Fertilizer, tillage, and dairy manure contributions to nitrate and herbicide leaching.
Few studies have examined the water quality impact of manure use in no-tillage systems. A lysimeter study in continuous corn (Zea mays L.) was performed on Maury silt loam (fine, mixed, semiactive, mesic Typic Paleudalf) to evaluate the effect(s) of tillage (no-till [NT] and chisel-disk [CD]), nitrogen fertilizer rate (0 and 168 kg N ha(-1)), and dairy manure application timing (none, spring, fall, or fall plus spring) on NO3-N, atrazine (2-chloro-4-ethylamino-6-isopropylamino-s-triazine), and alachlor [2-chloro-2'-6'-diethyl-N-(methoxymethyl)acetanilide] concentrations in leachate collected at a 90-cm depth. Herbicides were highest immediately after application, declining to less than 4 mug L(-1) in about two months. Manure and manure timing by tillage interactions had little effect on leachate herbicides; rather, the data suggest that macropores rapidly transmitted atrazine and alachlor through the soil. Tillage usually did not significantly affect leachate NO3-N, but no-tillage tended to cause higher NO(3)-N. Manuring caused higher NO3-N concentrations; spring manuring had more impact than fall, but fall manure contained about 78% of the N found in spring manure. Nitrate under spring "only fertilizer" treatment exceeded 10 mg L(-1) 38% of the time, compared with 15% for spring only manure treatment. After three years, manured soil leachate NO3-N exceeded that for soil receiving only N fertilizer. Soil profile (90 cm) NO3-N after corn harvest exceeding 22 kg N ha(-1) was associated with winter leachate NO3-N greater than 10 mg N L(-1). Manure can be used effectively in conservation tillage systems on this and similar soils. Accounting for all N inputs, including previous manure applications, will be important.
University of California Cooperative Extension Service-Merced County, 2145 Wardrobe Avenue, Merced, CA 95340-6496, USA.
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D000383:Agriculture; D000818:Animals; D003612:Dairying; D005308:Fertilizers; D006540:Herbicides / Q000032:analysis* / Q000737:chemistry; D008372:Manure; D009566:Nitrates / Q000032:analysis* / Q000737:chemistry; D012621:Seasons; D012989:Soil Pollutants / Q000032:analysis*; D012995:Solubility; D014873:Water Pollutants / Q000032:analysis*; D003313:Zea mays / Q000254:growth & development
D005308:Fertilizers; D006540:Herbicides; D008372:Manure; D009566:Nitrates; D012989:Soil Pollutants; D014873:Water Pollutants