Crop yield trends in relation to temperature indices and a growth model

Abstract

Annual variability and trends in winter wheat yields were evaluated for relationships to climate in 6 long-term experiments (in total 1915-2005) and regionally in 3 counties in southern and central Sweden. The annual yield was predicted as function of a climate index and year. Alternative indices were used based on either monthly temperatures or yield predicted by a simple weather-driven crop growth simulation model. The main results were as follows. (1) The yield predictions were better for regions than for the long-term experiments. (2) The time variable accounted for more of the yield trend in regions than in the experiments, and more in southern than in central Sweden. (3) The models based on a simple temperature index were often better yield predictors than the growth model. (4) The relations to winter temperatures became gradually weaker after ca. 1970. (5) The yield relation to simple temperature indices differed between locations, similarly for experimental and regional yields. (6) The strongest influence of climate was estimated by means of the growth model predictions of regional yields in Gotland County. (7) The fraction of regional yield trends ; ranging from 57 to 90 kg ha -1 yr -1) that could be attributed to climate was estimated greatest in the Gotland region (27 to 64%). For climate change assessments of winter wheat yield in central Sweden, the growth model considering temperature, radiation and water conditions during spring and summer would also need to include processes of overwintering.

Can Agrometeorological Indices of Adverse Weather Conditions Help to Improve Yield Prediction by Crop Models?

“…The use of frost tolerance models (e.g., [61]) might improve the simulations. Surprisingly, however, for Uppsala, which is located farther north than Lund, the deviations could not be related to winter temperatures, although they are known to influence yield even more than in southern Sweden [57]. The different model performances between the locations, both for extreme temperatures and dry conditions could be caused partly also by the fact that that the same cultivar settings (calibrated on Austrian cultivars) were applied at all sites.…”

“…Specifically, low yields were correlated with the number of arctic days in January. A previous study [57] has found, for basically the same data set, that high yields were related to high February temperatures and were less significantly related to January temperatures, indicating that the relationship of temperature to yield depends on the way in which the effects of temperature on the crop are expressed. The apparent absence of a correlation between yield and number of days with drought in Sweden is in agreement with other studies, which have seldom found clear relationships between the precipitation in specific months from March through June and winter wheat yield in Sweden [58], Denmark [59], and Finland [60].…”

Estimating winter survival of winter wheat by simulations of plant frost tolerance

“…Successful overwintering is a prerequisite of high winter wheat yields. This is indicated by the relationship between observed yield and winter temperature in several studies, as for instance in the northern cultivation areas of winter wheat in Sweden (Eckersten et al., ; Elmqvist & Arvidsson, ), the United Kingdom (Landau et al., ) and in the southeastern part of the Czech Republic (Kolář, Trnka, Brázdil, & Hlavinka, ). Winter survival of wheat is affected by a multitude of factors associated with genotype, plant vigour and the occurrence of biotic and abiotic stress factors.…”