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Effects of surface-applied limestone on the efficiency of urea-containing nitrogen sources for no-till corn

Howard, D.D., Essington, M.E.
Agronomy journal 1998 v.90 no.4 pp. 523-528
Zea mays, urea, urea ammonium nitrate, no-tillage, limestone, soil injection, field experimentation, Triticum aestivum, cover crops, crop yield, nitrogen content, volatilization, silt loam soils, silty soils, application rate, ammonium nitrate, Tennessee
Fertilizer N and lime amendments are commonly surface-applied to no-till (NT) production systems, but research on these practices under NT is limited. We examined the effect of surface-applied limestone on the efficiency of urea, urea-NH4NO3 (UAN), and NH4NO3 applied broadcast or injected for NT corn (Zea mays L.) production on loessal soils. No-till field studies were established on two loessal soils in western Tennessee: a Memphis silt loam (fine-silty, mixed, active, thermic Typic Hapludalf) that had been in NT for 7 yr and a Collins silt (coarse-silty, mixed, acid, thermic Aquic Udifluvent) that had been under conventional tillage. Corn, with a wheat (Triticum aestivum L.) cover, was established on the Memphis soil in 1990. In 1994, corn was established on the Collins soil. The experimental design was a randomized complete block with a split-plot arrangement of treatments. Agricultural limestone was surface-applied at rates of 0 and 1.12 Mg ha(-1), 1 to 3 wk before N treatment. The N treatments were UAN broadcast (UAN-B), UAN injected (UAN-I), urea broadcast or split-applied (Urea-B and Urea-S), and NH4NO3 broadcast (AN-B). Nitrogen treatments were applied at 168 kg ha(-1) within 5 d after planting. For the split urea treatment, 84 kg ha(-1) N was broadcast at planting and 84 kg ha(-1) N was surface-banded at the 8-leaf growth stage. Applications of AN-B, UAN-B, and Urea-B resulted in lower grain yields and leaf N concentrations than UAN-I. These reductions were attributed to N immobilization and NH3 volatilization. Average yield reductions attributed to N immobilization were 8% on the Memphis soil and none on the Collins soil. Volatilization losses attributed to UAN-B were 8 and 12% for the Memphis and Collins soils, respectively. Yield reductions attributed to NH3 volatilization from Urea-B were 22 and 19% for the Memphis and Collins soils. Splitting the urea application increased yields relative to the Urea-B treatment only on the Memphis soil. Surface application of limestone decreased Urea-B yields.