Submitted to: Extension Publications
Publication Type: Experiment Station
Publication Acceptance Date: March 1, 1998
Publication Date: N/A
Technical Abstract: Nearly anyone who has spent time growing a crop of corn has witnessed variability of its yield within a field, which has become much more obvious with the advent of precision farming technologies. We have witnessed similar occurrences while conducting a watershed scale N management and water quality research project. Every cornfield in the study area included an N deficient rate strip (50 lb. N/ac), a well fertilized, nonlimiting N rate strip (250 lb. N/ac) and the remaining area had an N rate based on the late-spring soil nitrate test (LSNT). The 50 lb. N/ac rate had significantly lower yields on the hilltop and sideslope soils than the other N rates and had mixed results in the lowland soils. The LSNT rate yields were similar to the nonlimiting rate on the lowland and sideslope soils, but greater on the hilltop soils. We can then accept that the LSNT rate optimized corn yield. Also, it appears that the 50 lb. N/ac rate may have been a sufficient N rate to optimize yields on the lowland soils. Had we based our method of LSNT sampling on the results of this first year of data we would have grouped sample sites by topographic location. The lowland soils would have been sampled independently of the sideslope/hilltop soils. Assuming we applied 50 lb. N/ac for the lowland soils and 157 lb. N/ac (LSNT rate for this field) for the sideslope/hilltop soils, how much would have been saved in production costs? With the lowland soils comprising 16 acres of this field and side slope/hilltop soils 61 acres, 1712 less lbs. N would have been applied. At 12 cents per lb. N, this would have saved $205.44 in production costs, or $3.06/ac. The environment may have had even greater savings.