Incorporating stall material into the soil can reduce use of inorganic fertilizers.
Inorganic fertilizers (man made), which contain readily available nutrients and little to no organic matter (OM), are commonly used to maintain soil fertility in pastures. Unprocessed (non-composted) organic materials, such as horse manure, while high in OM, may not contain nutrients in the readily available state. Land application of composted horse manure represents a management strategy that could replenish soil OM, and reduce the need for inorganic fertilizer.
The objective of this study conducted at the University of Florida was to evaluate soil and forage characteristics in response to fertilization with inorganic fertilizer, unprocessed stall materials or composted horse manure that has been introduced by soil incorporation (tillage) at the time of pasture establishment.
Incorporation of horse stall material into soil, whether unprocessed or composted, produced similar forage yield to that observed with inorganic fertilizer in newly established pasture. Soil OM was not impacted by any of the fertilizers. An increase in soil OM may require more than one yearly application of compost, particularly on sandy soils.
The results of this study suggest that the incorporation of unprocessed or composted horse stall materials into soil can reduce or replace the use of inorganic fertilizers when establishing grass pastures with minimal reduction in forage quality or production. Such a practice could decrease the cost of manure disposal and purchased inorganic fertilizer, recycle nutrients, and reduce environmental degradation by stabilizing nutrients that may threaten water quality.
Spreading horse manure (whether composted or not) on an existing pasture has different guidelines than above. If you have less than one horse for every two acres of pastures, you may be able to spread additional manure on the pasture without increasing the parasite load. If you have more than one horse for every two acres of pasture, then spreading additional manure is not recommended.