Dave Jones
Director - Agronomic Services

Agronomic Update

July 17, 2008

Mid-season Development Based on Degree-Days (Heat Units)

In the last Agronomic Update, we discussed degree days/heat units and how they are calculated and used to determine crop development.  Then we reviewed how the crop stood on July 1st.  So let’s further review how crop development is progressing at this time.  Below is a table comparing the 2008-growing season (based on degree-days) to the 25-year average.

Table 1.  Degree-days based on 2008 and the 25-yr average weather data for 3 planting dates and four locations.

July 1st, we were pretty close to the 25-yr average at all three planting dates in Glenn, Colusa, and Sutter counties, while Butte county lagged a bit behind. Glenn, Colusa, Butte and Sutter counties were +5.9, +3.4, - 0.9, and +2.8 heat unit days, respectively, different from the 25-yr average, at that time. As of July 15th those numbers are +6.6, +4.5, -0.6, and +3.9 for Glenn, Colusa, Butte and Sutter counties, respectively.  So you can see, from July 1st until now, all areas have progressed at just about the 25-yr average rate, still holding a slight lead over average except for Butte county which is essentially right at average as of July 15th.