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The 2011 ASHS Annual Conference

7728:
The Impact of N Forms and Ratios, and Substrate pH on Blueberry (Vaccinium corymbosum) Root and Shoot Development

Sunday, September 25, 2011: 4:15 PM
Queens 6
Steven Kennedy, Dept. Agriculture, School of Agriculture and Consumer Sciences, Tennessee State University, Nashville, TN
Stephen Lewis, Dept. Agriculture, School of Agriculture and Consumer Sciences, Tennessee State University, Nashville, TN
Dharma Pitchay, Dept. Agriculture, School of Agriculture and Consumer Sciences, Tennessee State University, Nashville, TN
Rhizosphere environment is critical in the production of healthy and vigorous plants. Blueberry (Vaccinium  corymbosum)  is known to thrive in low pH environments. Nitrogen forms {nitrate (NO3) and ammonium (NH4)} and ratios (NH4:NO3) affect rhizosphere pH, which ultimately dictate the bio-availability of macro and micronutrients. Two experiments were conducted to investigate the range of nutrient solution pH, and nitrogen (N) forms and ratios on the root and shoot performance in blueberry. One year old seedlings were grown at six pH levels (4.5, 5.0, 5.5, 6.0, 6.5, and 6.8) in calcined clay and wood charcoal soilless substrates, and fertigated with 3.57 mM concentration of (NH4:NO3)-N at two and one hour intervals in the morning and afternoon, respectively.  Nutrient solution at pH 6.0 and below produced higher shoot and root fresh and dry mass. In the second experiment, the plants were supplied with 5.0 mM concentration of five different ratios of NH4:NO3-Nitrogen nutrient solution: a) 100:0, b) 50:50, c) 25:75 and d) 0:100 at pH of 5.5 and 6.0. Plants fed with mixed NH4 and NO3 – N at pH of 5.5 produced higher shoot and root fresh and dry mass. Nutrient solution supplied at pH of 6.0 consistently produced lower shoot plant biomass irrespective of NH4:NO3-N forms and ratios.  The NH4:NO3 (75:25) - N form nutrient solution supplied at pH of 5.5 treatment produced the highest fresh and dry mass. The 100% NO3-N nutrient solution treatment supplied at pH of 5.5 and 6.0 produced the lowest shoot and root mass, and the foliage of these plants appeared reddish.