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Agronomy Journal Abstract -

Soil Organic Matter and Wheat Productivity in the Semiarid Argentine Pampas


This article in AJ

  1. Vol. 91 No. 2, p. 276-279
    Received: Apr 8, 1998

    * Corresponding author(s): mdzori2@pop.uky.edu
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  1. Martín Díaz-Zorita ,
  2. Daniel E. Buschiazzo and
  3. Norman Peinemann
  1. U niv. of Kentucky, Dep. of Agronomy, N-122 Agric. Sci. Ctr. North, Lexington, KY 40546-0091
    I NTA, EEA Anguil, and Fac. de Agronomía, Univ. Nacional de La Pampa, 6300 Santa Rosa, LP, Argentina
    D ep. de Agronomía, Univ. Nacional del Sur, 8000 Bahía Blanca, BA, Argentina



Crop productivity under dryland conditions is largely limited by soil water availability. Soil organic matter (SOM) contents have been found to be a reliable index of crop productivity in semiarid regions because it positively affects soil water-holding capacity. Our objectives were to explain differences in wheat (Triticum aestivum L.) yields in response to SOM levels and related properties and to quantify the contribution of a unit increment of SOM content to soil productivity during 1991,1992, and 1994 on a total of 134 production fields in the semiarid Argentine Pampas. Wheat yields were related to both soil water retention and total organic C (TOC) contents in the top layers (0–20 cm) in years with low moisture availability (1992 [r = 0.51, P < 0.01] and 1994 [r = 0.59, P < 0.01]), and were related to both total N and available P contents in a year without water deficit stress (1991 [r = 0.58, P < 0.01]). Wheat yields over all years were linearly related to TOC (r = 0.68, P < 0.01) when these contents were <17.5 g kg. Dependence of wheat yields on soil water retention and on TOC contents under water deficit was related to the positive effect of these soil components on plant-available water. In the absence of water deficit (1991), nutrient availability was the limiting factor. Losses of 1 Mg SOM ha were associated with a decrease in wheat yield of approximately 40 kg ha. These results demonstrate the importance of using cultural practices that minimize losses of soil organic C in the semiarid Argentine Pampas.

Contribution of INTA (EEA Gral. Villegas and EEA Anguil), Univ. Nac. de La Pampa, and Univ. Nac. del Sur.

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