Renewable Farming

Crop Update: Are micronutrients limiting response to your applied nitrogen?


After stalk N testing was performed this fall there were growers who found out their stalks’ N levels were in the high to very high range — but their yields didn’t seem to correlate to those findings. In other words they sometimes found that sidedressing N did not produce any yield increase.

Jan. 3, 2017  By Bob Streit, crop consultant — Who or what could give a clue as to what had occurred in the field and what is the course of action to follow next season? This is a great chance to play armchair quarterback.

First of all the questioner should find out exactly what form of N or compound was tested for, and how deep cores were pulled from. Did the test look at nitrate N, ammonia or ammonium, or organic matter containing nitrogen? Also, did they test down to 30 inches or just to 6 or 12 inches? The cores taken down to 12 inches may represent only 40% of what was in the soil. Thus a false low reading may have been generated. The precision N specialists recognize this and are mostly testing deeper than 12 inches.

Another factor to consider if supplemental N didn’t seem to pay: It could relate to deficiencies in Zn, Mg, and Bo levels as well as Moly. Shortages in each of the first three and especially the last one can make plants unable to process available N into plant material. In the past year or two, more crops people who are being educated on the role of micronutrients are requesting that tissue testing be done to detect such deficiencies.

Remember that one of the major labs in our region is seeing Moly being deficient about 95% of the time in corn. When we tested soybean leaves in our 2016 tissue testing, it was also commonly deficient. At a cost of about $3 – $4 per acre, correcting the problem is often the cheapest route to follow, especially when buying and sidedressing an additional 40 to 60 lbs. of N would cost a lot more and still would not solve the underlying problem.

Variety Choices

There are still lots of pieces of performance data to sort through in deciding what variety packages to plant in 2017.

In the past three or so seasons, we have seen the fuller season hybrids produce more bushels. Was this a trend, or a function of farmers planting earlier and being able to capitalize on an excess of GDUs accumulation? Will that trend continue or will we see a cooler season arrive? More than one grower has asked what they should do, and if they should plant a higher percentage of their acres just south of Hwy 20 to 110 and 112 RM hybrids rather than choosing ones in the 103 to 105 RM range.

The correct answer is typically not in black and white. Instead, a wise choice applicable to most areas would be to evaluatel drying capacity, expected days required for harvesting all of your acres, past history of stalk diseases and drainage potential in each field in the spring if conditions are wet.

One additional consideration might be residual P levels in each field, because the developmental pace of the plants will be partially controlled by the availability of level of that nutrient. Plants develop faster where P levels are higher.

The latest issue of the INPI (International Plant Nutritional Institute) spent an entire page on phosphorous. They first discussed how P was vital to energy transfer within the plant once the chlorophyll molecule had captured sunlight energy. P was vital to forming ADP which is then transformed to ATP as the excess energy is transferred around within the cells. Besides being vital to energy transfer it is used to make chromosomal material. If and when low P conditions exist the plants will pull P out of the stored P amounts which can limit the ability to pull in additional nutrients limiting growth and eventually yields.

On the glacial till soils in central and north central Iowa and southern Minnesota where the pH levels are often above 7.4 growers may want to take steps to halt the tie up that can occurs on high pH fields. Check to see what products work to stop this chelation or check into in-season foliar applications of P.

 GMOs at Ohio State

In an interesting piece there were comparisons made in plot work with Ohio State U where conventional hybrids were compared to those carrying above and/or below insect traits and herbicide traits in 2014 – 2016. The total bushels produced from each of those groups vary and no data is given as to what insects may have caused problems in those targeted years and if treatment threshold were reached. They also did not place dollar figures to hybrids that would have varied by over $200 per bag. I had not seen the results of the trials until now and they had not been publicized much at a time when growers are making crucial decisions. The data was sorted out in the 2014 thru 2016 Ohio Corn Performance Test.

Beans on Beans

In today’s situation where more bean acres are being forecast for the coming season we may see growers in fringe areas consider planting beans following beans. This is typically not recommended as it is supposed to lower yields. In the Wisconsin Extension newsletter the recommendations are given for those who might be considering the very practice. They suggested choosing varieties rated good on diseases and switching both maturity and varietal families. Since both BSR and SDS could be a soil borne problem the suggestions could be accurate.

What I have seen in recent years where due to rotations or delayed planting, farmers who were forced to plant second year beans and observed the rules of being cognizant about disease and SCN ratings produced yields in the high 70s to low 90s. This should be repeatable in 2017 if the situation demands it. One additional recommendation may be to rotate source of SCN resistance as well.

 Banvel Tolerant Beans

In an issue that has already gotten a few people killed in the Delta Country, and has been an issue in a few Iowa locations, we will have to see how it is played out in Iowa this year. We all know that broadleaf weeds are tougher to control because the incidence of tolerance of actual genetic resistance is greater, and their seeds germinate much later than they used to 20 years ago. The rules of when to apply and not apply are more restrictive than any rules before. Violations and resulting damage is also likely to be more noticeable, and due to today’s economic climate the legal system may come into play quicker. Plus what is also different is that back in the 1996 -97 era there were many parties stating that resistance was not going to be generated and the naysayers to this belief were in the minority. In this case several major companies and university researcher are stating they have already developed resistant strains of weeds in the greenhouse.

In Wisconsin work, yield studies show the new beans are 1.8 bu. per acre less than the RR2Y beans. An added note it that the Texas Wine Growers association stated their opinion as well as how much the wine growing business has expanded in their state and it importance to Texas economies. The same could be said for wine and peach growers in many other areas of the country.

We will know in a few years how this might turn out. Until then follow any recommendations as any label specifies and make use of drift retardants if you find yourself needing to use them.   

Bob Streit  (515) 432-0907