Improved N application methods and N sources for corn in Southwestern Ontario

Introduction:
Increased farm sizes have resulted in greater time constraints for producers to apply nitrogen fertilizers to crops. Hence, some producers have now started applying their N by either streaming UAN onto their soils or are considering adding inhibitors with urea or UAN to reduce losses of applied N. The increased use of urea and UAN fertilizers compared to other N sources may also enhance N losses through ammonia volatilization and/or denitrification (nitrous oxide and dinitrogen emissions).

In 2014, an AAFC A-Base project has been secured to examine ammonia volatilization losses from soils using wind tunnels. Bridge funding is requested to expand the analysis and examine the fate of applied N in soils by measuring ammonia volatilization, nitrate leaching and nitrous oxide emissions. In addition, plant N uptake will be measured during the growing season from 10 treatments including 3 different application methods, 3 different N sources and a unfertilized control.

Materials and Methods:
The study site is located at Eugene F. Whalen Experimental farm, in Woodslee, Ontario on a Brookston clay loam soil. This is the dominant soil type in southwestern Ontario. Corn will be planted when the soil is fit and a pre-plant application of starter fertilizer will be banded 5 em beside and 5 em below the seed. The starter fertilizer will contain 20 kg N ha^-1. An additional 130 kgN ha^-1 will be applied to the corn as a side-dress application when the corn is at the 6-8 leaf stage. The side-dress N treatments will involve a 3 by 3 factorial combination of different methods of application (broadcast, banded, streamed) and different N additives (control, urease inhibitor, or a urease and a nitrification inhibitor). An unfertilized control treatment will be included in the main trial for a total of 10 treatments. In addition to the above main trial, we will also evaluate 5 N rates (0, 50, 100, 150 and 200 kg N ha^-1) using ammonium nitrate will enable us to determine the N response curve for corn.

Wind tunnels will be placed on 18 plots (6 treatments at 3 reps) and ammonia volatilization losses will be measured every day for 28 days. Chambers will be installed on each plot and nitrous oxide emissions will be determined on a weekly basis for the growing season. Soil and plant samples will be collected every 3 weeks for total N content in the above-ground portion of the crop and for the inorganic N concentrations in the top 30 em of soil. Final harvest and both grain yields and above ground biomass samples will be determined. Soil cores will also be collected after harvest to determine the extent of nitrate movement through then soil profile.

Goals and Deliverables:
The primary goal is to identify the management systems and fertilizer additives which will enhance crop growth and nutrient uptake while reducing ammonia volatilization losses, nitrous oxide emission losses and leaching losses. The proposed study will enable us to derive an N budget for corn in SW Ontario. Improved understanding of the fate of applied N will help producers improve nutrient efficiencies and ultimately match their N application rates to crop demand to optimize profit while improving environmental quality.