dumping a ton of urea on a field will indeed make the grass grow greener. There is, however, another level to this issue, namely that of micronutrients.
Apart from some fringe opinions, it’s generally accepted that the calcium, selenium, magnesium and the other
minerals plants need to grow optimally end up in the produce and have to be replaced from time to time. You can spread NPK products from here ’till doomsday without
having any effect on the levels of these substances, meaning that soil gets depleted with repeated use, particularly when only a single kind of crop is planted year after year.
This means that prime, virgin farmland will show massively improved yields the first few years after chemical fertilization is introduced, but these will eventually
decline unless remedial action is taken. In fact, much of the work being done on GMOs is intended to counteract this trend, for instance by creating plants that can
utilize soil nutrition without the presence of humic acids.
Turning to Poop
Even today, the compacted manure feedlots produced is often simply stockpiled in giant pyramids. These often produce methane in such quantities that some piles catch
fire and burn for several months.
This is a terrible waste of a practically free natural resource. Even without composting, manure of all kinds comprises great fertilizer which not only boosts headline
NPK figures, but also replenishes micronutrients and improves soil structure. Intensive animal-rearing facilities will often be happy for anyone to collect their waste
at own cost, as manure management makes up a huge part of their running costs.
Transport and Handling
Clearly, there’s a huge difference between handling dry dung and slurry. In fact, if the manure is intended for use as fertilizer, it’s recommended to stay away from
liquid manure altogether, particularly that from hog farms.
Dry waste, by contrast, presents very little in the way of health hazards to workers and doesn’t smell (much). Ordinary face masks should be sufficient to guard
against the irritation caused by dust inhalation. Animal waste may indeed contain parasites and pathogens capable of infecting livestock, though, so equipment and
vehicles should be thoroughly cleaned after transporting manure. The easiest way to do this is with a portable pressure washer, the kind you will find at websites like
Storage
Both environmental rules and common sense dictate that runoff should be minimized when rain is a possibility. Water running through stockpiled manure leaches out
valuable nutrients which end up polluting water supplies, so manure piles should be built on compacted and sealed terrain, as well as being covered if possible. If
using an enclosed structure to store poultry manure, bear in mind that the presence of even a little moisture will cause ammonia gas to be released, which is not only
noxious but can start fires.
Spreading Manure
Manure from off-site is not an ideal way to fertilize pasture, as this may introduce foreign pathogens if not composted first. For crops, though, it can be used
directly without concern.
Manure is typically spread a few weeks before planting to allow some time fot it to degrade, and never within 190 days of harvest. When spreading, precipitation is the
main concern. Heavy rains and steep slopes will contribute to nutrients being washed away into water sources without your plants ever benefiting from them.