One approach to predicting corn maturity with GDD’s is to monitor GDD’s from planting to harvest and some seed brands provide estimates of GDD’s needed for different hybrids. For corn, the 86/50 method is used for calculating GDD’s, this references a base temperature of 500oF and a maximum of 860oF.
Considerations to keep in mind:
- The numbers provided for a hybrid are often from planting to physiological maturity (black layer) which is past the silage stage. A rough rule of thumb is to subtract 150 GDD’s from this number to estimate the number needed for silage harvest.
- Studies have shown a fair amount of variation in the GDD’s required from planting to silking, which could be exacerbated by the drastic temperature swings experienced in the spring of 2020.
o Figure 1 demonstrates the variability of whole plant dry matter with data from the Northeast Corn Silage Consortium for a group of hybrids planted across multiple locations in the northeast.
Data for three hybrids grown across multiple locations, illustrating the lack of correlations between whole season growing degree days and whole plant dry matter at harvest.
Research in NY by Dr. Bill Cox assessed the number of GDD’s required from silking to silage harvest timing in a multi-year study. While there is still some variability in GDD requirements from silking to silage harvest timing, this method offers better results than using full season numbers as it takes out the early season variability of GDD’s needed from planted to silking. The average GDD’s reported in the study are shown in Table 1.
Approximate Growing Degree Days needed from silking to silage harvest
|Hybrid Relative Maturity||GDD’s (86/50)|
|<96||750 or slight less (extrapolated)|
This study used 32 percent whole plant dry matter (DM) as the target for silage harvest; however, a better target is 35 percent whole plant DM. Therefore, the GDD targets reported in the study offers a sort of early warning for harvest. Once corn begins the dry down process an average rate of dry down is 0.5 percent per day (with a range of zero to one percent per day) indicating that the crop may reach 35 percent DM approximately 6 days after reaching these GDD targets for 32 percent DM.
When a field reaches these GDD targets, it is a good time sample fields and dry down samples for whole plant DM to further refine harvest timing.
Resources for Forage Management in a Drought
Rainfall continues to be very variable around the state. Overall crops seem to be faring pretty well, even in the drier areas; however, many are surely at a tipping point and will begin showing stress soon if rain does not materialize. PRO-DAIRY and Cornell Cooperative Extension have curated resourcesthat may be helpful.
Financial and environmental assistance planning grants are available through the Dairy Advancement Program (DAP). DAP is designed to enhance long-term viability of New York dairy farms while maintaining a commitment to environmental stewardship.
Eligible projects assist New York dairy farmers to position their farm for long-term economic and environmental sustainability. Funds are used to engage specialists for financial analysis and to create business plans, to establish an advisory team, and to develop farmstead environmental plans, including design of practices outlined in the farm comprehensive nutrient management plan. DAP covers 80 percent of the project cost. The farm pays 20 percent, and any amount exceeding value of award.
Up to $5,000 available (for small to midsize dairy cattle farms). Projects include:
- Implementation of a new recordkeeping system (e.g. QuickBooks, DC 305)
- Business planning
- Operational planning
Up to $3,000 for farms who wish to implement an advisory team for the first time. Project includes:
- A team of advisors to assist with improvement in specific areas of farm performance
Up to $10,000 available. Projects include:
- Comprehensive Nutrient Management Plans (update or new) for dairy cattle farms under the medium CAFO size.
- Design of eligible best management practices (e.g. a waste storage, VTA) for dairy cattle farms or heifer boarding operations under the large CAFO size.
Business planning funds are provided by the NYS Department of Agriculture and Markets (augmented by additional funds from Chobani). Environmental planning funds are provided through the NYS Department of Environmental Conservation and the Environmental Protection Fund. The program is coordinated through Cornell PRO-DAIRY and delivered to farms in partnership with Cornell Cooperative Extension (CCE) and agriservice professionals.