Effects of Surface‐Applied Limestone on the Efficiency of Urea‐Containing Nitrogen Sources for No‐Till Corn

Abstract

AbstractFertilizer 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.