EFFECT OF POTASH MANURING ON THE PRODUCTION OF ORGANIC MATTER

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Abstract
Assimilation of CO2, as measured by its removal from an air current passing through a sealed chamber in which plants are growing under fully controlled conditions, is taken as an indicator of organic matter production. Varying amts. of K2O were supplied to the plants growing under high and low levels of N and P nutrition. At low levels of nutrition the maximum CO2 assimilation was reached with a comparatively low K2O application; with a high level of nutrition, the maximum was not reached until 10 times as much K2O had been applied. Similar results were obtained at several stages of growth of wheat, the plant used in these investigations. Transpiration increased with the increments in K2O fertilization but chlorophyll content reached a maximum and then decreased. Chlorophyll content of leaves is thus no criterion of their assimilative ability. Using the "relative protein value" of Paech as the criterion of protein formation, the first 3 increments of K2O increased protein formation, after which it was constant with further potash increments. Potash fertilization apparently had no effect on diameter of stomata. Assimilation of CO2 in the plant reached its maximum point and began declining before the maximum point of protein formation occurred.

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