Abstract

Environmental concerns relative to nitrogen applications in grain crop production systems have become increasingly important.  Recommendations are based on projected yield potentials (yield goals) and estimated economic returns.  Various sources of nitrogen are available to farmers in wheat production systems, however, few have ever been evaluated over a long period of time.   that required for maximum yield.

Materials and Methods

In the fall of 2002, Experiment 601 was established under conventional tillage on a ________Grant silt loam (fine-silty, mixed, thermic Udic Argiustoll).  For 28 years, wheat has been planted in 10 inch rows in this North Central Research Station experiment.  The experimental design employed is a randomized complete block with four replications.  Variety changes and associated fertilizer application, planting and harvest dates are included in Table 1.  Fertilizer treatments used in this experiment are defined in Table 2.  The sources of nitrogen

Table 1.  Treatment  applications, and experimental management  for continuous winter wheat Experiment 505, Lahoma, OK, 1971-2000.