Organic materials can be broadcast on the surface and tilled or watered into soil, or applied in a narrow band on or beneath the surface. A common fertilizer spreader will often work well for applying small quantities of organic fertilizer. Rotary spreaders may broadcast organic materials in a 5 to 10 foot wide path but with less uniformity and rate control than drop spreaders. Many organic materials contain high levels of salts. These salts will burn plants if organic materials are overapplied.
Spreaders are adjustable for different fertilizer materials and rates of application.
The spreader manufacturer will list calibration settings for various inorganic fertilizers. The gardener must calibrate these spreaders for organic fertilizer materials. Adjust the spreader to a relatively high setting. Place two or three pounds of organic material in the hopper and proceed to spread this amount in a continuous straight path. Note the width of the spread path and the distance traveled to broadcast all of the material.