Why Your Planting Date Matters: How Event Logging Drives Your GDD and Water Balance Data
Every canola site currently running in the OCM dashboard shows a dashed "Planted" line on its growing degree day and water balance charts. That line comes from logging a planting date against the site, and it is the anchor point both of those figures are calculated from. Get the date wrong, or skip logging it altogether, and the season progress numbers built on top of it stop meaning much.
This guide covers what happens when you log a planting, why the date itself matters, and how to keep the log accurate as the season goes on.
What Happens When You Log a Planting
Logging a planting date and crop against a site creates the reference point everything else is measured from. Growing degree day accumulation and water balance since planting both start counting from that date, rather than from an arbitrary point in the season or the start of the calendar year.
Why the Date Itself Matters
GDD accumulates daily from the planting date, so a date entered a week early or late shifts the whole season's progress figure, including comparisons against a typical maturity range for the crop. The same applies to water balance since planting, which nets rainfall against reference evapotranspiration from that same date. An inaccurate planting date does not just affect one number, it quietly shifts every figure calculated from it.
A planting date that is off by even a few days can shift GDD accumulation and water balance figures enough to change how a site compares against another site, or against a typical maturity range for the crop.
Field Events Beyond Planting
The water balance chart also carries an events layer alongside rainfall and reference evapotranspiration, so the log is not limited to a single planting date per site. Other field events logged through the season appear as their own markers, giving the chart more context than rainfall and evapotranspiration alone.
Reading the Planted Marker on Your Charts
Look for the dashed vertical line labelled "Planted" on both the GDD and water balance charts for a site. Everything to the right of that line is what is being measured as season progress. If the line is sitting in the wrong place, the since-planting figures next to the chart will be measuring from the wrong starting point.
Keeping the Log Accurate Through the Season
A few habits keep the underlying data reliable:
Log the planting date as close to the actual planting event as practical, rather than backdating it later in the season
If a date was entered incorrectly, correct it from the site page rather than leaving it and mentally adjusting the figures yourself
Log other significant field events as they happen, so the water balance chart reflects what actually occurred on site through the season
Frequently Asked Questions:
Where do I log a planting date?
Planting dates are logged against each site, with edits to an existing planting made from that site's own page in the dashboard.
What happens if I log a planting date after the season has already started?
GDD accumulation and water balance since planting both begin counting from whatever date is logged, so entering the date late will produce figures measured from that date rather than from when the crop was actually planted, until the record is corrected.
Can I log more than one field event per site?
Yes. The water balance chart carries a separate events layer alongside rainfall and evapotranspiration, so field events beyond the planting date can be recorded and shown on the chart.