There is a lot of uncertainty as to how much anhydrous can be injected with the currently available openers and knives. Application rates go from 30 lb. of N per acre at 4 mph for wheat to 280 lb. of N at 10 mph for corn on corn.

We believe that "mole" knives made by Hi-Pro Mfg. of Watseka, Illinois can incorporate the highest rates. But many farmers can't use mole knives, either because of the horsepower requirement or because of soil disturbance. Various mid row banders and disk openers can be used, but they are probably not as effective as "mole" knives at the highest rates. Dawn Equipment and Yetter have some new designs which are worth considering. The trick is incorporate as much of the vapor as possible since vapor tends to blow away. The correct method of tillage at the opener is key. While not all types of tillage are beneficial to incorporation, some are superior to others. The devil is knowing which is which.

There are a myriad of choices available including attachments to seeders and planters. While we can't quantify the differences, it is generally true that the more aggressive the tool, the more anhydrous it can incorporate. Intuition suggests that soil particles must be vigorously mixed with soil particles to cause vapor to be adsorbed . Also, if you apply when planting, you must keep anhydrous away from the seed.

While we don't give advice on tool selection, we provide even flow among those injectors you select. Install the injector and we'll get anhydrous to it, evenly, and at the desired rate.

We are often asked about the effect of placing orifices at the ends of knives. There has been some misunderstanding about what happens at these orifices. Some believe that this orifice location creates a high velocity stream of liquid anhydrous at the exit of the orifice.

Actually, the stream inside the orifice just before the exit is probably all liquid. However, the instant the liquid exits the orifice it becomes a mixture of liquid and gas. The reason for this is that anhydrous explosively boils at the new lower (atmospheric) pressure as it can cools to a new saturation temperature of -28°F. For example, the temperature of the anhydrous in the nurse tank may be 50°F at a pressure of 75 psig. As anhydrous exits the orifice, it is no longer under 75 psig pressure, assuming a new equilibrium condition of atmospheric pressure, resulting in a temperature of -28°F. The stream of anhydrous exiting the orifice is from 10% to 20% gas, dependent on the temperature in the nurse tank.

Even at small pressure drops, the volume of vapor dwarfs the liquid volume. TO SEE A DISCUSSION AND GRAPH ABOUT RELATIVE VAPOR AND LIQUID VOLUMES CLICK HERE.

There is a lot of discussion as to whether the stream of anhydrous liquid and gas can cut into the ground. This may depend on the soil and soil moisture. It is highly unlikely that the typical rates for anhydrous do much cutting.

One possible problem with bottom mounted orifices is the velocity of the vapor portion of the anhydrous stream exiting a very small orifice. Since velocity increases with decreasing exit hole size, tiny orifices impart a very high velocity. This may be enough to cause the vapor to "bounce" at the point of impact.

In a 1962 Douglas Johnston patent, assigned to John Blue Company, pressures of over 3000 psig were used to obtain exit fluid velocities above 700 feet per second. The patented device probably did cut a groove and inject anhydrous into the soil at these conditions. However, no current pumped system (including Equaply® units) operates at anywhere near this pressure.

One other problem with having orifices at the ends of the injectors is the elimination of a pressure difference to measure flow through individual lines. For gauges to sense flow, the pressure after the orifice must be considerably greater than atmospheric.