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Winter Wheat Varietal Yield Differences D.C. Nielsen PROBLEM: Drought stress regularly limits winter wheat yield in the central Great Plains. I hypothesize that varieties that are better able to maintain their non-water-stressed canopy temperatures under water stress will yield higher under water stress than varieties which do not maintain their non-water-stressed canopy temperature under water stress. Monitoring of stressed and non-stressed canopy temperatures will therefore be a quick screening tool to identify varieties adapted to drought stress. APPROACH: Twelve varieties of winter wheat (TAM107, Jagger, Arlin, Prowers, Siouxland, Akron, Alliance, Norstar, 2137, Heyne, Halt, Yumar) were grown in small plots (15' by 40') under two water treatments (rainfed and full irrigation), replicated three times. Canopy temperatures were monitored daily with an infrared thermometer between 1300 and 1400 MDT. Cumulative difference between canopy temperatures of rainfed and fully irrigated plots was compared to dryland grain yield and biomass for each of the twelve varieties. Soil water was measured in five varieties on 13 Mar, 20 May, 6 Jun, and 2 Jul 2002 to assess differences in soil water extraction. RESULTS: March through June rainfall (2.83 in.) was 36% of average, fairly evenly distributed (0.96" during vegetative, 1.05" during head extension to milk, 0.83" during grain-filling). Consequently we were afforded the opportunity of evaluating differences in yield due to soil water extraction for the five varieties where soil water was measured.
INTERPRETATION: Clearly Norstar is not a variety adapted to the high temperature, high vapor pressure deficit conditions of the central Great Plains. For the other four varieties for which soil water was measured, there appears to be a relationship between yield and soil water extracted during the growing season. TAM107 was able to extract about 0.6" more soil water during the heading to milk stage period than the other three varieties (data not shown), and extracted 1.3" more water than Heyne over the entire spring and summer growth period. Most of this higher water extraction was noted from the 6th foot of the soil profile, indicating that part of TAM107's greater drought tolerance is derived from greater rooting depth/volume. FUTURE PLANS: The experimental results will be written for publication in 2003. The author may be reached via e-mail at:
D.C. Nielsen |
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