Kevin
Yes, the equipment exists to inject manure into the soil. The two principal types are tank type injectors and towed-hose injectors.
With a tank type, a tank carries the manure from the storage tank to the field, and then traverses the field until empty. The advantage is it's ready to go now, and can be used with minimal set-up. Some disadvantages are soil compaction from a heavy tank, and long cycle times. Depending on transport times, actual application time may be only 10% of the cycle.
With a towed-hose injector, an injector is fed with an umbilical hose that is pulled thru the field by a large tractor while the waste is pumped thru the hose. The advantage is speed of application. A typical set would cover 20 acres, and would take 6 to 12 hours of continuous pumping. The disadvantage is set-up time. Pumping 3/4 mile might require one to two days for set-up and tear-down, depending on whether pipe or hose is used for transport. Unless about 250,000 gallons of waste are available, a tank would be faster.
A third common method of waste disposal involves spraying the liquid manure with a "big gun" sprinkler. Think of a yard sprinkler with a 1 to 2 inch discharge hole, operating at 100 to 200 psi. The set-up is the same as a towed-hose, but an extra operator and large tractor is not necessary. The advantage is the lowest cost disposal of large amounts of waste. The disadvantages include smell and loss of nitrogen from aqueous ammonia.
The soil tolerance to manure is quite high. Manure is an excellent fertilizer. The two drawbacks to manure as a fertilizer are concentration and nutrient balance.
The manure as a fertilizer is very diluted. The most important fertilizer for cereal and feed grains is nitrogen. Commercial fertilizers include anhydrous ammonia at 82% nitrogen, dry granular urea at 46%, or liquid UAN at either 28% or 32%. Compare this to manure at .05% to .2% nitrogen. Compounding this problem, manure is stored outside, where it is diluted further with rainwater.
Manure also contains 2 to 3 times the phosphorus necessary for a unit of grain production when applied to the soil at the correct nitrogen level. This is not a problem for infrequent application, as the soil has a high capacity to store phosphorus and phosphorus is not generally subject to leaching. This does become a problem, however, when frequent applications are made. This is often the case for the fields closest to the manure. The problem is further compounded in some instances by decades of application.
Typical application amounts for hog manure would be 3,000 to 20,000 gallons per acre, or in amounts of 1/10 to 8/10 inch.