Animal manures were the first form of
fertilizers used by humankind. People were aware of its benefits to
plant life eons ago but, in recent times, it has taken a secondary role
to commercially produced granular fertilizers. The main reason for this,
of course, was the ease of handling of granular products. There is no
odor problem and no livestock is needed to generate it.
Anyway, animal manures may still be
useful in the home landscape but not as a fertilizer. Most manures
contain only small percentages of nutrients needed by plants. So, there
main benefit is that of a soil conditioner. Composted manures will
improve both fine textured clay soils and coarse textured sands. They
improve the aeration in the soil by encouraging earthworms and
beneficial microbes that decay the
manure.
There is also evidence that the
phosphorus that is in the manure is in a form that is more easily
available to plants. In clay soils, phosphorus is bound tightly to the
soil particles and may be unavailable. Adding manure to such soils can
improve this situation.