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This article in CS

  1. Vol. 27 No. 6, p. 1177-1184
    Received: Sept 5, 1986



Ozone and Soil Moisture Deficit Effects on Nitrogen Metabolism of Soybean1

  1. R. B. Flagler,
  2. R. P. Patterson,
  3. A. S. Heagle and
  4. W. W. Heck2



Ozone can interfere with nitrogen metabolism of soybean [Glycine max (L.) Merr.], but the effect of O3 on nitrogen metabolism of field-grown soybean has received only limited attention. A two-year field study was conducted to determine the effects of soil moisture deficit and O3 on nitrogen metabolism of ‘Davis’ soybean. Two soil moisture regimes, well-watered and water-stressed (WS), were established using different irrigation frequencies. Ozone treatments ranged from 0.025 to 0.107 μL L−1 (7-h day−1 seasonal means) and were charcoal filtered, nonfiltered, and two (1983) or four (1984) levels of 03 addition to nonfiltered ambient air entering open-top field chambers. Growing conditions were quite different between the two years. The 1983 season was dry and hot throughout vegetative growth. In contrast, 1984 was wetter and cooler, with no requirement for irrigation during vegetative growth. Effects due to WS were more pronounced than those due to O3. Nitrogen fixation, estimated by the acetylene reduction (AR) technique, was decreased by both O3 and WS treatments in both years. As O3 concentration increased, there was a decrease in total AR activity and a more rapid decline of activity during reproductive growth. Water deficit decreased AR activity significantly both years. The activity of nitrate reductase (NR) was also decreased by WS treatments. Ozone effects on NR activity varied between years. Rates of N accumulation were generally lower in higher O3 and WS treatments. The partitioning of N among various plant parts and concentrations of N within plant parts were altered in WS treatments during all stages of growth and to a far lesser extent by O3 treatments during reproductive growth. While there were no significant O3 ✕ water regime interactions, the results demonstrate that soil water status has a pronounced effect on plant response to O3.

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