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  • Dissipation of soil-applied sugarcane herbicides in organic soilsCalvin Odero

    Certified Crop Adviser CEU Session

  • OutlineEverglades Agricultural Area (EAA)Organic soilsSugarcaneTaxonomy, crop cycleWeeds associated with sugarcaneBroadleaf, grass, and grass-like weedsWeed management in sugarcanePreemergence and postemergence herbicidesSoil herbicide dissipationTerminologies (degradation, dissipation, persistence)Factors affecting herbicides dissipationSoil, climatic, and herbicide propertiesSoil-applied herbicides in sugarcanePendimethalin, atrazine, metribuzinField dissipation of pendimethalin in organic soils of the EAAField dissipation of atrazine and metribuzin in organic soils of the EAA

  • Everglades Agricultural Area (EAA)700,000 acres of landMajor crop - sugarcaneOther crops - winter vegetables, rice, sodDominated by organic (muck) soilsSugarcane acreage325,000 acres on organic soils (Histosols)92,000 acres on mineral (sandy) soils (Spodosols & Entisols) Source: http://www.doi.gov/pmb/oepc/wetlands2/v2ch7.cfm

  • Organic soilsFormed several thousands of years Organic matter production exceeded decompositionFlooded sawgrass prairies south of Lake OkeechobeeHigh soil organic matter content (up to 85%)Soil depth6 inches to over 4 feet

  • Organic soil subsidence Drainage of soils resulted in Oxidation & mineralization of large quantities of organic NMicrobial oxidation account for 50 to 75% of the subsidenceSubsidence ratesEstimated using transect lines from the bedrock 1924 1967: 1.12 inches/year 1967 2009: 0.55 inches/yearReasons for declineMaintenance of high water table, BMPsIncreasing recalcitrate of remaining soil organic matterIncreased mineral content (CaCO3, sand, clay)9 foot post driven into the bedrock at the EREC in 1924

  • SugarcaneGiant grassFamily: PoaceaeTribe: Adropogoneae Saccharum officinarum L.Noble cane with long, thick, heavy, juicy & sweet stalks Other speciesS. barberiS. robustumS. sineseS. spontaneum Commercial clones are typically 3-part hybrids

  • SugarcanePerennial crop, harvested annually Planting seasonMid-October to end-DecemberFirst year crop is plant cane, successive years are ratoon or stubble crops Harvest seasonMid-October to March/AprilTypically replanted every 3 to 5 yearsPlantingFollowing fallow period after final ratoonCrop rotation (winter vegetables, rice), flooding, fallowSuccessiveReplanting several weeks after the final ratoon

  • Sugarcane planting

  • Common broadleaf weeds in sugarcaneCommon lambsquarters*Spiny amaranth*Common ragweed*Common purslaneAlligatorweedAmerican blacknightshade

    Common lambsquartersSpiny amaranth

  • Common grass and grass-like weeds in sugarcaneFall panicum*GuineagrassGoosegrassCrowfoot grassCrabgrassesBermudagrass*Almum sorghumElephantgrassYellow nutsedge*Purple nutsedgeFall panicumBermudagrass

  • Weed management in sugarcaneMajor cost associated with sugarcane productionWeed management methodsMechanical cultivation, herbicides, cultural (crop rotation) Herbicides are most commonly usedPreemergenceAtrazineMetribuzinPendimethalin

    Postemergence2,4-DDicambaAmetrynAtrazineMetribuzinMesotrioneAsulamTrifloxysulfuronHalosulfuron

    Mechanical cultivationCrop rotation (Sweet corn)Glyphosate

  • Herbicide application in sugarcane

  • TerminologiesSeveral related terms with respect to the residence time a herbicide remains in a given portion of the soil matrixDegradation: substantive change in the molecular makeup of a given herbicide, with a component of the parent molecule removed by some process to form a metabolite or metabolitesDissipation: sum of all possible outcomes of the parent herbicideNon-alteration of chemical form of the herbicideVolatilization, movement off-site, leaching, surface runoffChemical alteration of the chemical form of the herbicideChemical or microbial degradationPersistence: length of time a herbicide remains active in the soilCan be considered a negative connotationDamages to rotational crops, contamination of surface water and groundwaterAllow for residual weed controlHalf-life: amount of time required for dissipation of one half of the original amount of herbicide appliedSource: http://extension.psu.edu/pests/weeds/control/persistance-of-herbicides-in-soil

  • Herbicide families with their persistent members Herbicides vary in their potential to persist in soil

  • Soil factors affecting dissipationPhysicalCompositionRelative amounts of sand, silt, clay, organic matter Herbicidal activity is affected byAdsorption, leaching, volatilizationChemistrySoil pH, CEC, nutrient status Triazines and sulfonylureasMicrobial activityMicrobes (bacteria, fungi) and their relative numbersAffected byMoisture, pH, oxygen, mineral nutrient supply

