Yield response to N fertilizer and N fertilizer use efficiency in no‐tillage and plow‐tillage corn

Yield, and N uptake response to several rates of ? fertilizer applied to non‐tilled (NT) and plow‐tilled (PT) corn were compared for 3 years in an experiment conducted on Hagerstown silt loam (Typic hapludult, fine‐loamy, mixed, mesic) in central Pennsylvania. Insufficient moisture limited yields two of the three years of the study. The 3‐year average grain yields were significantly lower with NT than with PT at the 0 kg/ha broadcast N rate and higher with NT than PT at the upper two rates (150 and 200 kg broadcast N/ha). In the year when moisture did not limit yield potential, yields with NT were lower than with PT at the 0 kg/ha broadcast ? rate, but maximum yields were equal with both tillages. It was speculated that the greater maximum yields with NT in the drier years were due to the greater soil moisture availability with NT. Analysis of the 3‐year average quadratic‐linear plateau yield response to ? fertilizer rate functions for the two tillage systems indicated that the economic optimum ? rates were 140 and 164 kg N/ha for grain yields of 8.53 and 9.05 Mg/ha for PT and NT, respectively. The effect of tillage on ? fertilizer use efficiency depended on the definition of efficiency used, but differences in efficiency between the two tillage systems were not large with either definition.