Now is the Time to Begin Evaluating Corn Fields for Harvest

Joe Lauer, Wisconsin Corn Agronomist

For most corn fields in Wisconsin, pollination and the “lag” phase of kernel development is wrapping up and we are in a “linear” phase of development where kernels are accumulating 4-6 bu/A per day. The grain filling period of corn lasts approximately 60 days (Figure 1). The “lag” phase starts with the kernel ovule fertilized by pollen and for the next 7-10 d cell division occurs in the endosperm. The “linear” phase is most important for yield and lasts about 40 days.

For a 200 bu/A yield level, starch accumulates in the kernel endosperm at the rate of 5 bu/A per day during this phase. The grain filling period ends with a 7-10 d “maturation” phase when the kernel moves from 50% kernel milk to the black layer stage. During grain filling most management options are no longer available unless irrigation is available when water and N can be applied during the first half of grain filling.

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