MidWeek Review
HAVE. TO. KEEP.
PUSHING.
Are we
there yet?
HELP!!!
I think we lost
our neighbor…
Almost there!
Okay, so that might be a lyric from an old country song that doesn’t really have anything to do with corn, but it’s the only
reasonable quote that had the word “stand” in it…. But now that I have your attention, it brings up the theme for this week:
evaluating corn stands. I know, it’s hard to imagine right now, but the day we start to see corn (and soybeans) spiking through
the ground will be here before we know it! It’s an important point to refresh our memory on as we start estimating yield
potential (and hopefully not replant decisions).
Accurately determining plant stands help identify planting
successes and challenges that may have occurred, and
help prevent them from occurring next year. For me, it’s
about evaluating the likelihood of successfully reaching
my yield goal. Simply, using the knowledge of row widths
and a tape measure can detect possible problems. The
1/1000th of an acre technique is the quickest way to
measure plant populations (but maybe not the most
accurate representation of yield potential, we’ll look at
another way on Page 2). It’s simple, just measure 1/1000th
of an acre based on your row width & count the number
of plants in that length of row. Multiply the number of
plants by 1,000 to get plants per acre. The more your
repeat, the more accurate it is.
Keep in mind it takes 100-120 GDD’s to get corn to
emerge, and 3-4 days after that to have V1 corn with a
fully-visible collar. 7-10 days after that, we will see V2
corn at about 200 GDD’s, and V3 will hit 10-20 days after
emergence, or about 350 GDD’s. The R7 Tool has a great
weather portion that will help you keep track of where
GDD’s are at for your field!
Corey Evans |
Technical Seed Manager
MidWeek Review
(Red): all plant
spacing’s are
identical (8”), and the
standard deviation =
0 (perfect)
(Blue): standard deviation =
3”, meaning the majority of
the plant spacing’s are within
+/- 3” from average.
Imagine this… You have 17’ 5” of row representing 1/1000th of an acre, and you count the number of corn plants in that
section. There is 35, multiplied by 1000, gives you a plant population per acre of 35,000, which is exactly what was
planted! Great! Except, in that 17’ 5”, there is 6 skips & six double plants. Does that have the same yield potential that 35
evenly spaced plants would have?
Taking the stand deviation allows you to measure consistency of plant spacing. Simply, stand deviation measures the
distance, in inches, a majority of plants are from the average plant-plant spacing. For example, if the standard deviation in
a population count is 2”, it means that 2/3 of the plants were within 2” of the average plant spacing (average would be 6”
in 30” rows, so 4-8”). Don’t count a plant that is more than 2-leaf stages behind the average growth stage since it will act
like a weed instead of contributing to yield. 2” is usually the spacing uniformity goal we strive for given our planter
technologies today. Yield loss observed over university studies range from 1.2 to 4.5 bushels per acre per inch of standard
deviation due to some corn plants becoming a “weed” and stealing nutrients/water/light from the neighbor, or the impact
of skips and bare soil. Even though not much can be done to mitigate the stand problem today, it allows growers to
evaluate their planting operation by understanding what’s causing the gaps and doubled up plants (and future problems).
Is seed present? Variable planting depth? Poor seed-to-soil contact? Pests? Stand deviation data can drive insights on
planting efficiency and potential problems to manage the rest of the season. Contact your WinField United representative
to get a Standard Deviation Excel Worksheet!
Estimating soybean plant population offers a few different approaches, but the
table above shows the “plants per foot of row” method. Measure 1-12 feet of
row, count the number of plants in each foot section, take the average per foot
of row and use the chart to reference and estimate average plant populations.
Corey Evans |
If you are digging up corn seed before it
emerges and you don’t want to uncover 17+
feet of soil, use the above table to get a quick
reference of average spacing between kernels
to estimate plant population per acre!
Technical Seed Manager
MidWeek Review
When we are talking plant stands and yield potential, we have to talk about RTP (Response to Population) scores. Remember, a
high RTP score shows a hybrid’s potential yield gain with increasing populations. A medium RTP score defines a hybrid as able to
achieve high yields at moderately high populations, yet still maintain yield at moderately low populations. A low RTP score
indicates a flex-ear-type hybrid with acceptable yield potential, even at low populations. In the AnswerPlot, we derive the scores by
planting products at a high & low population (usually 30k and 38k), and measure the change in yield to derive the score. The
greater the change in yield, the higher the score. You can find these scores via the R7 Tool, in the Top Ten application. When you
are looking at plant stands, and you run across a few areas that plant stands decreased, reference the RTP scores to understand
what the potential yield implication may be. The higher the hybrid’s score, the higher the risk for yield potential loss due to less
than desirable stands! Think about how your crop’s yield potential impact’s all of the other applications the rest of the year! This a
simple process, but it’s a crucial data point! Last year, our AnswerPlot data showed getting population right was worth 10 bushels!
Be mindful of this as we start to rush to get the crop in the ground with improving conditions. If the ground is still not quite fit, but
you’re ready to plant, understand the yield potential risk if you’re willing to sacrifice stand counts and you are using a high RTP
product!
Corey Evans |
Technical Seed Manager