Influence of soil pH and molybdenum fertilization on the productivity of Maryland tobacco. I. Field investigations

To gain information on soil factors which may limit productivity of tobacco on Coastal Plain soils in Maryland, studies were conducted on Monmouth sandy loam soils in 1982 to 1984 and in 1988. The 1982-1984 study involved the application of dolomitic lime in 1982 at rates of 0, 3.6, 7.3, and 14.6 M ton/ha which achieved pH values of 4.4, 4.7, 5.0, and 5.3, respectively, in combination with annual applications of supplemental molybdenum (Mo) at rates equal to 0, 0.28, 0.55, and 1.1 kg/ha. The 1988 study involved lime application rates of 6.0, 17.0, and 25.0 M ton/ha to achieve pH values of 5.0, 5.6, and 6.0, respectively, in combination with Mo rates equal to 0, 0.5, and 1.0 k/gha. Studies were also conducted in 1988 involving the application of 0, 0.55, and 1.10 kg/ha supplemental Mo without lime additions to two sites having pH values of 5.0 and 5.5, respectively. Cured leaf yields, total nitrogen (N) and alkaloid levels were measured in all studies. Leaf Mo levels were monitored in the 1988 studies. Applications of 14.6 M ton/ha of lime in 1982 induced significant yield increases which averaged 13.8% over controls in the 3-year study. No significant benefits from supplemental Mo were found at the 0 and 3.6 M ton/ha lime treatments (< pH 4.7) in the 1982-84 study or in any of the 1988 studies. However, 1.1 kg/ha Mo applied in combination with 7.3 and 14.6 M ton kg/ha lime increased yields by 16 to 22% above the control treatments in the 1982-84 study, and by 17.8% and 18.7% when applied in combination with 6.0 and 25.0 M ton/ha, respectively, in 1988. In 1988, leaf Mo increased with increased Mo rates, especially at higher pH values. Treatment effects on total N and alkaloid levels were non-significant in most instances suggesting that N metabolism activities in the control plants were not being limited by plant available Mo (0.10 microgram/g) in the soil.