  • Climatic factors affecting dissipationMoisture and temperatureDegradation rates affected by both factorsChemical and microbial decomposition increase with higher temperatures and moisture levelsSunlightPhotodecomposition Dinitroanilines (pendimethalin, trifluralin)

  • Herbicide properties affecting dissipationChemical propertiesWater solubility, vapor pressureSusceptibility to chemical or microbial alteration or degradationLeaching depends on Water solubility of the herbicideHerbicide-soil binding propertiesSoil physical characteristicsRainfall frequency and intensityHerbicide concentrationTime of herbicide applicationVolatilizationHigher vapor pressureThiocarbamates, dinitroanilinesHerbicides chemical structureDictates degradation in soil by microbial or chemical means

  • PendimethalinDinitroaniline herbicidePRE control of annual grasses, certain broadleaf weeds Chemical and physical propertiesCrystalline orange-yellow solid with faint nutty odorLow water solubility (0.275 mg L1)Low mobility and leaching potential Strong adsorption to soil colloids and OM (Koc = 17,200 L kg1) Low volatility (vapor pressure = 1.25 103 Pa)Characteristics are attributed to High potential for hydrogen bonding in particular to organic, lipophilic and proteinaceous substances Use rate increases with increasing soil OM

  • PendimethalinDegraded primarily by soil microorganisms Undergoes photodecomposition Persistence influenced by edaphic and climatic conditions Degradation is faster under anaerobic, warm and moist conditionsHalf-life42 to 101 days under laboratory conditions44 days in the fieldDepends on soil temperature and moistureBioavailability decreases with increase in soil organic matter content

  • Field dissipation of pendimethalinLocationBelle Glade, FL in 2011 and 2012Dania muck soil, pH of 7.1 and 6.6, OM of 68.1 and 73.9% Design: RCBD, 3 to 4 replicationsPendimethalin treatmentsOil-based formulation (Prowl 3.3 EC)Water-based formulation (Prowl H2O)2, 4, and 8 kg ha1 plus a nontreated controlSoil sampling7, 14, 21, 28, 35, 42, 49, and 56 days after treatmentFour soil cores, 0 to 10 cm in depthPendimethalin in soil was determined using a GC-MS

  • Environmental conditions at herbicide applicationOdero and Shaner, Weed Technology 28:82-88

  • Odero and Shaner, Weed Technology 28:82-88

  • SummaryRate of dissipation of oil- and water-based pendimethalin formulations was very similarInitial amount of pendimethalin in the soil was higher with the water-based compared to the oil-based formulationLower volatility of the water-basedLower half-life values for both pendimethalin formulations under field conditions Climatic and edaphic conditionsAbsence of incorporation following applicationConclusionGrowers on organic soils will not observe long residual activity of pendimethalin irrespective of the formulation when applied under dry soil conditions with no incorporation

  • Triazine herbicidesImportant in weed management in sugarcane Atrazine (s-triazine) is the most widely used>70% of the sugarcane acreage in the USOffers consistent performance, low cost, residual weed control, flexibility in time and method of application, compatibility with other herbicides, crop safety Metribuzin (asymmetrical triazine) is also used in sugarcane Both used for PRE or early POST for control of broadleaf weeds and certain grassesEfficacious residual weed control depends on their persistenceBoth have half-lives of up to 60 days under field conditions Relatively low adsorption on most soils Sugarcane growers have observed reduced residual activity of atrazine on organic soils of the EAA

  • AtrazinePersistence in soil attributed to the halogen, methylthiother, and N-alkyl substituents on the s-triazine ring which impeded microbial degradation but Adaptation of bacterial communities able to utilize atrazine as a C and N source has occurredSoils with repeated atrazine useEnhanced degradation Pseudomonas sp. strain ADP and Nocardioides sp. strain C190 able to metabolize and rapidly degrade atrazine have been isolatedEnhanced atrazine degradation has been reported Colorado, Mississippi, Ohio, TennesseeAustralia, Canada, Europe, South America Fields with a history of repeated atrazine use

  • Atrazine and metribuzinEnhanced atrazine degradation reported across the full range of sugarcane production areas Using laboratory incubation dissipation studies Atrazine-adapted soils were cross-adapted with ametryn (chloro-s-triazine) but not with metribuzin Lack of cross-adaptation of atrazine and metribuzin shows that metribuzin could be a viable alternative for use in sugarcane soils with enhanced atrazine degradation

  • Field dissipation of triazine herbicidesLocationBelle Glade, FL in 2011 and 2012Dania muck soil, pH of 7.1 and 6.6, OM of 68.1 and 73.9% Design: RCBD, 3 to 4 replicationsHerbicide treatmentsAtrazine - 2.24, 4.48, and 8.96 kg ha-1 Metribuzin - 0.56, 1.12, an

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