Certified Crop Advisor Practice Exam

Growing degree days are not particularly useful in deciding when to _________.

1. fertilize

2. irrigate

3. harvest

4. plant

The correct answer is: irrigate

Growing degree days (GDD) are a measure used primarily to predict plant development rates for crops, based on accumulated heat units during the growing season. This metric is particularly useful in understanding and forecasting crucial growth milestones such as flowering, maturity, and harvesting times. While GDD can provide insights into plant readiness for harvest or optimal planting times, it is less directly correlated with irrigation decisions. Irrigation is typically based more on immediate soil moisture levels, rainfall patterns, and water availability rather than the thermal accumulation used by GDD. Therefore, while understanding the temperature conditions and growth stages can inform decisions on when to plant or harvest, the need for irrigation usually relies on crop water requirements and environmental conditions rather than accumulated heat units. In summary, since GDD primarily informs growth stages rather than moisture needs, it is not particularly useful in deciding when to irrigate.