NITRATE LOSSES TO TILE DRAINAGE AS AFFECTED BY NITROGEN FERTILIZATION OF CORN IN A CORN-SOYBEAN ROTATION

Document
Description
A study, initiated in 2000 and continued in 2004, was conducted to determine the influence of rate and time of N application and the nitrification inhibitor, N-Serve, on the yield and uptake of N by corn and the loss of NO3 to tile drainage. Anhydrous ammonia (AA) was applied on October 30, 2003 at rates of 0, 80, 120, and 160 lb N/A and on April 15, 2003 at 120 lb N/A. The anhydrous ammonia applicator malfunctioned sometime during application of the fall N treatments, and we were not able to determine what rates of N were actually applied. Thus, all corn production and tile drainage nitrate data associated with the fall treatments were rendered useless and are not reported. Although the corn grain yield difference between the spring-applied N with N-Serve (219 bu/A) and without N-Serve (204 bu/A) treatments was only statistically significant at the 85% level, the spring-applied N-Serve did return about $20/A. Recovery of N in the above-ground plant dry matter was greater when N-Serve was added to spring-applied N (62%) compared to excluding N-Serve (53%). Nitrogen uptake from the fertilized grass plots (19 lb/A) amounted to only 11% of the amount of fertilizer N applied (174 lb N/A). Tile lines flowed for a total of 70 days during the period from May 20 through October 16. Total drain flow from the soybean and grass plots averaged 18.12" and 14.34", respectively. For the season, flow-weighted nitrate-N concentrations from the soybeans averaged 8.9, 12.2, and 20.0 mg/L for the 80, 120, and 160-lb N rates with N-Serve, respectively, applied for the 2003 corn crop. Nitrate-N loads in the tile water for the year totaled 37, 53, and 84 lb/A for the 80, 120, and 160-lb N rates, respectively. Thus, considerable N carried over from 2003 and was lost in drainage from soybeans in 2004. Nitrate-N concentrations for the grass plots averaged 5.4 mg/L and loads totaled 20 lb/A – the equivalent of 11% of the fertilizer N applied to those plots in 2004. Normalized for tile flow, NO3-N losses per inch of drainage from the soybeans averaged 0.46, 0.64, and 1.13 lb/A/in. for the 80, 120, and 160-lb N rates, respectively, applied for corn and 0.38 lb/A/in. for the grass plots. Compared to the recommended 120-lb N rate, NO3-N losses were reduced 28% by cutting the N rate back to 80 lb/A but were increased 77% by increasing the N rate to 160 lb/A. Soil NO3-N and NH4-N data from the AA bands indicated significant nitrification of the fall-applied AA by early May. Spring-applied (April 28) AA had nitrified almost completely by June 7 when N-Serve was not used, but when used NH4-N was still present in significant amounts on June 7. Nitrogen (N) losses to tile drainage water have been directly linked to N additions
Date Issued
2004
Number of Pages
8
Decade
Main Topic
Rights Holder
Minnesota Water Research Digital Library
Rights Management
Public Domain