Ifyouwantyourlandtokeepfertile,youmusttrytostopsoilfrombeingcarriedawaybywaterorwind.Whensoilistakenawaybyflowingwaterorblowingwindswecallitsoilerosion.Wayshavebeenfoundtostopsoilerosion,andthisisknownassoilconservation.Onewayofstoppingsoilerosionistogrowsmallplantssuchasgrass.Theseplantsarereferredtoacovercrops,whoserootsholdthesoiltightlytogether.Therainwatercannotwashawaythesoil.Whentreesandtallbushesareplantedattheedgesofanopenfield,soilerosionbystrongwindscannottakeplace.Thetreesandbushes,whichactasaverybigandfirmwall,protecttheopenlandfromthewinds.Thewaytostoopsoilerosiononslopesistobuildterracesontheslopeofhillsideandmountainside.Whentheslopeofahillsideiscutinto“step”,watercarryingsoilcannotrunstraightdowntheterraces,whichareusedtoslowdownthespeedoftheflowingwatercontainingmuchsoilinit.Inthiswaymostofthesoilinthewaterisleftbehindontheterraces,muchsoilinit. |
A.Floodhappenstothefertileland |
B.Alargequantityofthesoillosesawaygradually. |
C.Terracesarebuiltontheslopeofhillsideormountainside. |
D.Plantsaregrowntoprotecttheopenland |
A.grass B.treesandbushes C.plantslifeandanarea
E. coveringplantsthatproducegrainorvegetables
小题3:Besidesgrowingsmallplants,anothermethodtofightagainstsoilerosionisto___________.