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This article in AJ

  1. Vol. 78 No. 1, p. 120-123
     
    Received: June 28, 1984


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doi:10.2134/agronj1986.00021962007800010025x

Use of Portable Rainout Shelters to Induce Water Stress1

  1. K. L. Clawson,
  2. B. L. Blad and
  3. J. E. Specht2

Abstract

Abstract

Rainout shelters provide a method for developing drought stress under field conditions in years when rainfall is adequate. The primary objective of this study was to determine the feasibility of using portable rainout shelters in water stress studies. The study was conducted at Mead, NE in 1981 with three near-isogenic lines of soybeans [Glycine max (L.) Merr. cv. Harosoy] differing in pubescence density. The soil at this site is a Typic Argiudoll (Sharpsburg silty clay loam). Soybean isolines were planted in small plots, 46 m2 in size and were either rainfed or rainout sheltered. The shelters covered an area of 18 m2. The plots were instrumented with leaf thermocouples, strip net radiometers, and neutron access tubes. Phytomass and leaf area index (LAI) measurements were made in the 12 small plots and from four adjacent large plots maintained under rainfed conditions. Leaf temperature was 8 °C warmer and net radiation was 40% lower at midday in the sheltered plots compared to the unsheltered plots. The shelters induced water stress as indicated by a rise in leaf temperature of about 2 °C. However, significant lateral and/or upward movement of soil water into the sheltered plots greatly reduced the effectiveness of the shelters. Phytomass accumulation and LAI from the small and large plots did not agree. The errors of the estimates in the small plots were much greater than those from the large plots. Because of our results, we do not recommend the use of small, portable rainout shelters.

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