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LATE CORN REPRODUCTIVE STAGES

08/28/2018
MATURITY AND YIELD ESTIMATION
  • Corn pollination is complete and had occurred with minor issues.
  • Continuation of favorable warm weather and adequate moisture promises speedy corn maturation.
  • Checking corn yields can be quick and simple with the updated FS Yield Estimator App.

Most areas saw uneventful corn pollination this season.Although temperatures were warm during this time period, moisture levels were adequate and the crop was able to complete the pollination process with little difficulty. With corn nearing or close to the late reproductive stages, now is a good time to discuss those briefly.

Dent Stage (R5) – Under optimum growing conditions, corn will normally start to develop depressions or dents in the kernel crowns about four to six weeks after silking.This is the “dent stage” (R5) and signals a rapid starch accumulation in the kernels.At this point, and for the next 20 days or so, a distinct line begins to form, starting at the crown of the kernel and progressively moving toward the tip.This is referred to as the kernel milk line.The milk line marks the division between the starchy part of the kernel and the softer, milky part of the kernel (Figure 1). Literature indicates that total plant death at the beginning of the dent stage will reduce final yield about 40 percent. Total plant death at about half milk line will reduce yields about 12 percent. Note: Milk line in kernels is often used to schedule corn silage harvest.Severe stress during milk line movement in the kernel will often cause this line to disappear as normal starch accumulation is halted.

Physiological Maturity (R6) – Maximum accumulation of starch in the corn kernel marks physiological maturity, which normally occurs 8 or 9 weeks following silking. Black layer formation at the tip of the kernel follows rapidly (Figure 2). At this point, the corn is more-or-less safe from frost or other stress factors, although physical damage can still greatly impact yields.Grain moisture at R6 usually will range from 25 to 40 percent.If the plant is still healthy, it will actively draw moisture from the ear and harvest moisture will be reached more rapidly.Impairment of plant health, stalk damage, disease or other serious problems will slow the physiological removal of moisture from the ear and the grain will have to “air dry”. According to literature once corn has reach R6, roughly ½ to ¾ of a point of moisture can be drawn out of the kernels per day, however, as stated earlier if the plants experienced more disease, and stalk damage then that dry down may be longer.

Estimating Yields Before Harvest – Corn yield estimates have become rather simple with the help of yield estimate apps like the FS Yield Estimator App (Figure 3). Simply measure out 17.4 ft of row in several spots in a field. This measurement represents 1/1000th of an acre. Count off the number of plants with an ear of corn on them and record that for your Plant Population. Next, the Kernels portion is the number of kernels per bushel at 56 lbs/bu, typically research shows you should use 90,000 kernels for an average. Collect 3-5 ears in those spots where you took stand and count off the number of rows around and the number of rows long and insert it into the app. It is always good to have more ears than less; this will give you a more accurate reading of what yield the grower could expect.

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