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Test Plot Challenge Teaches How to Wisely Spend Fertilizer Dollars

An agronomist and a sales representative get together to make a fertilizer recommendation…

If that sounds like the start of a joke, well, not quite. But it is a story about a light-hearted competition held last year at Midwest fertilizer maker AgroLiquid that also provided some take-home lessons about fertilizing corn.

The company formed nine teams of two people each: an AgroLiquid field agronomist and a sales representative. Each duo developed a corn fertilizer recommendation for a real test plot on each research farm. 

All nine challenge plots were implemented side-by-side. The beginning soil test was the same, and irrigation was uniform.

The results aren’t scientific because the plots weren’t replicated, and field day crowds at the research farm may have interfered slightly with final yields, company officials emphasize. Still, there are learning points.

It’s about the money. In this competition, the highest yield was not the ultimate goal. Rather, the teams were striving for the best economic returns above fertilizer cost (value of the crop at harvest minus the cost of the fertilizer).

The winning plot belonged to Galynn Beer (AgroLiquid national sales manager) and Dan Peterson (Wisconsin-based agronomist). It yielded 237 bushels per acre, trailing two other teams that exceeded 240 bushels. But the Beer-Peterson plot had an economic return of $575 per acre, a few dollars better than the higher-yielding plots.

Beer says he and Peterson made their fertility plan just like they would for a real farmer, with tight margins in mind. “Farmers should hold us accountable on that,” he says. “The real question is, did you get your money back?” 

Above: Agronomy specialist Jeff Brown’s challenge plot had a high yield in the AgroLiquid yield challenge at 243 bushels per acre. It finished third in economic return. 

The 20% Rule 

Beer says when he considers a corn fertilizer budget, he starts at 20% of the expected gross returns per acre. For instance, if expected yield is 200 bushels and expected price is $3.50 a bushel, that’s $700 gross; 20% of that is $140 an acre for fertilizer.

“If the corn market is low, maybe you shave that back,” says Beer. “If it’s high, maybe it goes up. I think it’s sort of intuitive for farmers; 20% is a good starting point.”

The fertilizer cost for Beer and Peterson’s challenge plot was $144, close to the 20% rule, and at the low end of the other teams.

Following are the fertility steps they took. 

Start with N. Nitrogen is the most important crop nutrient, so start there with your fertilizer budget, Beer says. “Our yield goal was 200 bushels an acre. The field had been soybeans the year before, so we could give some nitrogen credit for that. We ended up at 190 pounds.”

Split the shot. Of that N, Beer’s team put 50 pounds on at planting and side-dressed the remaining 140 pounds at V6. They used Y-drop applicators to put the liquid fertilizer at the base of the growing plants. “In-season nitrogen lets you delay the expense of the final nitrogen for two or three months, right up to the last minute,” Beer says. “You get an assessment of how the crop is doing before you spend the money.” 

Add other nutrients. After deciding on the nitrogen plan, Beer and Peterson spent the rest of their budget on 50 pounds per acre of phosphorus, 30 pounds of potassium, 2 pounds of zinc, 1 pound each of manganese and boron, and ½ pound of copper. “These soils tend to be low in potassium, so we were taking a little risk with just 30 pounds,” says Beer. “Fortunately, we got the yield anyway.”

Consider the little things. “Believe it or not, that ½ pound of copper was the biggest debate that Dan and I had,” laughs Beer. “He wanted it in there, and I wasn’t so sure if it was a good use of our tight budget. In the end, we included it, and it helped our yield.”

It also earned Beer bragging rights in his company. 

AgroLiquid Challenge Plots

Yield Return
Team 1 233 $512
Team 2 214 $507
Team 3 222 $486
Team 4 242 $548
Team 5 204 $474
Team 6 244 $567
Team 7 230 $537
Team 8 237 $575
Team 9 213 $494

Variety First, Technology Second

The way Scott Beck saw it in August 2017, two camps were forming around dicamba-tolerant soybeans in Monsanto’s Roundup Ready Xtend System. “Some will say, ‘I will plant all Xtend (next year) because I am afraid of anything drifting onto my fields,’ ” says the president of Beck’s Hybrids. “Another camp will say, ‘I will plant Liberty (Link soybeans tolerant to glufosinate and glyphosate) because I don’t want any drift or volatilization (from dicamba) going onto my neighbors.’ ”

Yet, farmers shouldn’t let weed-tolerant technologies be their sole basis when selecting soybean varieties.

“We sometimes see yield differences among maturities, where one technology might be strong in earlier maturities, and another technology might be stronger in late maturities,” says Beck, “As a whole, the platforms are comparable. We see parity among yields.”

In 2017, University of Wisconsin (UW) agronomists compared Roundup Ready 2 Yield (RR2Y) varieties that tolerate glyphosate with Roundup Ready 2 Xtend (RR2X) varieties that tolerate glyphosate and dicamba. Overall, the 95 RR2Y varieties edged the 124 RR2X varieties by a statistically significant 2 bushels per acre. 

“This doesn’t mean there weren’t excellent Xtend varieties,” says Shawn Conley, UW Extension agronomist. “Just because the technology is there, it doesn’t mean all new varieties will rise to the top.”

The reason for the lower RR2X yields as a whole? “We had significant white mold in several of our tests,” says Conley. On average, the RR2X varieties had 8% more infected plants than did the RR2Y varieties.  

It’s a reminder not to look just at yield potential and herbicide-tolerant technology. It’s also important to look at tolerance to diseases like white mold, Conley says.

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