AbstractAn ecologic study was conducted to evaluate the dry matter yield response and the mean daily growth and water consumption rates of grain sorghum at four climatic sites in the tropics and subtropics. BR-54 seeds of this crop were grown in pots watered by capillarity with a specially-devised fiberglass wick-tin can reservoir technique which permitted water use measurements and drainage through the same wick. Seven weekly harvests were made of shoots and roots separately over a 52-day growth period centered on the March 22 vernal equinox . Climatic sites had a marked effect on dry matter yields (weight of the shoot). The yield response is directly related to the amount of water consumed which, at the same time, is closely related to the leaf area. However, an analysis of variance indicates that the relative growth rate, unit leaf area, water use rate, and other related indices did not significantly differ with climatic sites. As a result, it was found that there existed highly significant quadratic relationships of the relative growth rates and water use rates as a function of days after emergence when the four climatic sites were included together in regression analysis. Linear regression analysis showed also a significant relationship of unit leaf rate and water use rate on the mean daily values of solar radiation intensity and, to a lesser extent, to the open-pan evaporation.
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