Leaf-burn of tobacco as influenced by content of potassium, nitrogen, and chlorine

A study was made of the influence of the contents of potash, reduced nitrogen (organic and ammonium forms), and chlorine upon the leaf-burn of untreated and chemically treated cured tobacco. The specific influence of each of these constituents in the leaf upon this quality was evaluated by analyzing the data statistically. The influence of the amount of exchangeable potash in the soil upon the potash content of the leaf and upon the leaf-burn was also studied. The results may be summarized as follows: 1. When the relative influence of the contents of potash, reduced nitrogen, and chlorine of the leaf on the leaf-burn of untreated tobacco was determined by a statistical analysis of the data from burn tests and chemical analyses, the following equation was obtained: Log burn in seconds = -.009 + .583A + .473A(2), where A = .913 + .295 X % K2O -.431 X % N -.354 X % Cl. From a comparison of their coefficients, it was found that on the percentage content, reduced nitrogen is 1.46 times more detrimental to leaf-burn than potash is beneficial, and 1.22 times more detrimental than chlorine. When the influence of all three constituents was considered, as indicated by this equation, the coefficient of correlation was found to be .921. This relatively high value indicates that all of the main factors involved in the leaf-burn of the tested samples had been considered and emphasizes the importance of considering the influence of all three constituents instead of that of only one or two. 2. A similar analysis of the data obtained from leaves impregnated with known quantities of the three constituents gave the equation: Log burn in seconds = .443 -.057B + .554B(2), where B = 1.826 + .315 X % K2O -.417 X % N -.534 X % Cl. The essential features of this equation verify most of the conclusions derived from the equation for the untreated leaves. The chlorine content of the treated leaves was somewhat more detrimental to leaf-burn than that of the untreated ones. This was believed to be due to this element being combined almost entirely with potassium in the treated leaves but only partially so in the untreated ones. 3. The amount of exchangeable potash in the soil on which the tobacco was grown was found to have a direct logarithmic relation to the potash content of the leaf. According to this relation, a disproportionate increase in the amount of exchangeable soil potash was required to produce each successive increase in the potash content of the leaf. A statistical analysis of the data gave the equation: % K2O in leaf = 4.49 log lbs. exchangeable K2O/A-8.62. By substituting the right side of this equation for its equal, the potash content of the leaf, in the equation for the untreated leaves, a new equation is derived from which the amounts of exchangeable potash in the soil required to give desired leaf-burn values may be computed.