Dribbling N solutions through drop tubes or hoses is a practice which may be advantageous to many farmers. It can increase the speed of sidedressing, a practice which can increase N efficiency on more poorly drained soils. It also allows farmers to use N solutions safely for no-tillage corn production, either early in the season or as a sidedressing. This is a fairly easy practice to accomplish and equipment modifications are generally inexpensive.
Dribbled applications can be made before planting, at planting, immediately after planting, or as a sidedressing after corn emerges. For applications before planting, hose spacings of 30" or less will reduce chances of salt injury if seed rows cross fertilizer bands. Planter attachments can be mounted to feed each row individually (approximately 6" from row) or such that one band feeds two rows (60" hose spacing in row middles for 30" seed row width). For applications after emergence, particularly delayed sidedressing, it is probably advantageous to band N 6-10" from each row.
There is little evidence currently available to indicate the best time for sidedressing in Ohio, but the good chance for dry weather in July and August dictates that sidedressing should not be delayed past early June if possible. Surface applied N must have enough rain to move it down into the root zone for uptake. The most important factor in sidedress timing is to begin at a time which will ensure that the entire acreage can be fertilized. Any sidedressing program should include 25-50 lb N/A at planting, to nourish the crop until the bulk of N is applied.
Most farmers and custom applicators can modify existing sprayers to accomplish dribble applications at a reasonable cost. Extra nozzle bodies should be mounted on the boom, if necessary, to provide proper hose spacing. Spray tips or precision metering orifices can be used to control flow at each nozzle body and it is recommended that corrosion resistant materials be used to maintain calibration. A hose or drop tube is then attached to the nozzle bodies, either slipped over the body itself if spray tips are used, or over a hose adapter if orifices are used. This equipment is readily available from spray equipment dealers and catalogues.
Drop tubes or hoses should be long enough to prevent splashing solutions on leaves and causing tissue damage. On flat fields, discharging material an inch or so above the ground is acceptable. On slopes where constant boom height cannot be maintained, limp hoses, with several dragging inches on the ground, may increase the margin of safety.
Calibrating a dribble applicator is identical to calibrating a sprayer. Rate of delivery will be determined by pressure, nozzle or orifice size, and tractor speed. The following calibration guide assumes constant pressure and metering. Actual rate will be determined by tractor speed.
EXAMPLE: A boom set to feed 8-30" rows delivers 13 gallons of 28% UAN per minute. If the desired rate of application is 60 gallons per acre, what is the speed of travel?
8 rows x 2.5 ft./row = 20 ft. width of coverage
Speed = (495 x 13) divided by (60 x 20) = 5.4 MPH
NOTE: Nitrogen solutions flow more slowly than water, which will affect output. If calibrating with water, but fertilizing with an N solution, multiply discharge by the appropriate correction factor. For 28% UAN, the correction factor is approximately 0.9.
Prepared by:
Donald J. Eckert
Professor, Natural Resources
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