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The purpose of the present paper is to determine the effect of the Ca‐Mg ratio in solution and in the soil on the solubility and availability of certain plant nutrients. In recent years many papers have been published on the effect of the Ca‐Mg ratio on crop production. Certain papers and unpublished data have indicated that the Ca‐Mg ratio affects the solubility of other plant nutrients, esepecially phosphorus, including some of the minor or trace elements. Nutrient solutions have been made up and mixed with common soil clay kaolin as an adsorbing component. The solubility of B, Mn, Zn, Cu, K, and P were determined. Soil from the Kingman area which is quite low in Mg was obtained for greenhouse studies. Wheat and sorghum were grown and analyzed for the above elements. Plant uptake of the nutrients was plotted against the Ca‐Mg ratio. The results showed: A varying Ca:Mg ratio in Kingman soil produced a difference in the weight and height of the plants grown with a maximum plant growth at a Ca‐Mg mol. ratio of 4‐1. All the nutrient elements studied were affected by a varying Ca:Mg ratio in the soil. The effects observed on the minor elements in wheat and sorghum agree qualitatively with most of the effects observed in nutrient solution studies. No direct correlation was found between the ratio of Ca:Mg in the soil as compared to the ratio in the plants, but a general correlation occurs. An overall maximum uptake of the minor elements seems to be provided for both wheat and sorghum at a Ca:Mg ratio of approximately 4:1. A high magnesium soil favors the uptake of Mn and Zn by sorghum and K, B, and Mn by wheat.

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The de-arc plasmajet has been applied to a large number of emission problems since its introduction in 1959 because it offers reduced matrix effects, stability, and moderate sensitivity. However, its use has been significantly limited due to operating costs associated with its high inert gas flow rates. A new excitation source, based on the principle of the plasma jet, has been developed that can operate at a much lower cost. The source operates from a conventional dc-arc power supply and uses commercially available electrodes. Total inert gas consumption is less than 2.5 liters/min. Stability of the source is better than 1% and reproducibility is approximately 4%. An excitation temperature of 5800 K was calculated from the relative intensities of several vanadium lines. The source can be operated continuously for several hours at a time. Design and some characteristics of the arc are presented. Detection limits are given for 12 elements. Six of the elements (Ca, Cr, Fe, Li, Ni, and Y) have detection limits below 10 ng/ml. Analytical response for the elements studied is linear over a wide concentration range. A calibration curve for Ca is presented which is linear over more than four orders of magnitude.