The Scoop on Fertilizer

One of the unexpected joys of rural living is access to fertilizer. There is an abundance of animal manures in Tuolumne County available to use as soil amendments and/or fertilizers for your garden.

Why use animal manures? They act as both organic fertilizers and soil amendments. As fertilizers, manures are high in the nutrients necessary for plant growth and development. The California Master Gardener Handbook suggests that manures are more complete than inorganic fertilizers, as they provide micronutrients, as well as the macronutrients nitrogen (N), phosphorous (P) and potassium (K).

As soil amendments, manures improve the physical properties of the soil, such as increased aeration, water infiltration, moisture-holding capacity and decreased soil density. Manures also are typically a valuable source of bacteria that help to convert certain nutrients to forms that are more useable by plants.

Are there disadvantages to using animal manures in your garden? Certain types of manure, like horse manure, can contain weed seeds. Another potential problem with using animal manures can be salt content than can accumulate in poorly-drained soils. Excrement from dogs, cats and humans should never be used in gardens as they can transmit diseases.

What type of animal manure is most advantageous for a home garden? When all the factors that affect nutrient value are held constant, chicken or poultry manures contain the greatest concentration of nutrients. Rabbit, goat and sheep manures are fairly high in nitrogen (“hot” manure). Horse manure is less rich than chicken manure, but contains more nutrients than cow manure. Llama and alpaca manures are lower in nutrients (“cold” manure) but tend to be free of weed seeds, since food is digested a second time.

What is the difference between ‘cold’ and ‘hot’ manures? Cold manures release nutrients slowly and can be added directly to newly planted soil. In contrast, hot manures release nitrogen rapidly, burning plant roots and inhibiting seed formation if added directly to new plants. Seasoning (composting) cold manures as well as hot manures may be the best practice.

Kathi Joye is a Master Gardener who spends time tending her garden, as well as raising guide dog puppies for Guide Dogs for the Blind.