CONICET | Buscador de Institutos y Recursos Humanos

Argentina is an important producer of soybean (Glycine max L. Merr.), with 83% of the crop being cultivated under no tillage. Yield gaps of up to 2000 kg ha-1 are usually recorded in the main area, even between fields that are at a short distance. Soils are predominantly Argiudolls, with subsurface compacted layers (massive zones without visible macropores, termed delta clods, M). The aims of this work were (i) to identify climatic variables and soil properties that explain seed yield variation in rainfed soybean growing in no-tilled Argiudolls; and (ii) to quantify the relative effect of those soil and climatic variables on field soybean yield. The database, which included 175 cases of soybean crops, was obtained from production fields during four crop seasons, covering a wide range of environmental and soil conditions. Multifactor linear regression was used to assess soybean yield variability and quantify the contribution of climatic and soil traits in the formation of grain yield. Threshold values, such as 180 mm of cumulative precipitation during the whole reproductive period and 200 mm of available soil water at sowing, separated different situations: (a) environments that were above those values, in which 48?51% of total yield variation was explained by mean daily temperate during seed set, cumulative solar radiation during seed filling, combined with soil variables, such as organic matter content and M, or, alternatively, saturated hydraulic conductivity (Ksat); and (b) environments that were below the threshold values, in which precipitation during the whole reproductive period and M or Ksat explained 72?88% of total soybean yield variation. Highest soybean yield values were always attained in fields under good soil physical conditions.

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