Reducing the Impact of Soil Water Deficits on Soybean Yields in Ontario

Crop Soybean
Start Date2011
End Date2013
Principal InvestigatorEarl, Hugh , University of Guelph
MPSG Financial Support$22,060
Total Project Funding$95,912
ReportFinal-Report-1

Research Objectives

  1. Identify the breadth of variation for water use efficiency (WUE) among commercial soybean varieties adapted to the 2700 heat unit zone
  2. Ascertain how differences in WUE affect variety susceptibility to yield loss under naturally occurring soil water deficits in the field

Project Description

The proposed work is an expansion of a another project looking at the quantification of yield losses associated with water stress under typical Ontario field conditions, and characterization of the physiological basis of those yield losses. This work has supported the hypothesis that “there is always drought stress”, and has indicated that in Ontario this most commonly manifests itself as mild, transient soil water deficits occurring during the grain filling period.  This project is the next phase, which involves comparing existing commercial soybean varieties for their susceptibility to water stress in the field.

Even in years where precipitation appears to be adequate and there are no outward symptoms of water stress, mild soil water deficits developing during the seed-filling stage significantly can reduce yields. One trait that is hypothesized to be beneficial under this type stress scenario is increased crop WUE, (the amount of crop dry matter produced per unit water used). Variation for WUE is already known to exist in the commercial soybean germplasm adapted to Ontario, but these measurements have so far always been made on young (vegetative) plants, and only under greenhouse conditions. This study will determine if variety differences in WUE are associated with differences in susceptibility to water stress-induced yield losses under typical Ontario field conditions. The basic experimental approach is to grow varieties differing for WUE under both naturally-occurring (rain-fed) and continuously water-replete (irrigated) conditions, in replicated small plot experiments.  While there was significant variation for WUE among the varieties tested, we did not find strong evidence that this trait imparted enhanced drought tolerance in the field.  High WUE among these varieties was not associated with soil water conservation, but rather with aggressive growth and somewhat higher rates of water consumption