Still time to side-dress N on corn if you can get in between rains

Crop Consultant Bob Streit, Boone, IA  515-432-0907

Observations across the Midwest, week of June 21-27

 

 

Midwest wide, the USDA crop ratings tell the story. Overall, the major crops look good. One chink in the story is the serious decline in ratings in KS, MO, and all but one state east of the Mississippi due to too much rain. That will reduce yields faster than dry weather will.

Crop consultant Bob Streit

Corn Observations

Corn has recently added two feet of growth as it moved past the V4 growth stage. Once the plants hit V5, they add as much as three leaf stages per week, representing about 15”. It is possible to walk into these fields and accurately project within a few days of when the first tassels might be poking out of the whorls.

During this time the nutrient demand for the big three minerals — N, P & K — is quite high. Also ranking high are calcium, zinc, and others. Ones that are important to the plants that people don’t often think about are molybdenum, cobalt, boron and quite a few others. The supply, though very small, of those minerals is important to such tasks as ensuring N use efficiency, kernel site formation and facilitating the disease immune response.

Monitoring the levels of each is important to the farmers aiming for top yields and is done thru either tissue or sap testing. More growers are paying attention to this, and Midwest Labs, Ward Labs and now Crop Labs in Ohio are staying very busy from samples sent in by interested growers.

The problems popping up are root problems where the ground is compacted and roots are not able to push thru dense layers where the psi requirements to do so exceed 300 psi.

There are not as many problems with carryover from 2014 applied soybean herbicides. Adequate moisture since July allowed better microbial degradation. Beginning last week, I have been able to find the caramel colored lesions at ground level that have become commonplace in recent seasons.  

The last two weeks have been big ones for sidedressing nitrogen for growers who have access to a high clearance sprayer. A high percentage of the total N uptake occurs between the V8 and VT tassel stages, so the thought is to make the final application during that time frame.

Equipment described as ‘dead on dribblers’ or the ‘Y-drops’ attached to the high clearance bars allow this late application. The main negative is if a windstorm occurs tips the corn over and prevent this planned application.    

Soybean Observations

Just as corn has been growing rapidly, soybeans have been slow to show much growth. Until this week, even the April planted beans had barely reached the V5 stage. Now those fields are that far along and they can finally flower. Those cold weeks where the GDU accumulation was near zero caused them to sit still during that time.

With the warmer weather the growth is occurring and about two new sets of trifoliates are being formed each week. The late planted beans are in the same boat and are behind in development. Both of those two sets of plants have to reach the V5 stage before they can flower. The net effect will be that the number of podded nodes is projected to be lower than normal this fall. Steps to add nodes per field by increasing seeding population or implementing steps to boost branch number are what's needed.

A company called New Leaf Symbiotics in St. Louis is conducting field trials on bacteria capable of colonizing soybean leaves where select microbes produce the hormones to instruct the plants to do different tasks. I was down there last week and spent time with the person responsible for the field trials. It is work on such biologicals that is viewed as the way to increase grain production per acre on a level that is more environmentally friendly and affordable. It is some really interesting stuff. A lady by the name of Dr Gwen Beattie is involved in such work at Iowa State.

There are a few problems appearing in bean fields. There are several causes. First might be adverse reactions to herbicides labeled for soybean that are supposed to be easily metabolized, but that did not happen because of the cool and cloudy conditions did not allow that process to happen.

There are also cases where residual products from last year’s corn may not have dissipated as planned. In those situations a person has to recognize if the CYP450 degradation system is involved in detoxification and the cumulative amount of products applied over multiple seasons if soil or weather conditions contributed to their longevity.

In cases where the plants are struggling, a curative response to consider is to foliar-spray nutrition and minerals to help the plant recover and begin growing. There have been good instances of success if the rules are followed.

 

Insects

There have been few problems with insects so far this season. One rare one that I have seldom seen has shown up in western Iowa. The soybean plants in a field were disappearing and declining in health. Upon inspection there were large numbers of millipedes feeding on the cotyledons and roots.

These small, multi-legged creatures typically live and feast on decaying organic matter at ground level. The small bean plants must have looked like a food source for them.

Something that growers who have planted conventional corn should be alert for is European corn borers. These adults are emerging from the 2014 corn stalks where they overwintered in the pupal stage. The fluttering adults can be seen flying around either during calm nights or in the daytime in grassy margins or ditches when you disturb them. The correct response is to look for shotholed whorls appearing in V8 to V10 corn plants. June 25 is typically the end of the first generation problem.

 Weeds, Weeds

Trying to get the weeds controlled or managed in each field seems to be a major task this season. It typically means the each grower gets to use products that were popular fifteen years ago in different combinations to provide the broadest control possible and hopefully enough residual control to last thru when the crops canopy.

With the only new products being reworks or combinations of older or generic herbicides, growers are waiting for new tools. All this in context where there are limited days where it is calm or dry enough to finish the spraying. Few growers long for the days of covering their bean acres with row crop cultivators again, but select fields and problems may require that operation.

Good luck in completing all of these tasks.