Foliar nutrient responses of oak saplings to nitrogen treatments on alkaline soils within the Missouri River floodplain


J. W. Van Sambeek, John M. Kabrick, and Daniel C. Dey

USDA Forest Service, Northern Research Station

Abstract – Amelioration of soil properties and planting of quality planting stock will be needed for successful bottomland restoration of hard-mast species on moderately alkaline soils within the lower Missouri River and upper Mississippi River. In fall 1999, four 16.2 ha fields at two conservation areas in central Missouri were cultivated with one field at both areas seeded to redtop grass and the other revegetated from the existing seedbank. A 1.3 m2 weed barrier mat was installed in 2000 around newly planted bare-root and RPM seedlings of both swamp white oak and pin oak seedlings. Due to low foliar nitrogen and chlorosis, one of the following five nitrogen treatments was applied to each oak sapling in spring 2004: application of 83 g 20N-10P-10K as slow-release ammonium nitrate, 87 g 19N-6P-9K as slow-release urea, interplanting two nitrogen-fixing false wild indigo seedlings, interplanting two buttonbush seedlings, or left untreated. Fertilizer treatments were applied annually from spring 2004 through 2006 to the weed barrier mat. Foliage nitrogen content in late July 2006 averaged 1.88 and 1.77 percent for pin and swamp white oak, respectively, with minor differences between conservation areas, ground covers, or among the five fertilizer treatments. Foliar concentrations for P, K, Ca, Mg, Zn, B, and Cu are within sufficiency ranges for white and red oaks; however, foliar N is deficient for swamp white oak while foliar S, Mn, and Fe are deficient for both species. The high soil pH at both areas may be limiting micronutrient availability, especially Mn, and negating any response to applied N.