00437nam a2200169Ia 4500008004100000082001800041100002300059245003200082250000900114260003600123650002000159650001700179650001600196650001800212650002000230650001700250220204s9999    xx            000 0 und d  a631.6.02bTRO  aTroeh, Frederick R 0aSoil and water conservation  aEd.2  aNew JerseybPrentice Hallc1980  aCropping system  aSoil erosion  aSoil survey  aWater erosion  aWater pollution  aWind erosion