A study involving Mn rates and soil pH levels was conducted in 1985 and 1986 with flue-cured tobacco (Nicotiana tabacum L.) in Georgia since reports from North Carolina indicate that Mn may be beneficial for tobacco on some low Mn soils with pH levels of 6.2 and higher. The site was a Pelham loamy sand (thermic, Arenic Paleaquult) where yield response to Mn had been documented for corn (Zea mays L.), peanut (Arachis hypogaea L.), soybean [Glycine max (L.) Merr.], and wheat (Triticum sativum L.) in previous experiments. Factorial treatments initiated in 1977 were three soil pH levels (5.4, 6.2, and 7.2 in 1985) and Mn rates of 0, 10, 20 and 40 kg/ha applied annually as MnSO₄ except in 1981 and 1985. Leaf Mn increased with increasing rates of Mn and decreased within each Mn rate as soil pH increased. Leaf yield and quality were not affected by Mn application even though leaf Mn ranged from 13 to 129 mg/kg in 1985 and from 21 to 307 mg/kg in 1986. A mild Mn deficiency symptom, "flecking", was observed where leaf Mn of mature cured leaves was 13 mg/kg. Leaf yield increased with increasing pH levels in 1986, but this was probably the result of a high incidence of fusarium wilt (Fusarium oxysporium f. nicotiane) on plants grown in low pH plots. The incidence of fusarium wilt decreased with in­creasing pH. Data agree with long term field observations in Georgia that Mn deficiency is more probable for major agronomic crops other than tobac­co grown on high pH (>6.5) soils.

(Full article published with kind permission from "Tobacco International")