Monday, July 7, 2014

2014 is Back to Normal

It is early July and the normal questions are coming in.
Why are the soybeans yellow? Why does my corn have tillers?
In these parts of south Perth county, June was much kinder than May.  Bill Arthur provides heat unit records to me, which he has been collecting for over 30 years.  His temperature data shows that 2014 is a very good example of average with respect to heat.  Heat unit accumulation to the end of June is very close to the 30 year average, which for these parts is within an eyelash of 1000 heat units.  It is easy to tell this is a typical year because corn is now anywhere from mid-thigh to shoulder and on the fast track to tassel by the end of this month.

Corn planted during the last week of May did not get the full benefit of this heat, but as I have explained before late planted corn makes up the difference by advancing quicker through the vegetative growth stages.  The later planted corn is more uniform on average than earlier planted corn which has an additional positive effect on yield for the later planted fields.  The 45 mm of rain received  in June is half the normal amount, but still more than adequate to sustain early growth.  Life is good.

Soybeans are going through a normal yellow stage of growth.  This year the condition is a little more pronounced than average, but not a significant cause for alarm.  It is a transition period before flowering really starts to commence.  The plant is experiencing rapid growth but the nitrogen fixing nodules have not kicked into high gear yet.  The yellow fades within a few days.
There has been some chatter this week about applying nitrogen to soybeans. I have witnessed before the effects of nitrogen availability on early growth.  It can be quite dramatic.  This picture is from 2010.
It is the same variety.  The yellow plants on the right definitely look distressed.  If this was a corn field we would jump all over the yellow corn with side dressed nitrogen to bring it out of its funk.  There are some that believe we should be applying nitrogen to soybeans at this stage.  It is not a new idea.  I played with urea on early flowering soybeans in the 80's and came away frustrated mostly because I was the guy trying to sell the urea.  The idea does have merit. It is a standard practice when nodulation failures occur on first year soybeans where there is no native population of nitrogen fixing rhizobia to infect the soybean roots. Commercial nitrogen fixes this problem very efficiently.
However, this is not what caused the yellow beans in the photo.

The field has a history of soybean production.  Nodulation was excellent as shown above.  There is a rotation difference, with wheat being the previous crop on the left and corn on the right.  It looks like the beans on the left would be at least 10% better than the beans on the right.  However, at the end of the day the yield difference was negligible.  The ugly ducklings still produced 55 bushels.
Another type of yellow was also on display last week.  A lot of IP soybeans are grown around here and they had to be resprayed for weed control.  The result was lots of scorched soybeans.
It is predominantly surfactant burn as shown by this next picture.
Again, you would think these beans have taken a big hit.  I personally hate doing this to soybeans, but the price needs to be paid.  The yield loss will be tolerable, if the IP premium is captured .  Maybe we should be putting some nitrogen on these plants to help them recover from the shock.  Just kidding.  Because I am not an IP guy I will let someone else figure that out.
The true challenge of trying to manipulate the soybean plant at this time of year is recovering the dollars spent.  Weed control dollars are always a wise choice. Fungicides?  Yes, 2-3 bushels is the expected response and that more than covers expenses.  Supplemental N?  Not a clear cut answer.  We need 2-3 bushels to pay for the added expense.  My experience trying to boost soybeans with fertilizer in early July has produced more failure than success.  I am still open to suggestions.

Corn tillers are also prevalent this time of year.  Perfectly normal and usually not a reason for concern.
You will rarely see tillers on a poor field of corn.  Corn is a grass, and as such tiller buds are present at the crown.  If moisture and fertility are abundant, sunshine hitting the crown will stimulate the tiller buds to grow. This is why tillers are often more prevalent on the edge of the field beside a mowed laneway.  Lots of sun on the outside rows will encourage more tillers.  They can also be found 30 rows into the field like the plant in the picture above.  Tillers are luxury consumers and do not stress the main plant. If the main plant is stressed the tillers will stop growing.  During grain fill, the main plant will consume the reserves accumulated in the tiller to help the grain fill process.
The presence of tillers can indicate you could have possibly bumped your plant population by another 2-3000 per acre because the plants are telling you they are not stressed at all. Genetics sometimes come into play because a hybrid can be predisposed to producing more tillers than average, but this is rare.  

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