Agronomy Talk

Agronomy Update

How to "Know Your Numbers" - Fertility

Published on Friday, February 6, 2015

In continuation of our short series on “Know Your Numbers,” let’s explore some ways to manage fertility to improve profit and then we will look at some easy practical ways to farm more profitably.

Why fertility? When we looked at our cost per acre last week we saw that fertilizer is one of the biggest variable input costs for corn and beans. This means it holds potential to have a big impact on yield and profitability.

There are three "Know Your Numbers" for fertility.
• Soil sample every two to four years
• Know the critical levels
• Know your removal rate

Think of your soil as a bank account. Your soil holds fertilizer for the crop and you make debits when you harvest your crop and credits to the account when you apply nutrients.

Continuing this analogy of a bank account, your soil test is like that bank statement you get in the mail. It assures you of how much you have in the account.

Critical level is like knowing your minimum account balance the bank requires. Universities have tested how different fertility levels affect yield. Then they developed critical values that assure you that P and K won’t be limiting factors when your soil tests above these values. (Click here for critical level chart for P and K).



For your checking account though we have to keep a ledger for day-to-day transactions. Looking at the debits and credits of your ledger gives you an idea if your account value will increase or decrease over time. That is why we need to know our removal rate. Removal rate will tell us if we are putting on enough fertilizer to replace what we remove each year. (Click here for a removal rate calculation)



First of all, pH. Optimum pH for corn and soybeans is 6.5 to 7.0. If your pH is out of whack, it is important that we get that fixed before focusing on P and K.

When you know these three fertility numbers you can best spend that fertility dollar where it is most needed and save where it won’t hurt you!

Easy Practical Ways to Farm More Profitably
Nitrogen: Each year we spend around $125+/- for Nitrogen (N) on each acre of corn. Here are some ways we can best manage N investment. Put N on later and split apply N. Beck’s PFR multi-location, multi-year data shows us that practices to put N on later AND split apply give us a LARGE return per acre for the same dollar spent on N! 10 gal 2x2 with the planter and the rest side-dressed at V3 gave us over $45 per acre more than preplant N!



The second important N management decision is RATE. The right rate varies with yield potential, soil type, previous crop, and N price. In Beck's PFR program we’ve found that most of the time the optimum N rate following soybeans is around 180 lbs.

Soybean planting depth: When I ask most groups “how deep should we plant soybeans?” many tell me 1.0” to1.5”. And that is what they taught me in college, so it makes sense. If you agree, do an easy test on your farm this year and plant some of your beans at 1.75”. Let me know what you find. Split the planter and do a side-by-side comparison.

Why should you read a 2,4-d label?


Why should you read a Valor® XLT label.


And compare the two visually:

                                                   1.25” Planting Depth


                                                    1.75” Planting Depth

More uniform moisture, more uniform emergence, better nodulation early.

Plant early: 2-6 Bu./A. advantage on Beans, 6 to10 Bu./A. advantage on corn and dryer corn.

Don’t plant too fast!



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Alex Johnson

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