Effect of potassium on nitrogen fixation, nitrogen transport, and nitrogen harvest index of bean

Abstract

Four cultivars of Phaseolus vulgaris L., Carioca, Venezuela‐ 350, Rio Tibagi and Negro Argel, were grown to maturity in a glass house with a low (1 mol m^‐3) and a high (4.5 mol m^‐3) potassium supply. Potassium stimulated nitrogenase activity (acetylene reduction) and the accumulation of ureides in pod walls of Carioca and Negro Argel, cultivars which had the highest rates of acetylene reduction. In three of the four cultivars the higher level of potassium nutrition resulted in a greater partitioning of above ground N to the seeds. The proportion of xylem sap N in the form of the ureides, allantoln and allantoic acid (allantoate), was only slightly increased by the higher rate of potassium supply. Seed yields were increased by high potassium in the cultivars Venezuela‐350 and Negro Argel. The results suggest that potassium stimulates the transport of nitrogenous compounds to developing fruits.

Key words:

• Phaseolus
• beans
• nitrogen fixation
• harvest index
• potassium
• ureides

Notes

The Macaulay Land Use Research Institute, Bush Estate, Penicuik, Midlothian EH26 OPY, Scotland.