Fig. 26: Packets, tablets and pellets of slow-release fertilizers that can be used safely at time seedlings are planted.
Fertilization of seedlings at planting time must be done with care. Seedlings can be injured or killed if soluble fertilizers such as nitrogen and potassium come too close to roots. Banding fertilizers without adequate prior weed control also stimulates excessive competition from herbaceous vegetation, thereby reducing tree survival and growth. In addition, some species, particularly the pines, have relatively low fertility requirements and may not require fertilization on many sites. Research results in Ohio show that only small increases in shoot growth resulted during the first three years after planting as a result of fertilization of six Christmas tree species grown on sites having varying moisture and native fertility conditions.
On sites where moisture conditions are favorable but fertility is low, the more demanding species such as spruces, true firs and Douglas-fir can sometimes benefit from fertilization at planting time. On such sites, use of slow release fertilizers in either pelleted or granular forms usually gives best results. Suitable fertilizers include several formulations of different metal ammonium phosphates (8-40-01, 7-40-6, etc.). These can be placed in holes adjacent to but separated from the roots or placed in special packets or tablets that can be placed in the planting holes themselves (Fig. 26). About one ounce of fertilizer is needed for each tree.
1. The designation 10-10-10, 15-15-15, 12-6-6, etc. on a fertilizer bag refers to the guaranteed minimum percent by weight of nitrogen, phosphorus and potassium (in that order) contained in the fertilizer material. Thus, a 12-6-6 fertilizer would contain 12 percent total nitrogen, 6 percent phosphorus expressed as P2O5 and 6 percent potassium expressed as K2O.
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| Fig. 26: Packets, tablets and pellets of slow-release fertilizers that can be used safely at time seedlings are planted. |