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CROP WATCH

Are your crops as green as they should be?

June 16, 2017
By BOB STREIT , Farm News

And now into the middle part of June. The landmark date of June 21st is about two weeks away and the Fourth of July is a short four weeks from now. Those dates are important in that the old saying "Knee high by the Fourth of July" used to be a standard that has gone obsolete as we commonly have corn fields tasselling within a week of the Fourth. We tend to gauge how well the corn is growing and if our fields will be safe from frost if the last half of summer holds normal temps and the first major frost falls within its normal week. Now the 21st of June is when the soybean plants begin to flower, assuming they have formed at least five trifoliate leaves. In Iowa the corn crop looks better than it did a week ago, but is way behind where it was in 2016. A high percentage of the soybeans were planted in late May or even early June. The plants just don't seem to be growing at a rate we would consider normal.

I saw what the crops looked like along Hwy 80 and south in Illinois last week and then again this weekend as we attended my sisters surprise birthday party on Saturday in Chicago. We took the I80 route out there and the Hwy 20 route on the way back. Their fields and their crops are still showing the effects of having received six to ten inches of rain in one frontal boundary that moved through in early May. There were many corn fields where the plants were only in the V3 growth stage or even shorter. Many fields of soybeans had been planted or had emerged in the last seven to ten days. Their chances of beginning to flower by June 21st now appear to be slim to none.

In weather related matter the talk of drought is beginning to be heard. So far the northern plains are having the worst problems with dry soils. After states such as North Dakota picked up almost 100 inches of snow that ended up melting and either running off or soaking into the profile, it turned dry in March and rainfall has been almost nil since then. Apparently quite a bit of the winter and spring wheat has been hit hard and much of it is being baled now. Because much of South Dakota and North Dakota are now home to many corn and soybean acres, getting measurable rains in the next week or two is considered crucial if those small plants are going to be productive.

Late planted corn management

We entered the spring with lots of corn in inventory and a new crop that went in later than normal due to wet conditions and cold soils. Every marketing guru projected only slim chances that we would see any hope of higher grain prices. Now in just one month we have an acreage size that is still unknown with a high percentage of them considered at risk due to poor stands, lost N likely, and much delayed planting dates.

It is too early to lose a corn crop to drought. But it is also known that late planted corn and the stuff planted during muddy conditions and having shallow root systems will have more problems. The crop rating for the ten state area are still very low, especially east of the Mississippi, and south through Missouri and Kansas.

The yellowing of the plants still continues in most fields with some improvement in the appearance and color. We can conclude that cold and saturated soils lacked much biological activity plus many roots had not explored much of the soil profile for nutrients. Last week and this will be the optimum time to pull plant samples and have them analyzed for micro-nutrients. Based on the results from a small batch of samples I sent in last week the exact minerals we suspected to be the cause of some of the yellowing did show up as being deficient. Realize that taking corrective action will have a cost of $6 to $10 per acre, depending on what minerals are short. Not taking corrective action will also have a cost from lower yields, possibly more stalk problems and a greater need for fungicide applications. And even if a fungicide knocks out the causal fungus or fungi, you still have not cured the underlying nutrient deficiency.

If the results from any tissue samples you submitted are classified as being deficient you can either get on the ball and make an application as called for using a shotgun approach or wait another week or two and see if the plants return to a green color. If you have been using a Spad meter, which rates each plant as to its degree of greenness, getting a reading below 60 indicates the plants need help. Make note about whether the yellow plants are just a lighter shade of green or if they are more of a bronze green. If they are the latter the problem could be caused by low N efficiency caused by a lack of Mg, Zn and Cu. Be sure to request that Moly be tested for since is it crucial to good plant usage of N. It is typically deficient about 90 percent of the time. Another trick to speed plant growth up is to start a foliar fertilizer program that utilizes different forms of liquid solutions low in salt and containing P. Charged P carries energy around in the plant as well as building chromosomal material. And different forms of liquid z

If the plants are just in the V3 growth stage now they will have to hurry to get as much grain fill completed before the early plant death syndrome occurs in the Aug 15th to 25th time frame. Try to have the greenest corn in your neighborhood as it is an indicator of healthy corn. Remember that higher levels of Ca in the soil are beneficial as that mineral helps to build strong cell walls and structural rigidity. Also be scouting on a regular basis for early signs of leaf diseases. Before religiously applying fungicides get a plant mineral analysis done to see if a nutrient shortage went unnoticed and was the cause of the plants not be optimally healthy.

Do your own math now. Count the number of leaf collars that plants in your different fields now have. Then assume an average of 2.25 leaves forming per week to grow the 18 to 19, which is a normal count. Recognize that no dry matter gets deposited until late blister stage, which is about ten days after pollination. From late blister the grain fill period should last about another 50 days for hybrids in central Iowa. Based on your calculations when should your grain fill period get over with? If your date is after August 20th or 25th, what do you plan to do to keep your plants healthy enough to survive as long as they need to? Wishing that it happens rather than being proactive and making it happen using the correct plant health products could be doubly important.

Soybean management

In a high percent of the bean fields that plants look like they will be severely challenged to meet pre-seasonal expectations. The stands are generally lighter and much later than in 2016. Again there are aggressive growers who will be helping their bean plants by applying the fertilizers and nutrients known to improve plant health while also working to add additional branches. There are several products that have been used successfully. These often center on sugar, liquid forms of high grade P, and hormonal products.

What I have seen is that guys who formerly planted beans late (mid June) after taking off an alfalfa cutting or a cover crop and normally saw yields in the mid 20s, changed course and learned how to maximize their plants physiology and architecture. They learned that yields in the mid 50 Bu range planted after June 10th were possible.

In the meanwhile keep a sharp eye out for plants that are not as green as they should be. There is still time to take corrective action as soon as problems are identified.

Bob Streit is an independent crop consultant and columnist for Farm News. He can be reached at (515) 709-0143 or www.CentralIowaAg.com.

 
 

 

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