Staging Corn Maturity for Harvest

Corn field

Is your corn ready?  Planting was staggered this year and maturities are following suit.

Sixty days, that’s the length of time, on average, that it takes for corn silage to mature from silking (pollination) to black layer (physiological maturity). We use 1/2 milk line as the indicator to start checking whole plant moisture.

This year dry matter measurements are running dryer than milk line would typically indicate. At 1/4 milk line, DM measured 65% which we would normally expect at 1/2 milk line.

Seventy percent moisture is the long-term accepted target for beginning harvest, but consideration needs to be given to your farm storage. It’s a fine balance to achieve a DM where you can pack well while preserving maximum nutrients. Bunk silos pack better at the top of the range, while uprights may have excessive seepage above 68% moisture (see Table 1). Nutritionists are also encouraging targeting higher dry matters to increase starch levels.

Table 1. Target Corn Silage DM Levels for Vertical Silage Systems
Oxygen Limiting Structure
Corn Silage 40-65% DM    [35-60% moisture]
Conventional Concrete & Stave Structure
Corn Silage
    Under 60 feet 32-36% DM    [64-68% moisture]
    Over 60 feet Increase 2% DM per 10 ft vertical height
Source: Mike Hutjens, University of Illinois, Urbana
http://qualitysilage.com/wp-content/themes/twentyten/PDF/TowerSiloManagement.pdf

Whole plant dry matter samples will run 2 – 3 points above actual field conditions (aka field will be wetter). Knowing the maturity of your crop and how many days or weeks it takes to harvest allows you to target the moisture for beginning harvest (see Table 2). Moisture will decrease by 0.5 – 1.0 points per day, depending on the weather conditions.

TABLE 2. Influence of Corn Maturity on Grain Yield, Whole Plant Silage Yield, and Moisture Content
     

% Max Yield

% Moisture

Maturity Stage  Avg cal Days To Maturity

 GDU to Maturity

Grain

Whole Plant

 Grain

Whole Plant

Silk

50-55

1100-1200

0

50-55

80-85

Blister

40-45

875-975

0-10

55-60

85-95

80-85

Late Milk

30-35

650-750

30-50

65-75

60-80

75-80

Early Dent

20-25

425-525

60-75

75-85

50-55

70-75

Full Dent
(1/2 Milkline)

 10-15

200-300

 90-95

 100

 35-40

 65-70

Blacklayer

0

0

100

95-100

25-35

55-65

Assumes 20 GDU/day to maturity.
Adapted from Carter, P.R. 1993.  Pioneer Hi-Bred International, Inc.