R1 begins when any silks are visible outside the husks, figure 36. Pollination occurs when the falling pollen grains are caught by these new moist silks. A captured pollen grain takes about 24 hours to grow down the silk to the ovule where fertilization occurs and the ovule becomes a kernel. Generally 2-3 days are required for all silks on a single ear to be exposed and pollinated. The silks will grow from 2.5-3.8 cm (1-1.5 inches) each day and will continue to elongate until fertilized.
The R1 ovule or kernel is almost completely engulfed in the surrounding cob materials (technically termed the glumes, lemmas and paleas) and is white in color on the outside. The inner material of the R1 kernel is clear and has very little fluid present. The embryo or germ is not yet visible when dissected with a razor blade (see figure 37). The shank and husks attain full size between the R1 and R2 stages.
Figure 37 displays (from left to right) the R1 kernel (1) with surrounding materials, (2) without surrounding materials, and (3) sliced through the middle to reveal the inner material. Figure 38 reveals the presence of silk hairs which help catch the pollen.
Management Guides - R1 Stage - Silking
The number of ovules that will be fertilized is being determined at this time. Ovules that are not fertilized will not produce kernels and will eventually degenerate.
Environmental stress at this time causes poor pollination and seed set, especially moisture stress which tends to desiccate the silks and pollen grains. Stress will usually result in a nubbin, an ear with a barren tip.
Watch for corn rootworm beetles feeding on the silks and treat if necessary.
Potassium uptake is essentially complete, and nitrogen and phosphorus uptake are rapid. Leaf analysis for nutrients in the plant at this stage is highly correlated with final grain yield and yield response to fertilizer applications.
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