How much vapor does an
inject into the soil???
The real question is: how much is retained by the soil? An anhydrous applicator injects the percentage of vapor determined by the temperature/pressure in the nurse tank. But the amount retained is a function of the tillage used to disturb the soil. Whether the ammonia exits an orifice at the bottom of an opener/knife or from a steel tube, it is a mixture of liquid and vapor. When liquid ammonia is at atmospheric
pressure it assumes the equilibrium temperature of -28°F (see chart below).
As you can see from the chart, when anhydrous NH3 in a cold tank at 30°F flows to atmosphere, it is about 10% vapor by weight. However, the vapor is about 98% by volume. If you apply 200 lbs of N at 7 mph, this is 0.143 lbs of NH3 per row per second. The resulting vapor is .25 cu ft (2 gallons) per sec, enough to fill a kid’s balloon. Porous soil adsorbs liquid ammonia readily on contact. Soil contact with ammonia vapor is more of a problem. With a large volume of vapor and a small surface area of soil, vapor tends to go to the air.
Higher temperatures are worse for vapor. 80°F results in 20% vapor by weight, 99.5% by volume. The vapor volume is then over 4 gallons per second.
The gold standard for trapping anhydrous has been the “mole knife” made by Hi-Pro in Watseka, IL. But the mole knives require a lot of HP and disturb the soil too, much for some situations. Bourgault mid row banders are used extensively in the North and West. They incorporate vapor but not as well as some farmers desire. John Deere has mid row banders on their planters and seeders but these, too, are not universally satisfactory. Sweeps and chisel plows often do an adequate job but also disturb the soil with their tillage. The trick is to use less tillage with greater efficiency. Not all tillage is useful to incorporate NH3.
We believe we are very knowledgeable in the best way to get anhydrous from the tank to the injection location. But we have no expertise on injection methods. The world may be waiting for a better injection method. We constantly look at the new approaches. Here are a couple which have caught our eye:
EQUAPLY® systems offer three main advantages for ammonia applicators.
- Most important is row to row equality. Extra N need not be applied as insurance against a bad row. With anhydrous now about $800 per ton, a 10% saving is significant.
- The centrifugal pump allows full speed even with a cold nurse tank.
- Our knife pressure gage option lets you know if you have a plugged row.
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