#24 New method to trigger plant date for crops in ALM

Abstract

Current crops in ALM are restricted to temperate latitudes because the planting date is determined by a temperature threshold that is not appropriate for use in tropical zones. Tropical regions typically have temperature ranges that can support crop production year-round; however, the limiting factor in many regions is water availability, making precipitation the driver for planting.  A new plant scheme that takes into account temperature and precipitation seasonality will be needed to determine plant date. The more robust plant date in ALM will meet two requirements: 1) the plant trigger will function globally, and 2) the plant date can change over time. This will be accomplished by establishing the seasonality of a region from long term coefficient of variance of temperature and precipitation. For regions with temperature seasonality, plant month will be determined the month that the exponential weighted moving average temperature exceeds a threshold (dependent on crop type) and the actual plant date will be determined the day of the month the 10-day average soil temperature exceeds a threshold (dependent on crop type). For regions with precipitation seasonality, plant month will be determined at the beginning of the largest 4-month sum of precipitation to potential evapotranspiration ratio. Then, the actual plant date will be the first precipitation event of the month. For regions that have temperature and precipitation seasonality, seasonality classification will be determined by the average temperature of the coldest month.  Regions where the temperature of the coldest month exceeds 10 degrees Celsius will be considered precipitation seasonal, and temperature seasonal otherwise. For regions that have no seasonality, an arbitrary plant date will be chosen. Some of the benefits of the new plant method is there is no need for external data and planting date can evolve over time with changing climate conditions.