Maize yield and nitrogen uptake after established no-tillage fields are plowed

Information is lacking concerning the effect of spring plowing (CT) an established (5 years or more) no-tillage (NT) field on maize (Zea mays L.) grain yield and nitrogen (N) uptake. A 3-year split plot field experiment, with two levels of tillage (CT and NT) and six levels of fertilizer N (0-336 kg N ha^-1 as NH₄NO₃), was conducted on a Coshocton silt loam soil (fine, loamy, mixed, mesic Aquultic Hapludalf) maintained in NT production for 5 previous years. Each year a new area of the established NT field was plowed and treatments were repeated for 2 consecutive years on the same plots. Carryover of N and lack of mineralization of organic N resulted in maize grain yields and N uptake being similar under NT and CT across all N fertilizer rates for the first crop following spring plowing. However, for the second crop after plowing, grain yields and N uptake were higher at the zero or low N fertilizer rates under CT as compared with NT and the reverse was true at the high fertilizer N rates. Addition of a small amount of N (56 or 112 kg ha^-1) stimulated organic matter decomposition and/or N immobilization primarily during the second year after plowing. Nitrogen concentrations in the grain and residue were less for the NT compared with the CT treatment although yields of grain and residue were generally greater under NT. The greater efficiency of maize plants under NT in utilizing N taken up from the soil to produce grain was attributed to the greater amount of water in the soil during the growing season.