Many home gardeners want to grow fruits and vegetables with organic sources of fertilizer. Considering the many benefits of the addition of organic materials, this subject warrants attention. Manure and composted plant materials add organic matter, which aids in moisture retention, helps reduce compaction and can buffer extremes in pH. It also helps maintain the structure and nutrient holding capacity of the soil.

However, the nutrient level of organic materials is lower, rate of release is slower and levels of minerals may vary and are not balanced. The information below will help you interpret differences in nutrient content and relative availability of organic materials.

Fruits and vegetables often have high nitrogen demands, and it can be difficult to provide sufficient nitrogen from an organic source throughout the growing season of the crop. In addition, availability of nitrogen late in the season can make perennial plants such as raspberries and apples susceptible to winter injury. It is a challenge to provide plants with a readily available organic nitrogen source early in the growing season, yet have it less available in late summer.

Much variability exists in the composition of similar organic materials. For example, manure with straw will have a different nitrogen composition than pure manure, and the rate of nitrogen release may be slower because of the higher amount of carbon in the straw. The table below lists the approximate composition of various organic materials, and the nitrogen, potassium and phosphorus that can be provided from them.

Composition of Manure
(from Samples Reported in Knott's Handbook for Vegetable Growers)
  Moisture (%) Nitrogen Phosphorus Potassium
Fresh Manure with Bedding or Litter
Cattle 86 11 4 10
Duck 61 22 29 10
Goose 67 22 11 10
Hen 73 22 22 10
Hog 87 11 6 9
Horse 80 13 5 13
Sheep 70 20 15 21
Turkey 74 26 14 10
Dried Commercial Products
Cattle 10 42 42 61
Hen 13 31 31 40
Hog 10 45 45 20
Rabbit 16 26 26 32
Sheep 16 32 32 41
From: Lorenz, Oscar A. and Donald N. Maynard, 1980
Knott's Handbook for Vegetable Growers. Second edition, pg. 76

 

Guide to the Mineral Nutrient Value of Organic Materials (%)
Materials Nitrogen Phosphorus Potassium Relative Nutrient Availablity
Bone Meal (raw) 2 to 6 15 to 27 0 Slow
Bone Meal (steamed) 0.7 to 4 10 to 34 0 Slow Med.
Cocoa Shell Meal 2.5 1 2.5 Slow
Compost (not fortified) 1.5 to 3.5 0.5 to 1 1 to 2 Slow
Cotton Seed meal (dry) 6 2.5 1.7 Slow Med.
Dried Blood (dry) 12 1.5 0.57 Med. Rapid
Fish Meal (dry) 10 4 0 Slow
Manure (fresh)        
Cattle
 0.25 0.15 0.25 Medium
Horse
 0.3 0.15 0.25 Medium
Sheep
 0.6 0.33 0.75 Medium
Swine
 0.3 0.3 0.3 Medium
Poultry
(50% water)
 2 2 1 Med. Rapid
Milogranite (dry) 5 2 to 5 2 Medium
Mushroom Compost 0.4 to 0.7 1 0.5 to 1.5 Slow
Peat and Muck 1.5 to 3 0.25 to 0.5 0.5 to 1 Very Slow
Sawdust 4 2 4 Very Slow
Sewage Sludge (digested) 1 to 3 0.5 to 4 0 to 0.5 Slow
Urea 42 to 45 0 0 Rapid
Wood Ashes
(may raise pH)		 0 1 to 2 3 to 7 Rapid

 

Resource: A Guide to the Nutrient Value of Organic Materials, Fact Sheet #8, by Marcia Eames-Sheavly Extension Support Specialist, Department of Fruit and Vegetable Science, Cornell University and Robert Kozlowski and Joann Gruttadaurio, Senior Extension Associates, Department of Floriculture and Ornamental Horticulture, Cornell University, Spring 1993.