Agriculture Reference
In-Depth Information
TABLE 18.4
Major Plant Nutrient Elements in Earthworm-Processed
Animal Waste
Element Content (% dry weight)
Waste Material
N
P
K
Ca
Mg
Mn
Separated cattle solids
2.20
0.40
0.90
1.20
0.25
0.02
Separated pig solids
2.60
1.70
1.40
3.40
0.55
0.03
Cattle solids on straw
2.50
0.50
2.50
1.55
0.30
0.05
Pig solids on straw
3.00
1.60
2.40
4.00
0.60
0.05
Duck solids on straw
2.60
2.90
1.70
9.50
1.00
0.10
Chicken solids on shavings
1.80
2.70
2.10
4.80
0.70
0.08
Commercial plant growth medium
1.80
0.21
0.48
0.94
2.20
0.92
spent mushroom compost, all contain straw, which takes considerably longer for the earthworms
to fragment than the more particulate materials, such as separated animal solids and slurries, brewery
wastes, paper pulp, and similar materials. However, the final product from most organic wastes is
usually a finely divided, well-stabilized and humified, peatlike material with excellent structure,
porosity, aeration, drainage, and moisture-holding capacity and a low C:N ratio (Edwards 1983).
Structurally, it has the appearance and many of the characteristics of peat and contains plant nutrients
usually in adequate amounts for plant growth.
The chemical nutrient contents of vermicomposts differ greatly, depending on the parent
material from which they are processed. However, when their nutrient content is compared with
that of a commercial plant growth medium, if they are processed from animal wastes, they
usually contain most of the necessary mineral elements for plants, although there may sometimes
be a deficiency of magnesium, which can be remedied by addition of magnesium sulfate (Table
18.4). An important feature of vermicomposts is that, during the processing of the various
organic wastes by earthworms, many of the nutrients that they contain are changed to forms
that are more readily taken up by plants, such as nitrate or ammonium nitrogen, exchangeable
phosphorus, and soluble potassium, calcium, and magnesium (Table 18.5). Moreover, many
TABLE 18.5
Effect of Earthworm Activity on Nutrients in Organic Wastes
Exchangeable (% d.m.)
Nitrate Nitrogen
Readily Soluble P
Organic Waste
(ppm)
(% d.m.)
K
Ca
Mg
Cattle waste
Unworked
8.8
0.11
0.19
0.35
0.05
Worm worked
259.4
0.18
0.41
0.59
0.08
Pig waste
Unworked
31.6
1.05
1.49
1.56
0.45
Worm worked
110.3
1.64
1.76
2.27
0.72
Potato waste
Unworked
74.6
0.19
1.94
0.91
0.24
Worm worked
1428.0
0.22
3.09
1.37
0.34
d.m., dry matter.
