Rate of nitrogen release for various slowly soluble fertilizers was significantly different from that of a standard fertilizer blend (3 parts urea-form to 1 part superphosphate) on both an equal weight of fertilizer and equal weight of nitrogen basis. Growth promotional effects of these materials (urea-form, magnesium ammonium phosphate, coated diammonium phosphate, and Torula yeast) were roughly equivalent to the standard blend and to each other in seedling pot trials. Sources of vitamins and hormones were not effective in promoting seedling growth with or without fertilization. Physical form or placement of fertilizer was not critical in seedling pot studies except for the greenhouse environment where bottom placement was significantly better than side placement. Maximum growth and highest foliage content of N and P were obtained in a Ferrelo sandy loam with a P source fertilizer while the best growth of fertilized seedlings in a Hembre silt loam was obtained with a balance of N and P source fertilizers. Similar results with these soils in the field suggest that pot studies could be used to prescribe fertilizer formulations for different soils. Combinations of urea-form magnesium ammonium phosphate may be a better formulation for pellet fertilizers than the standard blend. Use of a soil barrier between seedling roots and Fertilizer is recommended.
Document Type: Journal Article
Forestry Supervisor Retried, Central Research Division, Crown Zellerbach Corporation, Camas, Wash.
Publication date: November 1, 1966
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