer leur fertilité organique. / Using data observed during 20 to 40 years in different agro-ecosystems of Togo, we analyzed soil fertility dynamic under different agricultural management practices. Tree soil C models of varying complexity were tested, and the most accurate in terms of soil C dynamics description in these tropical soils was associated with the QUEFTS model and with nutrient partial balance to analyze the effect of each agricultural management practice. Results indicated that, although fertilizers N, P and K were continuously applied at a recommended rate by the research (RR) or at this rate increased in 50% (1.5RR), initial cotton and cereals yields of 1.5 to 2 t ha˗1 and 2 to 3 t ha˗1, respectively, decreased to around 1 t ha-1 after 20 years of soil cultivation. Alternation of 2 or 3 consecutive years of fallow plot with 3 years cropping did not improved crops yields as compared with continuous cropping system, but tends to stabilize crops production in the long-term. In the upper soil 20 cm, soil C stock of 15 to 39 t ha˗1 after vegetation clearance dropped faster during the first years to reached equilibrium after only 10 to 15 years of soil cultivation. Such a decrease was less depended on soil C input and was accurately descried with a two-pool C model, running on an annual time step basis. Calibrated decomposition rate of labile soil C ranged between 0.15 and 0.24, and stable soil C pool represented 33 to 67% of initial total C; while soil C that was resistant for hydrolyze acid was about 30% of initial total C. Soil N stock was also decreased faster and less associated with a rate of N input to soil. Application of NPK at 1.5RR during 20 years contributed significantly to soil pH decrease and pronounced soil Ca and Mg decreases, which respectively were 20 and 40% more than in plots that were not fertilized. We concluded that, association of Ca/Mg and NPK at a recommended rate would be (more than over-dosage of P and K) a promising option to achieving a sustainable management of mineral fertility of these soils. Minimum tillage, associated with external C input, would be an asset to a sustainable management of organic fertility of these soils.
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Bacterial diversity and denitrifier communities in arable soilsCoyotzi Alcaraz, Sara Victoria January 2014 (has links)
Agricultural management is essential for achieving optimum crop production and maintaining soil quality. Soil microorganisms are responsible for nutrient cycling and are an important consideration for effective soil management. The overall goal of the present research was to better understand microbial communities in agricultural soils as they relate to soil management practices. For this, we evaluated the differential impact of two contrasting drainage practices on microbial community composition and characterized active denitrifiers from selected agricultural sites.
Field drainage is important for crop growth in arable soils. Controlled and uncontrolled tile drainage practices maintain water in the field or fully drain it, respectively. Because soil water content influences nutrient concentration, moisture, and oxygen availability, the effects of these two disparate practices on microbial community composition was compared in paired fields that had diverse land management histories. Libraries of the 16S rRNA gene were generated from DNA from 168 soil samples collected from eight fields during the 2012 growing season. Paired-end sequencing using next-generation sequencing was followed by read assembly and multivariate statistical analyses. Results showed that drainage practice exerted no measureable effect on the bacterial communities. However, bacterial communities were impacted by plant cultivar and applied fertilizer, in addition to sampled soil depth. Indicator species were only recovered for depth; plant cultivar or applied fertilizer type had no strong and specific indicator species. Among indicator species for soil depth (30-90 cm) were Chloroflexi (Anaerolineae), Betaproteobacteria (Janthinobacterium, Herminiimonas, Rhodoferax, Polaromonas), Deltaproteobacteria (Anaeromyxobacter, Geobacter), Alphaproteobacteria (Novosphingobium, Rhodobacter), and Actinobacteria (Promicromonospora).
