Impacts of climate change and crop management practices on soybean phenology changes in China

Crop phenology is determined by both climatic factors and agronomic management practices such as sowing date and cultivar characteristics. Exploring the interactive effects of climate change and crop management practices on crop phenology can be used to devise adaptation strategies to mitigate climate change. The objectives of this study were to: 1) examined trends in soybean (Glycine max L.) phenological development in China from 1981 to 2010; 2) isolate and quantify impacts of climate change and crop management on changes in soybean phenology; 3) determine the relative contribution of climate change and crop management to observed changes in soybean phenology; and 4) determine the relative contribution of temperature, precipitation, and sunshine hours to changes in soybean phenology. Changes in soybean phenology were observed across the major soybean producing area of eastern China during 1981-2010. Observed dates of sowing, emergence, anthesis, and maturity were delayed by an average of 1.78, 0.83, 0.19, and 0.62 days decade^-1, respectively. Additionally, the lengths of the vegetative growth period and the soybean growing season were shortened by an average of 0.62 and 1.16 days decade^-1, respectively. Conversely, the reproductive period was lengthened by an average of 0.43 days decade^-1. Crop management practices had greater influence on sowing, emergence, and maturity dates than climate change. The direction of the changes to phenology trends created by management and climate change were opposite to each other. The relative influence of climate change on dates of anthesis, lengths of the vegetative and reproductive growth periods and growing season was larger than the influence of crop management practices. Mean temperature was the dominant climatic factor influencing most soybean phenological stages and phases. Delayed sowing dates and use of longer-duration cultivars are management adaptations that farmers have used to adapt to climate change occurring in past decades and that can continue to be used. These results indicate that farmers have a wider sowing window in spring and can select cultivars with long growing season duration and frost-tolerance to mitigate detrimental effects of a future warmer climate.