Research and IPM

Phenology Model Database

Alfalfa Harvest

Using a 3-cutting management system

Phenology models predict timing of events in an organism's development. For many organisms which cannot internally regulate their own temperature, development is dependent on temperatures to which they are exposed in the environment.

Note: Before using a model that was not field tested in your location, you should test the model for one or more seasons under your conditions to verify that it will work for you.

Model 1 of 2

Sharratt, B.S., C.C. Sheaffer, and D.G. Baker. 1989. Base temperature for the application of the growing-degree-day model to field-grown alfalfa. Field Crops Research 21: 95-102.

Location of study: Rosemount and St. Paul, Minnesota (field studies)

Developmental threshold

Lower	DD (°F)	DD (°C)
Spring	38.3°F	3.5°C
Early summer (June to mid-July)	45.5°F	7.5°C
Late summer (mid-July to late August)	50.0°F	10.0°C

Method of calculation: Max-Min Method: Degree-days = [(Tmax - Tmin)/2] - To, where Tmax is the daily max temperature, Tmin is the daily min temperature, To is the lower threshold. Set Degree-days to 0 when To > (Tmax - Tmin)/2.

Degree-day accumulations required for each stage of development

Biofix: For spring period, last occurrence of 27°F (-2.8°C) or lower; for summer periods, harvest.

Model 2 of 2

Sanderson, M.A., T.P. Karnezos, and A.G. Matches. 1994. Morphological development of alfalfa as a function of growing degree days. J. Prod. Agric. 7:239-242.

Authors' conclusion states "relationships among MSW [mean stage by weight] and GDD in alfalfa differed among locations, years, seasons, and cultivars. Because of these differences, a broadly applicable equation for predicting morphological development (MSW) from GDD may not be possible."