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LOFTIS STELLA G.; KURTZ, EDWIN B.
Soil Science: March 1980
ORIGINAL ARTICLE: PDF Only
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ABSTRACTNitrogen fixed by atmospheric reactions and by blue-green algae provides an important source of nutrient to semiarid soils. We tried to measure the amount of N2 fixed in an area of west Texas. Field studies estimated the amount of inorganic nitrogen added to the soil by nitrates in rainfall and nitrogen fixed by blue-green algae. Colorimetric analysis of rainwater, using phenoldisulfonic acid reagent, indicated that a 1-cm rainfall brought an average of 39 g NO3-N/ha to the soil. The acetylene-reduction technique was used to measure the nitrogen-fixation capacity in the field by crusts of blue-green algae and mold. With an estimated 15% surface coverage by algal crusts, up to 1.3 g N2/ha/h may be added to the soil by blue-green algae for each of the daylight hours during the first 24 h after a rainfall. Frequent showers caused more fixed nitrogen to be added to the soil (from atmospheric reactions and blue-green algae) than the same amount of rainfall occurring at one time.

Nitrogen fixed by atmospheric reactions and by blue-green algae provides an important source of nutrient to semiarid soils. We tried to measure the amount of N2 fixed in an area of west Texas. Field studies estimated the amount of inorganic nitrogen added to the soil by nitrates in rainfall and nitrogen fixed by blue-green algae. Colorimetric analysis of rainwater, using phenoldisulfonic acid reagent, indicated that a 1-cm rainfall brought an average of 39 g NO3-N/ha to the soil. The acetylene-reduction technique was used to measure the nitrogen-fixation capacity in the field by crusts of blue-green algae and mold. With an estimated 15% surface coverage by algal crusts, up to 1.3 g N2/ha/h may be added to the soil by blue-green algae for each of the daylight hours during the first 24 h after a rainfall. Frequent showers caused more fixed nitrogen to be added to the soil (from atmospheric reactions and blue-green algae) than the same amount of rainfall occurring at one time.

© Williams & Wilkins 1980. All Rights Reserved.