現(xiàn)代農(nóng)業(yè)生態(tài)系統(tǒng)概述-資料下載頁
2024-12-31 22:01本頁面
【正文】 ems.?RunoffofNandPintostreamscauseseutrophication.FertilizationbyN,P,andKcauseshigheryields,butwhenplantsareremoved,manycations(esp.CaandMg)areremoved.Thisincreasestheacidityofthesoil.SOILEROSION?Exposingbaresoiltotheelementsanddecreasinginfiltrationratescauseswindandwatererosion.ConservationReservePrograms,lowtilltechniques,increasinganicmatter,andplantingofhedgerowshavedecreasedthisproblem.MONOCULTURES?Plantingcropsinmonoculturesencouragespests,diseases,andcropfailure.Polyculturesallowplementarity,andaremakingaeback.GENETICEROSIONThegeicdiversityofdomesticanimalsandcropplantsisbeingdepleted.Genesforresistancetostressanddiseasearelost.ENERGETICSMost mechanized agriculture has moreenergyinputthanoutput.The nation is on a pesticide treadmill because pestsbeeresistanttotheeffectsofpesticides,requiringfarmsto adopt new and more potent poisons, to which pestseventuallybeeresistant.Thereisnoendtothistoxicspiral.Resistancecannotbeavoided。itisanaturalpartoftheevolutionaryprocess.When agroupofpestsisexposedtoatoxicchemical,someofthemsurvive.Thesehardyfewreproduceandtheiroffspringinheritgenesresistanttothisparticularchemical.Excessiveuseofapesticidespeedsuptheprocessbywhichpestsdevelopresistance.Morethan500insectshavenowdevelopedresistancetooneormorepesticides。 so have 270 species of weeds and 150 plantdiseases.謝謝觀看 /歡迎下載BY FAITH I MEAN A VISION OF GOOD ONE CHERISHES AND THE ENTHUSIASM THAT PUSHES ONE TO SEEK ITS FULFILLMENT REGARDLESS OF OBSTACLES. BY FAITH I BY FAITH
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