A preliminary study of the influence of chlorides on the growth of certain agricultural plants

A survey of previous field and greenhouse investigations of the effects of chlorides upon the growth and composition of plants discloses extremely variable results. It is apparent that the species of plant, the type of soil, and especially the complex of factors considered as climate, greatly influence these effects. In the present investigation the introduction of potassium and sodium chlorides into water cultures but slightly affected wheat plants during the first five weeks after germination. Buckwheat grown to apparent maturity in similar cultures was decidedly affected by the application of these chlorides. Although seed production remained apparently undisturbed, the length of roots and the yield of dry matter was depressed.The least production of dry matter in leaf blades and the greatest depression of water absorption per unit of dry matter of the foliar tissue occurred in the presence of sodium chloride. The radish responded only slightly, in yield and composition, to the application of potassium and sodium chlorides along with complete fertilizer in soil cultures in the greenhouse. Under similar conditions, increased production of dry matter and of the percentages of sugars therein resulted with the carrot, while the reverse was true of the parsnip. In the latter case sodium chloride was particularly injurious. The sugar beet gave the same general responses to chlorides as did the carrot, when grown in the greenhouse. While the roots were more watery where chlorides were applied, the yield of dry matter was greatly increased. The dry matter of such roots contained more glucose, but less sucrose, than that obtained from cultures in soil not receiving chlorides. Similar responses followed the application of common salt alone to beets grown in the field. The potato produced increased yields of dry matter in the tuber when potassium chloride was supplied in place of potassium sulfate, in a complete fertilizer ration, to soil cultures in the greenhouse. Relative to the percentage of starch, the Rural New Yorker and Triumph varieties of potato responded differently, the former being depressed while the latter was unaffected. The results indicated that the variety of plant was more important than the type of soil in determining this effect of chlorides. In field cultures in a dry season the application of potassium chloride in a complete fertilizer decreased the yield of dry matter in the tubers, but not the percentage of marketable tubers, of the Triumph variety. In a season which was very humid toward its close, no significant differences in composition or cooking quality were found between tubers of the Rural New Yorker variety produced where potassium sulfate and potassium chloride were employed separately in a complete fertilizer ration. Sodium chloride applied alone altered the composition of the tubers only slightly in this test, but affected their quality seriously. Determinations of the water-soluble chlorides in several types 0f Wisconsin soils have shown them to be eqivalent to about 150 to 380 pounds of chlorine per acre-foot. It is shown that this supply is inadequate for long maintaining the usual plant content of the element in crop rotations. The annual supply of chlorine in rain and snow at Madison is about 16 pounds per acre, but, judging from conditions at the Rothamsted Experiment Station, this acquisition is probably counterbalanced by losses in drainage waters. Evidence is cited which indicates that sodium chloride serves directly as a fertilizer, and that chlorine is the active element therein. Further evidence indicates a possible role of chlorides in stimulating the biological production of available nitrogen compounds in the soil, but this effect seems inadequate for explaining all of the varied responses of higher plants to the application of chlorides. Proceeding from the observed effects of chlorides upon diastase and other enzymes which act upon carbohydrates, a tentative hypothesis is adva