Influence of potash sources and chlorine content of fertilizers on yield of cotton

Potassium chloride as a source of potash in mixed fertilizers for cotton in the Coastal Plain and Piedmont Region of the south-eastern states is as good a form of potash as potassium sulfate, as shown by data secured in experiments on many soil types reported in this paper. Kainit has not shown up altogether as favorably as the muriate and sulfate of potash. In so far as the effect of chlorine supplied in potassium chloride is concerned, there appears no liklihood that this will become an unfavorable factor. Nine hundred pounds per acre of a 4% potash mixture, which is more than is used by cotton growers generally, if made from potassium chloride, supplies 29 pounds per acre of chlorine. From these experiments, larger quantities of this element can be supplied in the fertilizer without unfavorable effects to cotton. As much as 112 pounds per acre were supplied without unfavorable results and larger applications on some soil caused no retardation of growth or reduction in yield. Nine hundred pounds of an 8% potash mixture, made from potassium chloride, would supply only 58 pounds per acre of chlorine, while the same amount of a 12% potash mixture supplies 87 pounds of chlorine per acre. The latter is considerably below the zone of probable injury from chlorine, unless some very unusual soil conditions exist. Nine hundred pounds per acre of a 4% potash fertilizer made from kainit supplies 118 pounds of chlorine which seems near the limit of chlorine endurance for cotton, in most soils, as indicated by these experiments. The cotton plant is apparently not as sensitive to chlorine effects as the tobacco plant. Gamer, et al. (2) have recently shown that adverse nutritional effects and retarded growth of tobacco may result from considerably less than 100 pounds of chlorine per acre applied in the fertilizers, and in some cases considerable injury has resulted from 40 to 60 pounds per acre. The intensity of the effects vary with soil and climatic conditions. In the compounding of fertilizers, especially when pure chemical salts are used, it is desirable to include a variety of plant food elements, and to avoid an excess of any one element. From this point of view, it would not seem good practice to have the entire source of potash and nitrogen in a fertilizer mixture derived from muriate of potash and ammonium chloride. There are indications that the amount of chlorine supplied by the two salts when used in a mixed fertilizer applied at the rate of 900 pounds per acre is excessive for best growth and yield of cotton.