Denitrification in agricultural fields transforms nitrogen applied as fertilizer, reduces crop production, and emits N2O, which is a potent greenhouse gas. Agriculture is the highest anthropogenic source of N2O, which underlines the importance of understanding the microbiology of denitrification for reducing greenhouse gas emissions by altered management practices. Existing denitrifier probes and primers are biased due to their development based mostly on sequence information from cultured denitrifiers. To circumvent this limitation, this study investigated active and uncultivated denitrifiers from two agricultural sites in Ottawa, Ontario. Using DNA stable-isotope probing, we enriched nucleic acids from active soil denitrifiers by exposing intact replicate soil cores to NO3- and 13C6-glucose under anoxic conditions using flow-through reactors, with parallel native substrate controls. Spectrophotometric chemistry assays and gas chromatography confirmed active NO3- depletion and N2O production, respectively. Duplicate flow-through reactors were sacrificed after one and four week incubation periods to assess temporal changes due to food web dynamics. Soil DNA was extracted and processed by density gradient ultracentrifugation, followed by fractionation to separate DNA contributed by active denitrifiers (i.e., “heavy” DNA) from that of the background community (i.e., “light” DNA). Light and heavy DNA samples were analyzed by paired-end sequencing of 16S rRNA genes using next-generation sequencing. Multivariate statistics of assembled 16S rRNA genes confirmed unique taxonomic representation in heavy fractions from flow-through reactors fed 13C6-glucose, which exceeded any site-specific or temporal shifts in putative denitrifiers. Based on high relative abundance in heavy DNA, labelled taxa affiliated with the Betaproteobacteria (71%; Janthinobacterium, Acidovorax, Azoarcus, Dechloromonas), Alphaproteobacteria (8%; Rhizobium), Gammaproteobacteria (4%; Pseudomonas), and Actinobacteria (4%; Streptomycetaceae). Metagenomic DNA from the original soil and recovered heavy fractions were subjected to next-generation sequencing and the results demonstrated enrichment of denitrification genes with taxonomic affiliations to Brucella, Ralstonia, and Chromobacterium in heavy fractions of flow-through reactors fed 13C6-glucose. The vast majority of heavy-DNA-associated nitrite-reductase reads annotated to the copper-containing form (nirK), rather than the heme-containing enzyme (nirS). Analysis of recovered nirK genes demonstrated low sequence identity across common primer-binding sites used for the detection and quantification of soil denitrifiers, indicating that these active denitrifiers would not have been detected in molecular surveys of these same soils.
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Water Risk Assessment of Agricultural Raw Materials in a Global Supply Chain : A Case Study of IKEA / Bedömning av vattenrisker för jordbruksråmaterial i en global värdekedja : En fallstudie på IKEABerggren, Victoria January 2022 (has links)
Current mass consumption and production patterns have led to an unsustainable use of natural resources, including freshwater, which is one the most crucial natural resources for people and the planet. Agricultural production systems are alone responsible for 72 percent of all global water withdrawals. Therefore, companies with an agricultural supply chain, such as IKEA, play an important role in minimising the negative impacts on water due to agricultural production. In order to do so, companies need to conduct assessments to become aware of their contribution and thereafter develop water targets and strategies on how to mitigate and minimise the company’s water impacts. Several different guidances, methodologies, and tools aiding companies in how to do this have recently been developed, however there is not yet one common established methodology. Therefore, this research project aimed to test and evaluate a new assessment methodology and tool for IKEA, by conducting a water risk assessment on water availability of the sourcing locations of two of IKEA’s key agricultural raw materials: soy and palm oil, and identifying mitigation possibilities, in order to aid in the company’s further work with achieving a sustainable water management and material sourcing, and developing water targets and strategies. Soy is a prioritised raw material to work with in terms of environmental and social risk, and through the conducted water risk assessment, a high risk for water depletion was identified in many of the company’s most likely sourcing locations. The water risk assessment results for palm oil indicated no significant risk for water depletion in any of the sourcing locations. The high water depletion risk scores of the hotspots were found to most likely be due to several different causes, both climatic conditions and anthropogenic activities, including agriculture. Therefore, it was identified that there are possibilities for a company, such as IKEA, to aid in mitigating