Nicotiana tabarum L. cv. ‘Burley 21’ was grown in the field to determine the influence of rate of N fertilization on accumulation of dry matter and certain nitrogenous constituents during the growing season. Nitrogenous compounds in tobacco are presently of interest from a human health standpoint and the chemical constituents of tobacco leaves are known to be associated with dry matter accumulation. Accumulation of dry matter, protein N, and total N in plants treated with high rates of N fertilizer (up to 450 kg N/ha) was slower than in plants not fertilized or those fertilized with low rates of N during the early part of the growing season. The reduced rates of accumulation were particularly evident until near the flowering stage of growth (70 to 77 days). Thereafter, accumulation plants treated with high rates of N equalled or exceeded that in plants treated with low rates. Weight of dry matter and all measured constituents were greatest in high N treatments at harvest; however, N fertilizer delayed maturity 1 to 2 weeks. Exchangeable Mn in soil and concentration of Mn in leaves near 40 days increased as N fertilizer level increased. Values for Mn were lower than the literature would suggest as likely to produce toxicity in plants. Thus, factors in addition to Mn toxicity must be considered to explain the observed reduction of early growth by N fertilizers.

A field experiment was conducted to elucidate factors influencing dry matter accumulation in tobacco (Nicotiana tabacum L. cv. ‘Burley 21’) growing in soil whose acidity was increased by fertilizer. Relatively large amounts of commercial fertilizers commonly are added to soil in burley tobacco production and knowledge of the effects of such additions on dry matter accumulation may lead to increased yields of cured leaf and improved usability of cigarette smoke. Samples of soil and plant material were obtained at varying dates during the growing season and were chemically analyzed. Varying soil pH levels were obtained from applications of N as ammonium nitrate at rates of 0, 90, 180, and 360 kg N/ha. The addition of N fertilizer to Maury silt loam soil with an initial pH of 6.2 significantly increased exchangeable Mn and decreased soil pH, exchangeable Ca, and concentrations of available MoO4−2 and H2PO4−. Exchangeable Mg and K were little affected by N fertilizer at any sampling date. Much of the decrease in exchangeable Ca may be attributed to leaching with NO3− by excessive rainfall early in the season. Evidence indicated some delay of nitrification of NH4+ in plots fertilized at the 360 kg N rate. Nitrogen fertilization of tobacco increased concentrations of Mn in leaves, but levels were not judged to be excessive for normal growth. A tendency existed for concentrations of Ca and Mg to be decreased by N at 40 days after transplanting and concentrations were near deficiency levels for Ca at this date, although exchangeable soil Ca levels exceeded 1500 ppm. In contrast, at 77 days and at harvest, N fertilizer significantly increased plant concentrations of Ca and Mg. Molybdenum concentrations in leaves from high N plots were only 20 to 50% of those in plots unfertilized with N. Concentrations of MoO4−2 in leaves from fertilized plots were near deficiency levels for most of the growing season. The data suggested interaction of MoO4−2 and Mn, and of Mn with Ca and Mg within the plant. Correlation and regression analyses revealed significant relationships of soil measurements near transplanting and dry matter at 40 days and of plant constituents and dry matter at all dates. Results indicated the depression of dry weight by N fertilizer noted previously during early growth was the direct or indirect result of fertilizer‐induced soil acidity.

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The residue of maleic hydrazide, a systemic sucker control agent, was quantified on air-cured hurley tobacco (Nicotiana tabacum L.) that had been subjected to different application rates, harvest dates, and combination treatments with a fatty alcohol sucker control agent. Residue levels were decreased by allowing longer periods of time between application and harvest, lower application rates, and the use of single rather than split applications. Residue levels were higher from the upper portions of the plant and from laminae compared to midvein tissue. Levels ranged from 21.0 to 152.3 /ig/g dry weight. Chemical treatment of burley tobacco with sucker retardants significantly increased yields over the nontreated hand-suckered plots especially at late harvest dates.

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