Corn kernels continue to accumulate seed weight until physiological maturity is reached.
Hard starch begins forming at the kernel tip when denting occurs. This hard starch layer gradually progresses to the kernel base over the next 20 days. This progession is very important to irrigation scheduling. The milk line is the borderline between the bright, clear yellow color of the seed coat outside the hard starch layer, compared to the milky, dull yellow of the hard dough layer. An abscission layer forms when the hard starch layer reaches the kernel base.