Simple biomass production models are used to assess performance of crops under a wide range of environments. The most widely used are based on radiation-use efficiency (e) and water-use efficiency (w). We used a canopy transpiration and photosynthesis (CTP) model to obtain simulated daily values of e and w for maize (Zea mays L.) and wheat (Triticum aestivum L.), and to assess their response to weather variation at eight locations. The modeled daily e fluctuated dramatically in response to weather variability even when crop and soil conditions were kept invariant. In wheat, e correlated negatively to solar radiation, vapor pressure deficit (Da), and Penman-Monteith reference crop evapotranspiration, and positively with diffuse fraction of solar radiation. In maize, the association with these variables was good only over a portion of the range of variation for the variables; when days with average temperature below 25°C were excluded the association was stronger across the entire range. The interactive effect of all variables on e is hard to separate; for both crops, e could vary by up to twofold for a given value of any of the variables. Daily w was inversely related to vapor pressure deficit (maize: w = 10.3D a -0.42; wheat: w = 6.5D a -0.47), showing a stronger association than any obtained for e and without major fluctuations attributable to temperature. The estimated w showed more variability when the vapor pressure deficit was below 1 and 1.5 kPa for wheat and maize, respectively. Daily w was also inversely related to the Penman-Monteith reference crop evapotranspiration; the association with other weather variables was weak. Under water stress w tended to increase, almost preserving unstressed biomass gain until transpiration was reduced below 80% of the unstressed value, with biomass gain decreasing sharply with further transpiration reduction. Overall, this simulation study supports the use of w-based biomass gain models over e-based models.
|Original language||English (US)|
|Title of host publication||Response of Crops to Limited Water|
|Subtitle of host publication||Understanding and Modeling Water Stress Effects on Plant Growth Processes|
|Number of pages||20|
|State||Published - Oct 26 2015|
All Science Journal Classification (ASJC) codes
- Agricultural and Biological Sciences(all)