the water availability challenge of the hotspots through the company’s agricultural supply chain. For example, a few agricultural management practices for increasing the water use efficiency suitable for the different hotspots could be recommended and incentivised by the company to the local farmers of the hotspot sourcing locations. The WRA methodology used in this research project, following the guidance for setting enterprise water targets by Reig et al. (2021), was assumed suitable for IKEA to use and incorporate into a more comprehensive environmental assessment methodology for agricultural raw materials in order to develop water targets and strategies. The Aqueduct Food tool was assumed to be a robust tool for water risk assessment, and can be a suitable tool for IKEA to use to quickly gain a high-level picture of a material, location or water risk of specific interest. The water risk assessment results will mainly be useful in the future, when more comprehensive environmental assessments of agricultural raw materials have been conducted, and the water use has been assessed to a greater extent. Future research is needed to be conducted in order to confirm the results and recommendations of this research project, as well as to further complement the results for the needs of IKEA. This future research includes conducting field studies of the identified hotspots and the operations of the local farms, and conducting an equivalent water risk assessment of the two materials and sourcing locations on the water quality. / Nuvarande masskonsumtion och produktionsmönster har lett till en ohållbar användning av naturresurser, inklusive sötvatten, som är en av de mest avgörande naturresurserna för människor och planeten. Jordbruk står ensam för 72 procent av alla globala vattenuttag. Därför har företag med en jordbruksförsörjningskedja, som IKEA, en viktig roll i att hjälpa till att minska de negativa effekterna på vatten från jordbruk. För att kunna göra det behöver företag utföra bedömningar för att bli medvetna om sin vattenpåverkan och därefter utveckla vattenmål och strategier för hur de kan minimera den påverkan. Det har nyligen utvecklats flera olika vägledningar, metodiker och verktyg som hjälper företag att göra detta, men det finns ännu inte en gemensam etablerad metodik. Därför hade detta forskningsprojekt som syfte att testa och utvärdera en ny bedömningsmetodik och ett nytt verktyg för IKEA, genom att genomföra en riskbedömning av vattentillgången för produktionsplatserna för två av IKEAs viktigaste jordbruksråmaterial: soja och palmolja, och genom en litteraturstudie identifiera möjligheter att minska vattenpåverkan, för att bidra till företagets fortsatta arbete med att uppnå en hållbar vattenanvändning och materialförsörjning i jordbruksförsörjningskedjan och att utveckla vattenmål och strategier. Soja är ett prioriterat råmaterial att arbeta med gällande miljömässiga och sociala risker, och genom den genomförda bedömningen av vattenrisker identifierades en hög risk för vattenbrist på många av de produktionsplatser som företaget mest troligen köper in ifrån. Riskbedömningsresultaten för palmolja indikerade ingen signifikant risk för vattenbrist på någon av de produktionsplatser som företaget troligen köper in ifrån. Den höga risken för vattenbrist i de identifierade hotspotsen visade sig troligen bero på flera olika orsaker, både klimatförhållanden och antropogena aktiviteter, inklusive jordbruk. Därför identifierades det att det finns möjligheter för ett företag, som IKEA, att kunna hjälpa till att mildra vattentillgänglighetsutmaningen i hotspotsen genom företagets jordbruksförsörjningskedja. Till exempel kan ett par olika jordbruksförvaltningsmetoder för att öka vattenanvändningseffektiviteten som är lämpliga för de olika hotspotsen rekommenderas och uppmuntras av företaget till de lokala bönderna. Den WRA-metodik som används i detta forskningsprojekt, som följde vägledningen för att sätta upp vattenmål för företag av Reig et al. (2021), antogs lämplig för IKEA att använda och integrera i en mer omfattande miljöbedömningsmetodik för jordbruksråmaterial för att utveckla vattenmål och strategier. Aqueduct Food-verktyget antogs vara ett robust verktyg för riskbedömning för vatten och kan vara ett lämpligt verktyg för IKEA att använda för att snabbt få en översikt av ett material, en plats eller en vattenrisk av specifikt intresse. Riskbedömningsresultaten kommer främst att vara användbara i framtiden, när mer omfattande miljöbedömningar av jordbruksråvaror har gjorts och vattenanvändningen har bedömts i större utsträckning. Framtida forskning behövs för att bekräfta resultaten och rekommendationerna i detta forskningsprojekt, samt för att ytterligare komplettera resultaten för IKEAs behov. Denna framtida forskning inkluderar att genomföra fältstudier av de identifierade hotspotsen och de lokala sojafarmernas verksamhet, och att genomföra en likvärdig riskbedömning för vatten av de två materialen och produktionsplatserna som utförts i detta forskningsprojekt för vattenkvaliteten.
