The application of organic fertilizers does not need to be as precise as the application of inorganic fertilizers. Most organic fertilizers release their nutrients slowly, over time, so there is little chance of scorching your plants.
Giving precise instructions on how much fertilizer is impossible because this will depend on soil, the weather and the plants you want to grow.
Granular and Powder fertilizers should always be used to provide general nutrients as a supplement and compost should always be used when preparing garden soils for planting.
The application of granular and powdered fertilizers are normally recommended in pounds per square foot or yard. Keep fertilizer off foliage (unless a diluted tea has been prepared). Follow application rates on package of each type of fertilizer. As a general rule when no application rate is available, use 5 lbs. per 100 square foot. Of course many fertilizers can be applied at a higher rate, but when in doubt less is more.
There are several ways granular and powdered fertilizer can be applied. On our beds we amend with plenty of compost at the beginning of the planting season, work in, smooth out and sprinkle fertilizers over the surface and lightly work into the top 2″ of soil. This can be done quickly with a rake for larger areas or with a hand cultivar on small raised beds. As an example of what we do and use in a 3′ x 30′ bed; Clear garden beds, top with 6″ of well rotted compost, till or spade to the depth of 12″, rake surface flat, sprinkle 5 lbs. Bloodmeal (3-5 lbs more for leafy greens) 7 lbs. Bonemeal (or 10 lbs calphos), 5 lbs. Greensand, evenly over entire worked surface, quickly work into the top surface, let soil settle for a day or two. We find this to be the easiest and best method for us.
Organic fertilizers can also be sprinkled into the rows. When this is done you will need to convert the square yard to a linear one. Hoe seed rows, sprinkle fertilizers down row before seeding. We like to lightly run the hoe or a bamboo stick down the row to slightly mix the fertilizer with soil before seeding. This isn’t necessary when using organic fertilizer as it would be essential for synthetics, but find it to be best practice.
Adding Granular or Powdered fertilizer in each planting hole is also and option. We do this when summer transplants are planted later in the season when beds were prepared in earlier spring. Simply dig transplant hole add 1-2 T. (follow package recommendations), lightly mix with soil in hole, plant transplant and fill in hole. By doing this, you are providing nutrients right at the root zone to get them off to a great start. For leafy greens we use a higher nitrogen fertilizer while plants such as peppers, we use a high phosphorus fertilizer, but still containing other important nutrients. Starter Mix fertilizer is a great, well balanced fertilizer to use for any transplant.
Side dressing with organic fertilizer is done by sprinkling fertilizers along side each plant or row of plants. Either a small trench of 1″ or less is along side plants and fertilizer is sprinkled in and covered or a circle around each plant done in the same manner. Keep trench 3″ to 12″ away from stem of plants. Further away the larger the plant being careful not to disturb roots. We choose a slightly different method for side dressing with fertilizer. Simply sprinkle fertilizer around plants and cover with 1/2 -1″ of compost or soil conditioner. This provides essential fertilizers as well as amending the soil at the same time.