Soil and Plant Factors Influencing Accumulation of Dry Matter in Burley Tobacco Growing in Soil Made Acid by Fertilizer¹

Abstract

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.

Effects of soil ph, nitrogen source, phosphorus, and molybdenum on early growth and mineral nutrition of burley tobacco

“…Although substantially greater decreases due to NH4 have been frequently reported (30), such factors as level of fertilization, source of N, plant species utilized, and soil buffering capacity all may influence the extent to which N form affects soil pH. The pH decreases in this experiment are similar to those recorded by Sims and Atkinson (31,32) and Reneau and co-workers (29). For treatments receiving NO3-N, a measurable increase in pH occurred only at initial pH of 6 In Experiment 2, application of NH4 to the soil also resulted in soil pH decreases (Table 4) of 0.3 to 0.4 pH units (initial pH 6.8).…”

Soluble calcium fertilizer effects on early growth and nutrition of burley tobacco

“…In the current study, it is not known whether the higher nutrient concentrations due to Ca are the result of higher influx rates of nutrients into root cells or to lower efflux rates. In burley tobacco culture, soluble Ca most likely lessens or prevents K efflux, since soil pH often is lowered markedly by fertilizer induced soil acidity (3,4,5). Also, Ca may partially negate any inhibitory effects of the higher concentrations of H in the soil environment on K uptake by plant roots.…”

“…Hence, initial soil pH needs to be near 6.6 in order to maintain pH at midseason in the range of 5.6 to 6.2, principally to control Mn toxicity, Mo deficiency, and to enhance overall nutrient availability (5,6,7,8,9).…”

A solution culture study of manganese‐tolerant and ‐sensitive tobacco genotypes

“…In Kentucky and other regions of the Eastern United States, Mn toxicity in tobacco is due primarily to continuous field application of acidifying fertilizers (Sims and Atkinson, 1974;Sims et al, 1984). Although liming ameliorates Mn toxicity in most soils, the failure to lime adequately, combined with continuous tobacco production fosters soil acidification.…”