Mitigating Leaf Burn: Streamer Nozzles and Dissolved Urea

28% has become the preferred nitrogen source on winter wheat in Ontario.  Application is perfectly uniform, something that seems difficult to achieve with most urea applications.  However, leaf burn is one of the main problems with 28% applications, particularly at later stages of growth.  With more emphasis on split nitrogen applications, and renewed interest in even later N applications on Hard Red Winter wheat for protein, leaf burn is becoming problematic.

Different nozzles and the resulting burn injury are being further evaluated, but all nozzles cause some burn under adverse conditions.  Boom height is a critical factor with some streamer nozzles.  3 stream and 6 stream nozzles suffer the most from variable boom height. Chafer streamer bars (often called Needham streamer bars) suffer the least from boom height variations.  In general terms, the fewer the streams, the less chance of burn. At proper boom height, differences in leaf burn are small.  Unfortunately, boom height variations can cause nozzles more affected by boom height to cause significant burn, and even “striping” in the wheat under dry conditions.

Lower N applications, or diluting the 28% with water reduces burn significantly. However, this increases the volume applied and slows the application process.  Application during a rainfall will negate burn, and sounds great in theory. Practically, however, this is not very feasible.  In Europe, dissolved urea is often used for later N applications, to reduce or eliminate burn.  Initial investigations indicate a significant reduction in leaf burn using dissolved urea.  Dissolved urea through flat fan nozzles still causes unacceptable burn: but dissolved urea through streamer nozzles causes little to no burn. At 2 lbs/US gallon of nitrogen, dissolved urea offers less burn and lower application volumes (28% is 3 lbs N/US gal) than a 1:1 blend of 28% with water.

Making Dissolved Urea:  Dissolve 4.51 pounds of urea (46-0-0) per US gallon of water to obtain 21-0-0. It takes time and really good agitation to dissolve this much urea per gallon, especially a larger batch. Start with warmer water if possible, as it is a very endothermic reaction (needs heat).  Dissolving urea in cold water is very slow. Leave the water in the tank for a few days, to allow the water to warm from the sun, rather than pulling cold water out of the ground. The easiest way to dissolve a larger batch is using a smaller tank (+/- 1000 gal) and ~5 hp 2” pump to agitate the material well. Slowly add the urea with an auger into moving water, the more circulation the better. Direct the flow of liquid down and around the bottom of the tank: once urea settles on the bottom it is hard to agitate it and dissolve it.  (Adapted from: Phil Needham , Needham Ag Technologies, LLC.)

Liquid Urea 21-0-0  Properties:

Weight per US Gallon 9.44 lbs

Specific Gravity 1.132

Pounds (N) per US Gallon 2.077

pH 6.0 – 7.2