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Nonpoint Source Pollutant Modeling in Small Agricultural Watersheds with the Water Erosion Prediction ProjectRyan McGehee (14054223) 04 November 2022 (has links)
<p>Current watershed-scale, nonpoint source (NPS) pollution models do not represent the processes and impacts of agricultural best management practices (BMP) on water quality with sufficient detail. To begin addressing this gap, a novel process-based, watershed-scale, water quality model (WEPP-WQ) was developed based on the Water Erosion Prediction Project (WEPP) and the Soil and Water Assessment Tool (SWAT) models. The proposed model was validated at both hillslope and watershed scales for runoff, sediment, and both soluble and particulate forms of nitrogen and phosphorus. WEPP-WQ is now one of only two models which simulates BMP impacts on water quality in ‘high’ detail, and it is the only one not based on USLE sediment predictions. Model validations indicated that particulate nutrient predictions were better than soluble nutrient predictions for both nitrogen and phosphorus. Predictions of uniform conditions outperformed nonuniform conditions, and calibrated model simulations performed better than uncalibrated model simulations. Applications of these kinds of models in real-world, historical simulations are often limited by a lack of field-scale agricultural management inputs. Therefore, a prototype tool was developed to derive management inputs for hydrologic models from remotely sensed imagery at field-scale resolution. At present, only predictions of crop, cover crop, and tillage practice inference are supported and were validated at annual and average annual time intervals based on data availability for the various management endpoints. Extraction model training and validation were substantially limited by relatively small field areas in the observed management dataset. Both of these efforts contribute to computational modeling research and applications pertaining to agricultural systems and their impacts on the environment.</p>
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<strong>Agbufferbuilder for decision support in the collaborative design of variable-width conservation buffers in the Saginaw Bay watershed</strong>Patrick T Oelschlager (16636047) 03 August 2023 (has links)
<p>Field-edge buffers are a promising way to address nonpoint source pollution from agricultural runoff, but concentrated runoff flow often renders standard fixed-width linear buffers ineffective. AgBufferBuilder (ABB) is a tool within ESRI ArcMap Geographic Information Systems software that designs and evaluates targeted, nonlinear buffers based on hydrologic modeling and other field-specific parameters. We tested ABB on n=45 Areas of Interest (AOIs) stratified based on estimated sediment loading across three sub-watersheds within Michigan’s Saginaw Bay watershed to evaluate the effectiveness of ABB relative to existing practices across a wide range of landscape conditions. We modeled tractor movement around ABB buffer designs to assess more realistic versions of the likely final designs. ABB regularly failed to deliver the desired 75% sediment capture rate using default 9 m x 9 m output raster resolution, with Proposed buffers capturing from 0% to 68.49% of sediment within a given AOI (mean=37.56%). Differences in sediment capture between Proposed and Existing buffers (measured as Proposed – Existing) ranged from -48% to 66.81% of sediment (mean=24.70%). Proposed buffers were estimated to capture more sediment than Existing buffers in 37 of 45 AOIs, representing potential for real improvements over Existing buffers across the wider landscape. In 13 of 45 AOIs, ABB buffers modified for tractor movement captured more sediment than Existing buffers using less total buffer area. We conducted a collaborative design process with three Saginaw Bay watershed farmers to assess their willingness to implement ABB designs. Feedback indicated farmers may prefer in-field erosion control practices like cover cropping and grassed waterways over field-edge ABB designs. More farmer input is needed to better assess farmer perspectives on ABB buffers and to identify preferred data-based design alternatives. Engineered drainage systems with raised ditch berms and upslope catch basins piped underground directly into ditches were encountered several times during site visits. ABB only models surface flow and does not recognize drain output flow entering waterways. Modified ABB functionality that models buffers around drain inlets would greatly improve its functionality on drained sites. This may be accomplishable through modification of user-entered AOI margins but requires further investigation. Unfortunately, the existing tool is built for outdated software and is not widely accessible to non-expert users. We suggest that an update of this tool with additional functionality and user accessibility would be a useful addition in the toolbox of conservation professionals in agricultural landscapes.</p>
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