Critical phosphorus levels for lima bean growth

Abstract

Lima beans were grown for 6 weeks to full bloom in culture solutions with 10 P treatments ranging from O to adequate amounts of P for full growth. At harvest the plants ranged in size from small plants with small green leaves for extreme P deficiency to large plants with large leaves and no deficiency symptoms. The harvested plants were separated into 13 parts for chemical analysis. Dry weights of tops were plotted against acid soluble and total P values to give plant nutrient calibration curves. On the basis of the plant nutrient curves, ease of sampling, wide range of P conc., sharp transition zone, and other physiological considerations, the petiole from the second leaf, i. e. recently matured leaf, was selected as the plant part to sample and the acetic acid soluble phosphate as the form of P to determine. A critical value of 500 ppm of acetic acid soluble P (dry basis) was tentatively set for the 2d leaf petiole as being indicative of a P deficiency in lima bean plants. The corresponding value for total P was set at 570 ppm.