A study was conducted to compare the effects of three fertilizer rates [High N Southern Formula, 23N–1.7P–6.6K (23–4–8) at 1.3, 1.7, and 2.0 kg N/m3 (2.2, 2.8, and 3.4 lb N/yd3)] and two production systems [pot-in-pot (PIP) or conventional above-ground (CAG)] on the growth of Heritage river birch (Betula nigra L. ‘Cully’) in 26 liter (#7) containers. Plants grown PIP had greater shoot dry weight (20%), root dry weight (31%), total biomass (27%) and root:shoot ratios (12%). Increasing fertilizer rates increased shoot dry weights but decreased root:shoot ratios. Rate of fertilizer application influenced foliar Mg, Zn, and Fe while production system had no effect. The foliar P:Zn ratio increased linearly as rate of fertilizer increased. Soluble salts and NO3-N in the leachate increased linearly as rate of fertilizer increased at 15 and 60 days after application (DAA), whereas the response was curvilinear at 120 DAA. When different, nutrient concentrations in the leachate were greater for plants grown CAG. Fertilizer longevity based on prill analysis was greater when the PIP system was used, presumably due to lower substrate temperatures during the experimental period.

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Author notes

Technical assistance of Bruce Tucker, statistical assistance of Ben Mullinix, and support of The Scotts Company is greatly appreciated.

2Associate Professor.