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CROP WATCH

August 10, 2018
By BOB STREIT - Columnist , Farm News

So far this growing season has been one for extremes, nothing has been average. April was the coldest and snowiest on record in many areas, as in northern Iowa and southern Minnesota.

The conditions caused a delayed planting season in most areas with the crops being planted weeks or months late. Most parts in the Cornbelt had not experienced prevented planting for a few years, but did this spring. Most of us assumed the corn crop was going to be late in tasselling and maturity. We were wrong, as May was the warmest on record and the corn grew quickly as it accumulated 25 to 30 GDUs per day once planted. June ended up being one of the wettest on record as parts of the two areas caught as much as thirty inches of rain. Contrast that with July as it was one of the driest on record and now many areas are in need of measurable rain to keep the crop growing. Parts of Missour, Kansas, and points west are in this group with spots receiving as little as 3 inches since planting. As we begin a new month we have to guess what nature has in store for us. It is bound to be a surprise. As to there being a record corn or bean crops, there are good areas but there are also many areas where the operators are ready to close the door on the 20018 season, but their bankers will not let them.

The corn and bean crop development

Last week's 90 F temps pushed the corn crop faster through the grain fill period than is best for depth of grain fill. In 2017 there were no hot days and nights in August to stress the crops. Everyone who understands crops recognizes and knows that driving past a field on a country blacktop at normal speed and seeing the plants 75 to 90 percent brown or bleached white by early August does not suggest plants that will maximize yield. This is not every field, but a substantial percent in the western half and northern one third of the state and enough to affect overall corn yields.

One causal factor had to be the heavy June rainfall that caused shallower than normal rooting and created a situation where nitrogen was lost. Inability of the drainage systems to move water off the fields and restore an aerobic root zone created an oxygen depleted environment that could have led to major N loss thru volatilization, leaching, or run off. If most operators had a chance for a do-over they would likely have either used an N stabilizer of some sort, or one what was more effective in keeping the N in the ammonia or organic form. In farming there are no do-overs, but we can learn for next year's crop. Be sure to ask what the method of each stabilizers' actions is, and what it does for soil health.

I mentioned last week about my findings with a Minolta Spad meter in different fields. Any reading with this higher dollar instrument which are on a 1 to 80 scale (with 1 being the least green), being below 50 before full dent will lead to reduced yields. The fields that died last week were those with readings in the low 40s or high 30s. They were out of energy. I have heard from a few growers who spent the $249 on the At Leaf instruments are happy with how those instruments work.

The soybeans are highly variable in their appearance and status below the crop canopy. Much of the yield potential that exists in fields across the Midwest will only be captured if timely rains arrive. It's not unusual to see plants with 15 to 17 or more podded nodes, but with 50 viable flowers or small pods that could be saved and filled if several inches of rain fall and sufficient heat and sunshine occur. The chance of high yield marks in many fields being set is not as great as in the last few years.

Disease and insects

There seems to be a wide variance in the disease condition found in most fields. The drier July dried the environment out considerably and lessened the fungal disease threat in corn, especially ones where the mineral levels were in the optimum categories.

There are areas in the Midwest where leaf diseases were bad enough so more acres should have been applied while there were fields that were clean enough that any fungicide application was made because it had been prepaid early by the operator. There is enough variance between varieties, mineral status of the plants in the field, topography, rainfall patterns and hours of dew that each field may get its own rating. After scouting and inspecting a few fields a general trend usually emerges.

A scouting record should include the percent of plants affected by a fungal pathogen (incidence) and then the severity of the infection on most plants. This would categorize the percent of tissue affected or that has turned brown. Together these numbers, with the knowledge how the pathogen acts, and estimate of leaves above or below the ear leaf that have been infected let a scout or farmer make the decision. There are times when things are borderline and you have to imagine the amount of expected yield loss if you do nothing, as well as the cost of each treatment and the percent chance the applications will be effective.

I was in a few fields last week where corn aphids are becoming more numerous on the stalks and leaves. These can be difficult to evaluate as not much information or data has been compiled due to their erratic appearance. Every sucking insect removes sap destined to help the plant fill the seed or grain. What we have seen is that if conditions are dry and the plants are under stress, field treatments of certain varieties back in the 80s in western Iowa often showed a 30 Bu/A return.

A second multi-legged pest seen in corn has been spider mites. Their populations can explode during droughts since a natural predator is a fungus that dies out during dry weather. They also go through more life cycles during hot weather. While most Iowa farmers believe spider mites are a soybean problem, they can actually harm and kill corn in Kansas and parts of Nebraska. Scouting for them is not fun as they leave the field with you.

While soybean aphid populations have remain low, be aware that those numbers are increasing and hitting TTs up near Brookings, SD. Many fields may be mature by the time the higher numbers occur here that no treatment may be required.

Greensnap

I had the chance to team up with Redox Chemical agronomists to visit fields near Avoca in southwest Iowa to walk those that suffered greensnap during June and July windstorms. Estimating yield loss is difficult because the damage os often spotty and irregular. We found fields that had spots where there were no intact plants for 75 feet of row and 12 rows wide. While the percent broken would have been 95 plus the whole field estimate would have been 75 to 80 percent. Right next to them we rated fields that received a silica application and they were under 5 to 10 percent. Maturity, planting date, and other variables were examined and nothing supporting other causes stood out.

We also looked at field plots down in southeast Iowa where moisture has been very short and the plants were under severe stress. There was a very noticeable difference in ear size and kernel count between treated and non- silica treated.

In another field scouting trip to northern Missouri early last week I had the chance to view a biological product meant to make the corn plants tolerant of extreme heat and drought. This was in an area with about 3 inches of rain since planting. The plant appearance and ear size were noticeably improved.

Aug 20th field day

In last week's column I mentioned a field day 4 miles west of Guthrie Center scheduled for Aug 20th, from 9:30 until 3:30 or so. It is a week before the farm progress show, so as not to conflict with that event, and before any commercial harvest takes place.

We traveled down there on Saturday to do more filming of the plots and the corn in them. Now I have seen some excellent fields of corn, including those managed by Kip Cullers and Mr. Childs, but you have to see these and hear how they have been managed. We don't know yet what they will yield, but they are the prettiest, darkest green plants, with the most multiple ears I have ever seen. Some of the products that have been applied are new and you may not have heard of them, but as of 2018 they are commercially available. Our goal was to identify products that worked well together, offer very high ROIs, work to build soil health, maximize fertilizer efficiency, and work within the regenerative guidelines. We often see that it is smaller companies that are willing to think out of the box and develop forward thinking solutions, but don't have the money or influence to get accepted to prove themselves in university trials.

We have bios of most of the speakers and are listing them on our website. The list includes several noted scientists who will be making their first trip into the core of the Midwest. They are looking forward to speaking and visiting with people in attendance and seeing how their products are performing.

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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