The Influence of Applied Boron, Magnesium, and Potassium on the Growth and Chemical Composition of Red Clover Grown under Greenhouse Conditions

The objective of this investigation was to determine by means of greenhouse experiment the influence of application of boron, magnesium, and potassium on the yield and chemical composition of red clover grown on Kansas soils. A factoral design of greenhouse experiment in which a single rate of application of boron, magnesium, and potassium was made to each of four soil materials was used for the growth of red clover. Yield data were collected for four clippings of plant material. Chemical analyses were made for phosphorus, potassium, magnesium, and boron. Applications of potassium to the soil always increased the potassium content of the red clover plants and significantly the total yield of red clover for each soil type. Approximately 1% potassium in the plant material was the critical lower limit for this element, insofar as growth response was concerned. Boron applications increased the boron content of the plant material regularly and considerably. A critical lower limit of about 28 to 30 ppm B in red clover plant material was established as being necessary for prevention of boron deficiency. Cherokee subsoil was more deficient in boron than any of the surface soil samples used in this study. Magnesium applications to the soil were generally effective in increasing magnesium concentrations in the plant material only when potassium was not included as a part of the chemical treatment. A critical lower limit of about 0.5% magnesium in red clover plant material was required for optimum growth. A definite positive correlation was established between percent phosphorus and percent magnesium in the plant material. The mean value was 0.535. This correlation was most marked on soils which had low magnesium activity as indicated by relatively low percentage magnesium saturation on the exchange complex. A definite negative correlation between percentage composition of potassium and percentage composition magnesium was established. The mean value was 0.683. Potassium was shown to exert control over magnesium and not vice versa.