Title
Trends in planting date and growing season for crops
Authors
Beth Drewniak Argonne National Laboratory
Abstract
The seasonal cycle of crops is strongly influenced by climate. For example, planting date is determined by thresholds of temperature and precipitation, thus allowing the day of planting to change from year to year. Crop productivity and yield are affected by temperature and precipitation during the growing season. The length of the growing season is driven by temperature, since crops phenological development is determined by heat accumulation. Crops have optimum temperature thresholds that limit growth during periods of excessive heat or cold. Because the total number of heat units needed for maturity is semi-fixed for crops, warmer years result in shorter growing cycles, and therefore lower yields as less time is spent during grain development. Furthermore, lack of adequate moisture can have dire consequences on yield. Understanding how changes in climate lead to changes in the seasonal cycle of crops is critical for crop yield estimation. In this study, the new planting date calculator in ELM is tested with global crops to identify possible trends in planting date and the length of the growing season over the historical period. Furthermore, correlations between these, and other variables such as temperature and precipitation over the growing season, and yield are evaluated.
In addition, in the current ELM, growing season for crops is capped by a maximum number of heat units, which is not ideal for all regions. This is particularly true in low latitudes where ideal conditions exist for longer growing seasons but tend toward earlier harvest in the model. Therefore, a sensitivity study is included to look at the impacts of loosening the cap on heat units, to examine the impact of longer growing season on yields. This is a simplistic proxy for representing different cultivars to exist in different regions.