Rock and Roll Agonomy

Everything I Know About Plant
Health, I Didn’t Learn at McDonalds

By Jason Hanson
Certified Crop Advisor
jlhanson@agriliance.com

As an agronomist, it’s my job to focus on plant health. My profession compels me to keep on top of things like soybean rust, insects and fertility practices. Personal health habits can be another matter, however. Winter meetings (which can include high-cal meals, snacks, and a hospitality room or two) and on-the -go fast food in the summer, combined with too much time in front of a computer answering questions (i.e. what is this? Should I spray?) can result in diet and exercise habits that would send any alfalfa-sprout nibbling, carrot-juice sipping health nut into hypervention.

So it was time to do something about it, you know, clean up my act a little and eat better, exercise more. And then it dawned on me that a commitment to good personal health can be the same as achieving good plant health – it takes effort, you need to stay on top of it, and sometimes, it requires changes in attitude and the way you do things.

As well, our interpretations of good personal health and good plant health can vary greatly.  For optimum personal health, is 30 minutes of exercise daily enough?  Increase protein and cut carbs or vice versa? Six glasses of water daily and eight hours of shut-eye? For optimum plant health, do you need to invest in a fungicide to prevent or cure a disease? Do you have the soil and management style to sustain good plant health? Spray early in the morning or late at night? NIS or oil adjuvant? One pint of glyphosate or three?

To me, good plant health means sustaining a plant through proper and timely management of fertility, soil moisture, pathogens, weeds and insects to obtain optimum plant potential.

When it comes to crop nutrients, everybody concentrates on nitrogen first and foremost. It is the largest used nutrient for production agriculture and is the largest dollar spent on the fertility program.

But nitrogen actually is not the largest nutrient used by the plant. Actually, that honor goes to carbon, hydrogen and oxygen. Since we can’t really control those nutrients, we focus on the next three: nitrogen, phosphorous and potassium. Nitrogen by far gets the most attention.

The price of nitrogen products is very much a concern as they start to take a bigger piece of the production cost per acre. So the focus starts to center just on nitrogen, leaving the money left over to be cut for phosphate and potash. “So what if I cut P and K,” you say. “If I would have had more nitrogen on my wheat acres last year, I could have bumped my yield or protein or both. Phosphorous and potassium would not have done that for me.”

But just like your body needs balanced nutrition, so do your plants. Just as your body will respond to nutrition deficiency, so will your plants.

The Phosphate and Potash Institute had a recent article that went through how research done with potassium and manganese has an impact on soybean disease occurrence, when fertility is a planned approach to disease prevention. How would most of us ever know if our soils were lacking zinc, copper, sulfur, or calcium if we never soil tested for it? I would guess that most of the soil samples that Agvise Labs receives only request N, P, K, salts, and pH. Sure zinc is requested if the crop is going to be corn, flax, or dry beans. But that is as far as most things are taken.

So you are sitting with a silty loam soil with a pH of 7.8, the salts are low, nitrogen is lower than expected at 22 lbs per acre, the phosphorous test is 6 ppm and the potassium level is 354 ppm. What does this tell you? The pH and salts should make it good to plant soybeans, chlorosis shouldn’t be a problem; and your levels of each nutrient are fairly common. Put on X amount of each nutrient for the yield goal of whatever crop you are going to plant, and away you go. 

But just as you may have a good handle on your health, at regular intervals a more complete and detailed physical is recommended with your doctor. So it is with plant health. The basics of a soil test are recommended at a minimum, but getting a complete test done with all the micros levels, base saturation, cation exchange capacity and organic matter would be good as well, especially when farming new ground.  That way you could have a great base of information to draw from in making management decisions.

Then after the nutrients are applied and the crop emerges, it is time for timely checkups, in the form of plant tissue analysis. Different plants have different uptake needs at different times during the growing season. During what growth stages do dry beans need zinc the most? Or copper for small grains or sulfur for canola? By monitoring your crop at different stages, it’s like a regular checkup with your dietician or doctor.

Sometimes too much of a good thing is not real good either. When phosphorous levels are very high, it can make it tougher for zinc uptake in higher pH soils. There are other interactions with potassium and magnesium also that can throw plant health out of acceptable levels when one gets higher than it should. For instance, corn deficiency from zinc is around 25 ppm from a tissue analysis, but symptoms don’t show up until about 19 ppm . So you can be losing yield even with nutrient deficiency symptoms aren’t present.

Plant health starts with crop nutrients, and involves using tools like the right herbicides, fungicides (both foliar and seed treatment) and insecticides if needed. A plant can better fight off infections, just like you and I, if it is healthy and getting its daily requirement of essential vitamins and minerals.

To sum up: loading up on nitrogen can in some cases be detrimental with certain genetics, so you need balance and constant checkups. A base soil test and follow up tissue analysis is a good start to help keep your crop within its needed nutrient guidelines for a healthy plant.

So you can see that we can apply some of the same principles of health to people and plants. The next time you walk into a fast food establishment and order up, think about your crop acres. For optimum health, keep those nutrients balanced.

Hanson, Devils Lake, N.D., is a regional agronomist with Agriliance.