Dry matter accumulation, N uptake, and chemical composition of tobacco grown with different N sources at two levels of K

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Abstract
Tobacco (Nicotiana tabacum L. cv. KY 14) was grown for 5 and 9 days in nutrient solutions containing 3.0 mM N and either 0.1 or 1.0 mM K+. N was supplied either as NO‐ 3 or a mixture of NO‐ 3 and NH+ 4 at 3:1 and 1:1 ratios. Solutions were changed daily to minimize pH changes and nutrient depletion. After 9 days tissue dry weights of plants supplied 0.1 mM K were generally less than plants grown with 1.0 mM K+; ; the presence of NH+ 4 at the low K level did not decrease dry matter accumulation further. Maximum dry matter accumulation occurred at the high K level with 2.25 mM NO‐ 3 and 0.75 mM NH+ 4. Cumulative NO‐ 3 uptake at high K was greater than for low K for the respective N treatments. Cumulative NH+ 4 uptake was not affected by K level or NO‐ 3 to NH+ 4. ratio. Tissue totals cation to anion ratios were not greatly affected and tissue N concentrations in plants receiving both NO‐ 3 and NH+ 3 were generally greater than NO‐ 3 only. These results indicate that short term growth of tobacco seedlings was greatest when equivalent N was supplied as 2.25 mM NO‐ 3 and 0.75 mM MH+ 4.