Crop Time: Degree-day Models and an Online Decision Tool for the Vegetable Industry

Degree-day (DD) models have been used since at least the 1960s. In general they predict development of ectothermic organisms (e.g. plants, insects and fungi) more accurately than calendar days. Many in the tree crops industries have adopted pest DD models to support integrated pest management decisions since the 1990s, but most vegetable growers in the Pacific Northwest do not use DD models to manage crops. Exceptions are sweet corn and garden pea, where DD models have been developed for some cultivars. Small and mid-sized vegetable farmers try to schedule their harvests to supply fresh produce consistently during the market season. Direct market farmers often schedule Community Supported Agriculture pickups or restaurant sales on a weekly basis. Mid-sized wholesale growers also attempt to supply produce on time and in the right quantity. Market share of the top 20 U.S. retailers grew from 39% to 64% from 1992–2009, this consolidation increases pressure on shippers to maintain contracts with customers. They often err on the side of over-production to avoid weather or pest related shortfalls, and improved crop scheduling could help them fill contracts and maintain buyer loyalty. We have developed Crop Time to support vegetable crop management and DD model verification. Threshold temperatures, DDs to harvest and intermediate growth stages have been verified for transplanted broccoli, direct-seeded slicing cucumber, transplanted sweet pepper, and direct-seeded sweet corn cultivars using single sine curves and lowest coefficient of variation. Growth stage descriptions and threshold temperatures are available on the site to invite open sharing of data for future model development. Crop Time is integrated with the Oregon State University (OSU) Integrated Plant Protection website (http://uspest.org/dd/model). The user interface has been modified to facilitate rapid selection of automatic weather stations (AWS) using a custom Google Maps interface. Collaborative networks provide access to data from more than 15,000 AWS in the United States. Model input now allows simultaneous model runs of up to four planting dates to schedule succession plantings. Output formats have been modified to summarize the most useful phenological events predicted by DD models. Educational outreach is provided through the OSU Small Farms website: http://smallfarms.oregonstate.edu/croptime. Usability is being tested to make the website as self-explanatory to new users as possible.