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Agronomy Journal Abstract -

Water Use, Yield, and Dry Matter Accumulation by Determinate Soybean Grown in a Humid Region1


This article in AJ

  1. Vol. 79 No. 5, p. 870-875
    Received: June 16, 1986

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  1. H. D. Scott,
  2. J. A. Ferguson and
  3. L. S. Wood2



Planning of irrigation strategies for soybean [Glycine max (L.) Merr.] requires a knowledge of the year-to-year variability associated with water use, dry matter accumulation, and seed yield. This study was undertaken to determine the relationships and variability among these plant responses at the end of vegetative and reproductive growth for irrigated (I) and nonirrigated (N) soybean grown in the field during five seasons under humid climatic conditions. Water balance components were determined by computer simulation based on actual soil, plant, and meteorological data. The soil was a Crowley silt loam (fine, montmorillonitic, thermic Typic Albaqualf). For the N soybean, seed yields ranged from 1.07 to 2.74 Mg ha−1, and dry matter ranged from 4.76 to 9.12 Mg ha−1 as the seasonal rainfall ranged from 290 to 570 mm. Variability of dry matter production was greater at the end of vegetative growth than at the end of reproductive growth. Five-year mean cumulative values of evapotranspiration (ET) during vegetative growth were 237 and 215 mm for I and N treatments, respectively. At the end of the season the 5-yr mean ET, transpiration (T), and evaporation (E) from the I soybean were 497,327, and 170 mm, respectively. These corresponding values were greater than those of N soybean of 382, 231, and 151 mm, respectively. However, when the data from the wet season were removed, the variability of ET, T, and E from the I soybean were lower than from N soybean. Under I conditions, the lowest seasonal ET (370 mm) was found in the wetter-than-normal season and the highest ET (539 mm) was found in the drier seasons. Under N conditions, ET during the wet season (370 mm) was similar to the 5-yr mean (382 mm). The year-to-year variability in this humid environment depended on soil-water management as well as the climatic conditions.

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