Corn Growth Stages
Growth stages are bundled in two categories: Vegetative growth stages and Reproductive stages. As I describe each of these stages I will put them into perspective of how timing, watering and temperature can affect the final yield.
Vegetative Growth Stages
The Vegetative Growth Stages consist of the Emergence Stage, the Leaf Stages and the Tasseling Stage:
· Emergence Stage (VE)
· nth Leaf Stage (Vn)
· Tasseling Stage (VT)
Emergence Stage (VE)
During this stage most of the growth remains below the soil surface. This protects the seed from potential late frost. Soil moisture is important but more importantly is the timing of the planting, the later the planting the lower the yield potential. Below is a chart of general planting dates. These dates will vary as you move north and south of the Corn Belt.
|
Effect of Planting Dates on Corn Grain Yield | ||
|
Planting |
Yield (%) |
|
|
Date |
Potential |
|
|
1-May |
100 |
|
|
5-May |
97 |
Good |
|
10-May |
94 |
Planting |
|
15-May |
91 |
Range |
|
20-May |
88 |
|
|
25-May |
86 |
|
|
30-May |
83 |
|
Leaf Stages (Vn)
The leaf stages are based on the number of leaves (n) on the corn plant. Each leafing stage carries its own significance, I have selected the leafing stages that represent tipping points in the plants potential yield.
V5 – Occurs 14 days after Emergence. Cooler soil temperatures will delay the plant from reaching this stage as well as delaying tassel formation. It will not affect yield, it could lead to a late harvest and a potential of frost damage before harvest.
V9 – Occurs 28 days after Emergence. Flooding at this or earlier stages is a concern as it can kill the plant within a few days. Flooding at later stages is less detrimental because most of the growing is above ground.
V15 – Occurs 56 days after Emergence. Moisture is critical from the V6 – V15 stage. Extended drought can reduce the yields by as much as 25%.
Tasseling Stage (VT)
The tassel is completely visible when the plant has reached its full height and will begin to shed its pollen. Hail damage is more serious at this time than any other growth period.
Reproductive Growth Stages
There are six stages to the Reproductive Growth Stages:
· Silking
· Blister
· Milk
· Dough
· Dent
· Maturity
Silking (R1)
Occurs about 3 days after the Tasseling Stage. Silk is visible outside the husk. Falling pollen grains are captured by the silk and grow down the silk.
Blister (R2)
Occurs 10 – 14 days after Silking. Between the final growth stage and Blistering moisture is critical. Drought conditions can reduce yield potential by as much as 50%, or 6% per day during a drought.
Milk (R3)
Occurs 20 days after Silking. Stress effect is less now. Kernels are beginning to yellow outside and contain a milky white inner fluid (80% moisture level).
Dough (R4)
Occurs 26 days after Silking. Kernels begin to gain in dry weight and size and have a ‘doughy’ consistency. An early frost at this stage can be detrimental to the crop with a potential loss of 50%.
Dent (R5)
Occurs 36 days after Silking and should finish about 48 days after Silking. The kernels begin to dry and have a dented appearance. Stress at this point will reduce kernel weight but not kernel number. Frost is the major concern because it can stop dry matter accumulation and cause premature black layer formation, reducing yield.
Maturity (R6)
Occurs 55 days after Silking. All kernels have attained maximum dry weight. Husks and many leaves are no longer green.
|
Corn Grain Frost Injury Yield Reduction |
||||
|
Kernel |
Kernel |
Days after |
Days to |
Yield |
|
Development |
Moisture |
Silking |
Maturity |
Reduction |
|
Dough |
70% |
26 |
31-37 |
35-50% |
|
Dent |
50% |
36 |
20-23 |
10-20% |
|
Mid-Dent |
40% |
48 |
10-12 |
4-5% |
|
Maturity |
30 - 35% |
55 |
0 |
0% |
|
Critical Points of Growth |
||
|
Tipping |
Time from |
|
|
Points |
Emergence |
Concerns |
|
V3 |
9 - 12 |
Late frost will not damage plant potential yield |
|
V5 |
14 - 21 |
Cooler soil temperatures will slow growth, potential for late harvest |
|
V9 |
28 - 35 |
Flooding up until this stage can kill a plant in a few days |
|
V15 |
56 - 63 |
Drought conditions from V6 - V15 can reduce yields up to 25% |
|
Tasseling (VT) |
60 - 67 |
Water is still critical and hail can lead to pollen damage |
|
Silking (R1) |
63 - 68 |
Water is critical |
|
Blister (R2) |
73 - 78 |
Drought conditions from V15 - Blister can reduce yields up to 50% |
|
Milk (R3) |
83 - 88 |
Water is critical |
|
Dough (R4) |
89 - 94 |
Frost can reduce yields by 35 - 50% |
|
Dent (R5) |
99 - 104 |
Drought conditions from Blister - Dent can reduce yields up to 25% . Frost can reduce yields by 4 - 20% depending on level of dent |
|
Maturity (R6) |
118 - 123 |
|
References:
http://weedsoft.unl.edu/documents/GrowthStagesModule/Corn/Corn.htm#
http://www.ag.ndsu.edu/pubs/plantsci/rowcrops/a1173/a1173w.htm