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This article in AJ

  1. Vol. 93 No. 4, p. 902-910
     
    Received: Sept 6, 2000
    Published: July, 2001


    * Corresponding author(s): whfick@ksu.edu
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doi:10.2134/agronj2001.934902x

Soil Nitrogen Mineralization in Mixtures of Eastern Gamagrass with Alfalfa and Red Clover

  1. Jose L. Gila and
  2. Walter H. Fick *b
  1. a Instituto Nacional de Investigaciones Agrícolas (INIA), CENIAP, Instituto de Investigaciones Zootécnicas, Apartado 4653, Maracay 2101, Aragua, Venezuela
    b Dep. of Agron., Throckmorton Hall, Kansas State Univ., Manhattan, KS 66506-5501

Abstract

The amount and rate of soil N mineralization often influences the productivity and persistence of a grass–legume mixture. This research investigated soil N availability in monoculture and binary mixtures of alfalfa (Medicago sativa L.) or red clover (Trifolium pratense L.) with eastern gamagrass [Tripsacum dactyloides (L.) L.] on sandy and clay loam soils near Manhattan, KS. Soil inorganic N and in situ net N mineralization were monitored monthly during the growing seasons of 1996 and 1997. Soil inorganic N was two- to threefold higher with alfalfa, red clover, and gamagrass–alfalfa mixture than with gamagrass in monoculture at the end of 1996. At the midseason of 1997, soil inorganic N was three- to ninefold higher at the clay loam site, but at the sandy site, only alfalfa monoculture was three- to fivefold higher than the other treatments in both years. Soils under alfalfa at both sites in 1997 had the highest cumulative net N mineralized (35–100 kg N ha−1 yr−1), followed by the gamagrass–legume mixtures (15–62 kg N ha−1 yr−1) and then the gamagrass monoculture treatment (2–15 kg N ha−1 yr−1). A high correlation (r 2 > 0.9, P < 0.05) was found between C/N ratio of the aboveground biomass and the total net N mineralized in the 2nd yr for both sites, suggesting that litter quality is an important driving variable on N mineralization. Our results emphasize the importance of forage legumes in maintaining soil quality and productivity and quality of forage mixtures.

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Copyright © 2001. American Society of AgronomyPublished in Agron. J.93:902–910.