With 90-plus degrees and sometimes 100 degrees and strong winds the potential evapo transpiration rate and the pan evaporation rate have been extremely high these past two weeks.
PAT is a calculated rate of moisture use based on air temps, air humidity and wind speed. It is typically calculated for each crop and adjusted for plant growth stage.
PAN is a measurement of how much moisture would disappear from a metal pan when water is exposed to the weather.
Normally, corn in the V4 to V6 growth stages will be using less than .1 inch per day. This week’s hotter and windier conditions would have increased that rate slightly.
We did see plants on end rows and other areas of compaction that were wilting down during the heat of the day.
In Nebraska or Kansas such conditions would have prompted growers to turn on the irrigation pumps to fill the moisture profile and keep from getting behind if the temps didn’t cool off.
With us having to depend on natural rainfall we don’t have the luxury of turning the pumps on.
It would be nice to have, but the cost of owning, powering and maintaining such systems would shock the average drylander.
The good news is that if any of us had been informed in early May that we were going to have a very nice looking crop by June 1, we would have bet against such a thing happening.
Well the heat turned on over Memorial Day and it has been on since.
Most corn fields looked very good as of last weekend, with even growth and good color.
The soybeans that were up enough to judge looked good, but were several weeks behind schedule.
A number of people suspect that the figures on percent of soybeans planted has been overstated in that there were still a decent number of planters operating this week.
Those fields look good for May 20, but not so good for June 10.
Beginning in the past week more corn fields began to show a few warts.
It may have begun in the second-year corn fields, of which there are now a surprising number. The late spring decline in the corn-to-bean price ratio became highly in favor of planting more corn.
Seed dealers saw more bags of beans being returned as many customers found that the ground worked great and the prospect of capturing $7 per bushel new crop corn was very attractive.
In those fields the stands grew uneven in both color and size.
The problems seem to be related to both residue control and placement of nitrogen.
Good stalk breakdown helped as did having several sources and placements of nitrogen. Time will tell which management response will be the correct one.
Will the plants recover in time if the roots get deeper or does one need to get aggressive and side dress additional nitrogen?
If one studies the leaf color and the striping pattern it becomes apparent that more than a shortage of nitrogen is at play.
Rather than just yellowish leaves and a lighter colored midrib, what is visible is a light green/dark green striping pattern.
This is more indicative of micro-nutrient shortages that need to be tested, and then fertilized for if a deficiency is documented.
Around the globe
When I was down in Brazil and traveling in the two big production states of Mato Grosso and Parana, I was surprised at how much of the after soybeans double cropped winter acres had been planted to corn.
In Parana the figure given by local agronomists was 75 to 95 percent.
The corn as of late March ranged in size from just planted to shoulder high in height. The crop ends up either in domestic markets or exported while that raised in Parana goes into poultry diets.
Current weather reports tell that the fall rains stopped about a month earlier than normal, which was multiplied by the fact that the late-arriving fall rains delayed planting of the first crop.
For comparison purposes, when corn was planted and harvested as a first crop in Parana fields near Londrina it averaged 190 to 195 bushels per acre. Their skills as corn growers are improving.
As bean growers their tougher conditions and insect and disease pressures demand that they manage in a much tighter fashion than we in the U.S.
More tissue testing
More of the major fertilizer retailers have spent time training their agronomy staff on the value of tissue testing and have taken steps to offer the sampling service to their customers.
They should be commended for this and recognized as being forward thinking. What is going on? Aren’t they and growers satisfied with only supplying N, P, and K when the plants are begging for Ca, S, Mn, Mg, Cu, Co, Zn, Ni?
In Brazil and Argentina the fertilizer and crop advising industries recognize that 14 to 15 different elements are needed by the plants to form all of the different plant parts, grains, enzymes, factors, co-factors, phytoalexins and other substances produced by the plant and possibly used to maintain a decent disease defense mechanism.
Most of their fertilizers contain all of those. In addition there are other compounds used in conducting cross talk systems as the plants and their roots work synergistically with microbes on the leaf surfaces and within the rhizosphere to fulfill their roles.
Just because we don’t understand all of these systems doesn’t mean they aren’t important.
If you have been observant the past week you will have noticed more areas within both major crops that have turned a lighter color. The same thing happened last year and in most cases no corrective steps were taken either because very few people noticed it or they didn’t understand what was going on.
Given the fact that we have now seen huge increases in the price of grain, final yields must have been affected and could be again. Now is the time to sample.
It takes only a few minutes to pull whole plants, dry them and send them to the labs that offer testing services. Those retailers offer information booklets that describe the different symptoms of deficiencies and the ramifications of plants running short.
If you visit with the testers and discuss long-term summaries it becomes apparent that low nutrient levels have been with us for a while.
It is also very interesting to find out how many experts rely heavily on not knowing the facts.
Good luck on getting everything done. An old Indian prayer is “May the winds blow gently the next week and timely rains fall.” We will need both.
Bob Streit is an independent crop consultant and columnist for Farm News. He can be reached at (515) 709-0143.
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