Fertilizer, Tillage, and Dairy Manure Contributions to Nitrate and Herbicide Leaching
2005
Stoddard, C. S. | Grove, J. H. | Coyne, M. S. | Thom, W. O.
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 μg 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 NO₃–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.
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