During harvest time, the question of harvest order may not always be straightforward. While weather, equipment, and other factors always come into play, plant health is an important aspect to consider.
To get an idea of what fields to go for first, we probably all begin with planting date and comparative relative maturity (CRM), sometimes referred to as days-to-maturity. CRM gives us a sense of which corn to check for harvest maturity first, and it also tells us how many fields might be ready at the same time. This is a great starting point because it also lets us know which corn will become vulnerable to late-season diseases and extreme weather events the soonest. Fields planted early and/or with a short CRM will typically mature first, after which they will no longer be protected by many chemical and structural defenses that a plant uses to prevent disease when alive. At this stage, plants are more susceptible to breakdown by pathogens and opportunistic fungi that simply take advantage of dead tissue.
The other bit of information to recall is hybrid selection. This choice that was made almost a year prior now comes into play when traits like stalk strength, resistance to disease, husk cover, and ear orientation are considered. Standability can be affected by anything that robs the plant of its ability to maintain good stalk structure beyond its maturity, for example, nutrient deficiencies, drought, root and stalk rots, and foliar diseases that prevent photosynthesis during grain fill. When growers choose hybrids with high breeder ratings for stalk and foliar disease resistance, stalk strength, and drought tolerance, they select traits that will keep plants upright longer into harvest season.
Ear disease resistance and physiological traits should also be considered. Ear rots are a serious threat to yield and grain quality as they may affect test weight and be associated with mycotoxins. Even if the ears are free of mold approaching maturity, ear tips that are exposed from the husk because of hybrid physiology or insect damage will be more susceptible to fungal infection as harvest wears on. Similarly, ears that naturally turn downward upon maturity will shed water more readily than those that stay upright and provide a less conducive environment for fungi to grow.
Source : psu.edu