If an air seeder is delivering seed or solid fertilizer to the soil, it cannot be injecting the air it uses to deliver the product. The gas needs to be allowed a free escape or the seed tubes will quickly plug with solid product. The best the so called 'injectors' will do is bounce the air off the soil. Seeing that you normally plant the seeds as shallow as possible and get them in moist soil, it is not the ideal method of 'injecting' gas.

Anhydrous ammonia has a real affinity for moisture and will be drawn to damp soil. Do you know of anyone who would apply anhydrous by bouncing it off damp soil? Doing so would waste most of it. Most who apply it "here", try to get it in a deep slot and take measures to close the slot as quickly as possible so the gas has no chance to escape. As mentioned, if you try similar with an air-seeder, the tubes will plug with seed and it is a major headache to un-plug them.