RESPONSE OF A HYBRID POPLAR CLONE TO SOIL ACIDIFICATION AND LIMING

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Abstract
Unrooted hybrid poplar cuttings were grown in a greenhouse at varying soil pH. The soil was a loamy fine sand (pH 5.7) collected from an Ap horizon of a forest tree nursery. The pH was adjusted over a wide range by incorporating different rates of powdered lime or elemental sulfur. Lime additions failed to improve growth significantly over a 20-wk period, and excessive liming to pH 7.6 reduced shoot dry weight by 33%, probably because of decreased availability of micronutrients. Sulfur, acidifying the soil to pH 4.1, depressed growth as much as 76%. This growth inhibition was closely associated with increased Al in both foliage and soil as well as reduced foliar uptake of the other essential nutrients. Maximum height growth of clone DTAC-32 occurred between pH 6.0 and 7.0, which falls within the general guidelines for producing hardwood nursery stock. Key words: Populus, soil pH, aluminum toxicity, micronutrient deficiency