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This article in AJ

  1. Vol. 74 No. 3, p. 454-456
     
    Received: Feb 9, 1981


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doi:10.2134/agronj1982.00021962007400030014x

Nitrogen Production by Selected Astragalus Species1

  1. A. M. Davis2

Abstract

Abstract

Astragalus species are widely distributed throughout the temperate regions, and are particularly widespread in the northern hemisphere. The genus has a poor image because of a few toxic species (loco weeds) and its contribution to nitrogen fixation and forage production has not been studied.

A greenhouse experiment was conducted to determine the N-producing capacity of six morphologically diverse Astragalus species: A. asper Jacq., A. cicer L., A. falcatus Lam., A. glycyphyllos L., A. onobrychis L., and A. ponticus Pall., and their effect on the N content of an associated grass, ‘Nordan’ crested wheatgrass [Agropyron desertorum (Fisch. ex Link) Schult.]. The highest concentration of N was found in A. ponticus, a robust, nonforage species. Astragalus cicer was second highest. The lowest quantity was found in A. glycyphyllos. Crested wheatgrass had the highest N content when grown in association with A. onobrychis and the lowest when grown with A. falcatus. Residual soil N was highest with A. cicer.

A field study of soil N from 2-year-old plants of A. alpinus L., A. cicer, A. galegiformis L., A. glycyphyllos, A. odoratus Lam., and A. scorpurius Bge. resulted in a decreasing N gradient laterally from the center of the plant and with increasing depth. The highest soil N was at the 0 to 15 cm depth and 15 cm from the center of the crown. Each species tested had a different associated soil N level. Astragalus scorpurius had the highest soil N level; A. alpinus had the lowest.

Sufficient variation existed in the N levels associated with native and introduced Astragalus species to warrant further investigation of their N-fixing characteristics as well as their forage potential.

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