Robert C. Pearce

Calcium and bicarbonate effects on the growth and nutrient uptake of burley tobacco seedlings: Hydroponic culture 1

Abstract In soilless production systems, water quality can have a major impact on the growth of plants. It has become evident that moderately alkaline water is a problem for tobacco transplant growers in some regions of Kentucky. To determine the level of bicarbonate (HCO3 −) alkalinity, which is detrimental to burley tobacco transplants, and to better understand the effect of calcium (Ca) and the interaction of HCO3 − and Ca on the growth of burley tobacco transplants grown in a float system, three levels of CaCl2 (25,75, and 125 mg L−1 Ca++) in factorial combination with five levels of HCO3 − (0, 122, 244, 366, and 488 mg HCO3 −L−1) were tested in nutrient solution culture. Four‐week‐old burley tobacco (Nicotiana tabacum L. var. KY‐907) seedlings were transplanted to 18‐L containers filled with aerated Hoaglands solution with the different levels of calcium and HCO3 − for two weeks. High HCC3 − alkalinity caused root system damage and plant growth inhibition, but did not induce iron (Fe) chlorosis. A s...

Calcium and bicarbonate effects on the growth and nutrient uptake of burley tobacco seedlings: Float system 1

Abstract High levels of bicarbonate (HCO3 −) alkalinity have been shown to affect the growth and nutrient uptake of tobacco seedlings in solution culture. The objective of this study was to determine the effect of HCO3 − on the nutrient uptake of burley tobacco seedlings grown in a float system. Float bays of a size to accommodate individual float trays were filled with 40 L of deionized water. A commercial 20–10–20 (20% N, 10% P2O5,20% K2O) water soluble fertilizer was added to give 100 mg N L−1. Sodium bicarbonate and calcium chloride were added to provide a factorial combination of 5 levels of HCO3 − (0, 122, 244, 366, and 488 mg L−1) and three levels of calcium (Ca2+) (25, 50, and 75 mg L−1). Pelleted burley tobacco seed (var. KY 907) were sown into 200‐cell float trays filled with peat‐vermiculite medium. Plants in all treatments appeared normal. HCO3 − alkalinity above 244 mg L−1 limited the growth of tobacco seedlings. Total nitrogen (N), phosphorus (P) and potassium (K) concentration in the shoot ...

Occurrence of frogeye leaf spot, caused by Cercospora nicotianae, in greenhouse tobacco transplants in Kentucky

Frogeye leaf spot (FLS), caused by Cercospora nicotianae, has traditionally been considered a minor disease occurring on older, low-growing leaves of tobacco (Nicotiana tabacum L.). Historically, FLS was even considered desirable by some burley tobacco grading experts as an indicator of crop maturity. In recent years, however, multiple cured crops grown in south-central Kentucky have been rejected by buyers due to excessive FLS. In May 2017, symptoms of FLS were identified for the first time in burley tobacco transplants grown in greenhouse floatbeds in Metcalfe, Allen, and Barren Counties, the same region of Kentucky where FLS severity has resulted in rejected crops. Lesions were characterized by a tan-white center surrounded by a narrow brown ring with a chlorotic halo. Black sporulation was macroscopically visible in lesion centers under high humidity. Incidence of FLS was 0.5% - 5% of transplants, with a maximum of 10% severity on the total leaf area of an individual transplant. Diseased transplants w...