Nitrogen Fixation Capacity of Field-Grown Bean Compared to Other Grain Legumes1
- M. I. Piha and
- D. N. Munns2
The generally poor symbiotic performance of field-grown bean (Phaseolus vulgaris L.) has been attributed to difficulty in establishing effective symbiosis and to genetic variability in N-fixation capacity. The ontogeny of N accumulation by symbiotic and N-fertilized common bean selected for high N-fixation potential was compared to commercial bean varieties, cowpea [ Vigna unguiculata (L.) Walp.], and soybean [Glycine max, (L.) Merr.] in a N-deficient field (Reiff sandy loam, Typic Xerorthent). Cowpea and Soybean accumulated N to higher levels and at faster rates than did common bean, whether symbiotic or N-fertilized. Relative N accumulation (N accumulation in symbiotic plants relative to that in fertilized plants) during vegetative growth was highest for cowpea, intermediate for soybean and late maturing bean, and lowest for early maturing commercial bean varieties. Relative N accumulation during the late growth stages was always higher than in the early stages. Absolute rates of N accumulation declined after flowering in both symbiotic and N-fertilized plants. Early maturing bean and cowpea reached physiological maturity at the same time, but bean accumulated more of its N during early development and had a shorter vegetative growth period. Despite weak vegetative N-fixation capacity, some late maturing bean cultivars achieved similar final harvest N accumulation and seed yield whether they were N-fertilized or not.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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