2012 CORN SILAGE HARVEST: WILL YOU BE READY?
Chopping corn at the right moisture level is the most important management factor for making high quality silage. The warm, dry season has caused a range of field conditions and has hastened maturity. Careful monitoring of fields will be important for planning when to harvest. Average monthly temperatures in Chazy have been well above average (3.7 to 11.9 ºF above the 30-yr average). At the end of July almost 2,000 growing degree days (GDD) had accumulated, which is about a month ahead of last year (Fig. 1).
Research by Bill Cox at Cornell showed that a 96-100 day relative maturity hybrid required about 750 GDD from silk/tassel emergence to silage harvest. Using this as a guide, corn that had silked by mid- to late July in NNY could approach ideal silage moisture (65 to 68%) by early September. Earlier planted hybrids could be ready sooner. The actual time until harvest will depend on GDDs in your area, planting date, hybrid, and soil moisture. All else equal, continued heat and dry weather will speed up maturation and dry down.
The bottom line is that you need to monitor fields and check whole plant moisture levels. Local weather data can help gauge your timing with GDD, but the best way to determine where your corn crop is at is to visit the field. Make a note when fields reach the dent stage and start checking whole plant moisture when milk line is ~¼ or less. Remember that kernel milk line is not a reliable predictor of whole plant moisture. This year’s weather may further confound the relationship between kernel milk line and whole plant moisture— it is a good year to start using whole plant moisture as your guide to harvest timing if you are not already doing so.
While sampling individual plants to estimate field moisture status is a good approach, there is room for error. Often there is significant spatial variability in whole plant moisture within a field, especially with changes in topography or soils. Sampling 20 plants from a 10 acre field (at 32,000 plants/ac) means you sampled about 0.006% of the population — room for error, but still better than guessing. The best approach is to chop some guard rows, and if you have a self-propelled machine, chop a swath down the middle of the field to get a more representative sample and then check the moisture level. Taking extra time to fine-tune whole plant moisture will be repaid with the improved quality and milk production potential of your silage.
— Eric Young
Figure 1. Cumulative growing degree days (86/50) at Chazy, NY
(from Chazy Orchards’ weather station).