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Abstract
Cranberry plants, Vaccinium macrocarpon Ait. ‘Stevens’ were grown in nutrient solutions with several levels of NH4-N and NO3-N alone and in combination. The nutrient solutions were sampled weekly and analyzed for concn of NO3-N and NH4-N. It was found that the plants absorbed NH4-N preferentially to NO3-N. Dry wt and number of new shoots produced were strongly favored by the NH4 form of N. Tissue N concn was low and the plants were N-deficient when the NH4-N was depleted from the nutrient solutions before termination of the experiment, and concn was high with a sustained NH4-N supply. Plants grown in NO3-N solutions were N-deficient and had tissue N concn interm ediate to those for the extreme levels of NH4-N. No NO3-N was detected in the plant tissues. Nitrate reductase activity was absent from the aboveground portions of the plants when the possible effect of microorganisms were removed. It is concluded that NH4-N is essential for cranberry growth.