Chapter 8: Fertilizer & Other Soil Amendments

Fertilizer

In all forms of revegetation, applications of fertilizer at the time of seeding are necessary.  Most commercial fertilizers meet minimum standards and quality problems are seldom encountered.  If problems arise with fertilizers, as a product, they can usually be traced to the product becoming wet during storage or shipment.

Fertilizer is described by a three number designator; for example, 20-20-10. These numbers are percentages of three elements: nitrogen, phosphorus, and potassium, respectively.  Therefore, 20-20-10 fertilizer contains 20% nitrogen, 20% phosphorus, and 10% potassium by weight.

If possible, fertilizer should be applied concurrent with or prior to seeding, because once the seed has been applied no additional traffic should be allowed on the site. 

Lime and Other Amendments to Adjust pH

Testing throughout the state has verified that using adapted or native species eliminates the need to use lime or soil-acidifying agents.  The species and varieties called for in this manual will survive and produce effective stands of vegetation without pH-altering amendments.

Lawns, playing fields, and other high maintenance areas may require lime if extremely lush growth is required.  These areas will only benefit from such application if the original pH is lower than 5.0.

Topsoil

The topsoil layer in undisturbed areas in Alaska is often very thin and expensive, or impractical, to salvage.  However, this layer is a source of native seed, plant propagules, organic matter, and soil microbes which can enhance the quality of the substrate being revegetated.  If possible, top soil should be salvaged.

Gravelly sites tend not to be highly erodible. If some fine particles are present in the gravelly soil, adapted species will grow without additional topsoil.  In fact, the addition of a layer of topsoil on a gravel surface can increase erosion potential.