Estimating Economically Optimum N Rates from On-Farm Demonstrations. (A08-mulla199442-oral)
Authors:
J.A. Hernandez - Univ. Minnesota D.J. Mulla* - Univ. Minnesota
Abstract:
This research was conducted on corn fields using landscape scale experiments to 1) estimate the economically optimum nitrogen rate (EONR) and 2) estimate the yield of corn at the EONR. Fertilizer nitrogen (N) was applied at different rates during the fall of 2001 in long (over 450 m), wide (over 60 m) strips crossing the landscape on 29 fields in southern Minnesota. The rates applied were 67, 101, 134, 168, and 202 kg/ha, with control strips on seven of the fields. Corn yield was measured at harvest using calibrated yield monitors operated by the farmer. Results showed that the EONR for all fields studied averaged 116 kg/ha, with a corresponding yield at EONR of 11.6 Mg/ha. The rate of fertilizer N recommended for these fields using University of Minnesota guidelines was 134 kg/ha. EONR ranged from 22 to 202 kg/ha, with about 15% of the fields having an EONR greater than 157 kg/ha.
EONR values for soils within farms averaged 118 kg/ha, with a range of from 11 to 217 kg/ha. Less than 15% of the soil series studied had EONR values greater than 157 kg/ha. EONR increased linearly with yield for the Clarion, Nicollet, and Webster soil series. This suggests that by measuring crop yield goals for these soil series, one could estimate EONR using linear regression. On average, these results show that even during the best crop yielding years, farmers could apply University recommended rates of N fertilizer without reductions in corn yield on 85-90% of all soil types.
Speaker Information: D. J. Mulla, Univ. Minnesota, Dept. Soil, Water and Climate, St. Paul, MN 55108;
Phone: 612-625-6721; E-mail: [email protected]
Session Information: Tuesday, November 4, 2003, 12:55 PM-5:55 PM Presentation Start: 3:15 PM
Keywords: N fertilizer; Variable rate N application; Economically optimum N rate; N rate by soil type