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This article in AJ

  1. Vol. 70 No. 6, p. 1041-1047
    Received: Feb 10, 1978

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Interactions of Early- and Late-planted Winter Wheat with Their Environment1

  1. D. C. Thill,
  2. R. E. Witters and
  3. R. I. Papendick2



In eastern Washington, early fall-planted wheat (Triticum aestivum L.) has a greater yield potential than late-planted wheat, and the additional fall growth of the early-planted wheat improves erosion control after fallow. The purpose of this study was to investigate plant-environmental interactions of early- and late-planted wheat in the field and to determine morphological, physiological, and environmental interactions that contribute to the greater yield potential of the early-planted winter wheat under disease-free conditions.

Plant growth and development was evaluated on ‘Nugaines’ soft, white winter wheat planted in a Palouse fine silty soil (mesic pachic ultic Haploxerolls) in early September (EPW) and early October (LPW) in eastern Washington. Recommended rates of fertilizer for maximum yields were used and the wheat was sprayed with a fungicide in early spring to control Cercosporella foot rot. Canopy apparent photosynthesis and transpiration were measured throughout each day in the field by infraed gas analysis using an open system equipment design. Beginning in early spring, leaf area, number of tillers and heads, and plant dry weight were determined at 1- to 2-week intervals. From these determinations, leaf area index and leaf area duration were calculated. In addition, leaf water potential and soil moisture depletion were measured throughout the growing season by use of a Scholander-type pressure chamber and neutron moisture meter, respectively.

The EPW produced more grain field, tillers m−2, heads m−2, and kernal weight than the LPW, but significantly fewer kernels per head. Growth analysis indicated that EPW and the LPW plants maintained nearly equivalent internal plant water potentials throughout the growing season. Aparently, the EPW had superior yield potential because its root system was capable of extracting sufficient soil water during the spring and summer to maintain a plant water status that supported CO2 fixation per unit area of leaf equivalent to that of LPW. Thus, the maintenance of greater leaf area by the EPW during the grain-filling period provided the basis for greater net assimilation and grain yield.

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