Phenological responses of spring wheat and maize to changes in crop management and rising temperatures from 1992 to 2013 across the Loess Plateau

The observed historical changes in crop phenological events are not only as a sensitive indicator to temperature variations but also the consequence of agronomic management such as adjustment of sowing date, cultivar selection and innovative farming practices. Clarifying how these factors influence crop phenology is of paramount importance in understanding/implementing adaptation strategies to future climate change. Changes in phenophases of dryland spring-sown wheat and maize were investigated using the observed phenological data from 1992 to 2013 across the Loess Plateau. Using a series of phenological growth models, we illustrated that once the varietal effect was fixed, rising temperature alone produced a general advancement on dates of heading and maturity, leading to a significant shortening of the vegetative phase (5.2 days decade−1 in wheat and 1.1 days decade−1 in maize), a shortened duration of reproductive phase (0.9 and 2.0 days decade−1 respectively) and the length of whole growing season (6.1 days decade−1 in wheat and 3.0 days decade −1 in maize). In contrast, cultivar shifts prolonged the reproductive duration and the growing season length by 2.2 and 4.7 days decade−1 for spring wheat, and 3.3 and 1.5 days decade−1 for maize, respectively. The continuous update of cultivars during the past two decades has offset 63.5% of the shortening effect of growing season length caused by rising temperature for both crops. Our data indicate that adjusting sowing date and shifts to longer season cultivars are the critical adaptive strategies to cope with temperature increases in dryland spring-sown wheat and maize in the Loess Plateau or regions with similar environments.