Nitrogen and water stress interact to influence carbon-13 discrimination in wheat
2001
Clay, D.E. | Engel, R.E. | Long, D.S. | Liu, Z.
The impact of interactions between water and N stress on 13C isotopic discrimination (delta) is not well understood. The objective of this study was to determine the impact of N on delta in wheat (Triticum aestivum L.) grown under low, moderate, and high water stress. In a field study located near Havre, Montana, USA (48 degrees 30' N lat. and 109 degrees 22' W long.), wheat grown under three different water stress environments (low, moderate, and high) was fertilized with three different N rates (none, moderate, and high). Each treatment was replicated four times. The grain N fertilizer use efficiency increased as water stress decreased. A differential response of delta to N was observed. In general, if plants were grown under high water stress and N increased yield, then adding N to N-deficient plants reduced delta (-0.01 per thousand for every kg of N added); and if plants were grown under low water stress and N increased yield, then adding N had little or no impact on delta. The break point between N impacting or not impacting delta was approximately 17.45 per thousand. Under non-N limiting (moderate and high N) conditions the equation relating delta to yield was, yield (kg ha(-1)) = -11000 + 884 delta, r = 0.92**. Wheat grown under N-deficient conditions (0N treatment) did not fit this curve. By accounting for the impact of water and N stress on delta, this variation could be explained. Results from this study suggest that delta can be used to characterize N and water stress at different landscape positions in watershed studies.
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