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This article in AJ

  1. Vol. 70 No. 5, p. 816-823
     
    Received: Sept 28, 1977


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doi:10.2134/agronj1978.00021962007000050028x

Analysis of Fallow-Farming Systems in Semi-Arid Africa Using a Model to Simulate the Hydrologic Budget1

  1. Anthony E. Hall and
  2. Claude Dancette2

Abstract

Abstract

A model was developed to predict bare soil evaporation, crop water use, and the distribution of water in the soil. Comparisons with hydrologic budget data obtained in the field with bare soil, cowpeas (Vigna unguiculata (I.,) Walp.), and millet (Pennisetum typhoides (Burm. f.) S. and W.) indicated that the models performed adequately for the conditions and objectives of the study. Simulations of annual fallow, predicted that the amounts of water conserved in the soil would rapidly decrease with decreases in annual rainfall. Simulations of partial year fallow, achieved by weed removal after harvest of 90-day or 75-day millets were evaluated through an 8- year period of wet, dry, wet, and dry years having an average, monomodal rainfall of 502 mm. The simulations predicted that substantial quantities of water may be conserved in the soil by partial fallow during wetter years. More soil moisture would be conserved with the shorter cycle variety, but the longer cycle variety would have greater meed for this moisture in this climatic zone during dry years, indicating a possible advantage of rotations involving short cycle, and long cycle crops. Shorter cycle varieties and partial fallow could also increase ground water recharge. The simulations predicted that present varieties may only use a small proportion of the moisture that may be stored below 150 cm depth in the soil by partial fallow, indicating a possible need for developing varieties with faster growing, deeper, root systems.

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