By Brian Hefty

Soil test, soil test, soil test! 

Perhaps the number one issue when it comes to making a fertilizer recommendation for your farm this year is field variability.  Early season flooding with drought the rest of the year created vast differences in yield in the same field.  On our own farm we will have areas of zero and areas of 225 bushel corn… in the same field!  How do you fertilize for that going into next year??

When it comes to phosphorus and potassium, which are pretty non-mobile in soil, it doesn’t hurt anything (other than your pocketbook short-term) if you want to apply a high rate across the whole field, as long as you push that P & K deep in the soil.  In other words, if you broadcast P & K and you already have lots of P & K in areas of fields, you could have an overabundance in the top inch of soil.  If your field suffers any erosion due to rain or wind, those nutrients end up somewhere else, meaning you lose money and you may be contaminating someone’s water.  Either till the soil or deep band your fertilizer to avoid this.

What many farmers are doing instead of this is applying their fertilizer in a variable rate application.  The basis for this is having good soil tests done, either zone or grid-sampled.  Because of this year’s early harvest, you should have more time than normal to do some of this job yourself.  Pulling soil samples is pretty simple and easy.  It’s certainly something you could assign to your son or daughter, too.  We pull our own samples on the farm, which saves a lot of money and ensures the process is done correctly.  With new systems out there, like FarmLogic’s, there is not a lot of thinking you have to do – just drive to the spots the program tells you to, pull samples, and send them in.

DROUGHT TOLERANCE

One of the most important questions that has come up this summer is, “How can I drought-proof my crop?”  Unfortunately, you can never fully drought-proof anything, but you can certainly help your crop become more tolerant to dry weather.  Here is the most important thing I can tell you when it comes to fertilizing your land…

Make sure you have balanced fertility and adequate fertility all season long.

Did you know that if your crop is short on just one nutrient, it will pull more water in, hoping to get some of the nutrient it needs?  In other words, even if your crop doesn’t need water, it will bring more water in.  That’s just water-wasting, which is a terrible thing in a dry year.  Make sure you fertilize with ALL needed nutrients, including boron, copper, zinc, manganese, iron, and sulfur, besides just N, P, and K.

FALL vs. SPRING APPLICATION

This is the big question I get each fall.  Here are my thoughts:

  1. You absolutely have to know your soils.  What is your cation exchange capacity (CEC)?  If you know your CEC, multiply 10 times that number.  That will tell you roughly how much N your soil can hold at any one time.  Don’t ever exceed that number.  If you do, you could lose your fertility and contaminate the groundwater.
  2. I love applying fertilizer in the fall so we can plant early in the spring, but there is no way I want to apply fertilizer where I could lose it.  For us, that means avoiding river bottom fields.  Also, I don’t want to overapply leachable nutrients like nitrogen, sulfur, and boron, especially in the fall.
  3. I love strip-till in the fall.  By tilling that little strip every 30 inches, our soil in the zone is a lot warmer each spring, meaning we get better and faster emergence.  Also, when we want to start planting in the spring, the soil at 10 inches deep is usually too wet to strip-till.  By strip-tilling in the fall we can plant earlier in the spring and our fertility work is done.  Just as importantly, by placing a lot of nutrients down at 10 inches deep, when our topsoil starts to dry out our crops still have water and nutrients a little deeper in the ground.
  4. If you want to do tillage after fertilizing, which is what I recommend in most cases, you need to fertilize in the fall before any fall tillage you have planned.
  5. Even when we fertilize in the fall, we still apply fertilizer on every acre in the spring.  We use starter (pop-up) fertilizer on every corn and soybean acre we plant.  We also put some of our nitrogen on in the spring in every corn and wheat field.  My point is just that fall fertilization is good, but in moderation only.
  6. Use modern technology.  Use a nitrogen stabilizer.  Use a phosphorus product like Avail.  These types of products can help keep your expensive fertilizer in the field and available for next year’s crop.  This is especially important if you are fertilizing in the fall.
  7. Fertilize for the crop you want to raise next year, whether you do it in the fall or the spring.  If you don’t know how many nutrients a crop removes, download our free iPhone/iPad app called Ag PhD Fertilizer Removal.  There you can pull up your crop and your yield goal.  For example, when I select Corn and 250 bushel yields it tells me the amount of nutrients required to produce the grain and the amount required to produce the stover.  In total, did you know that 250 bushel corn removes 141 pounds of actual phosphate, 256 pounds of K2O potassium, 41 pounds of sulfur, and almost 5 pounds of various micronutrients?  Here’s my point.  I still contend that the biggest limiting factor on most farms isn’t just lack of fertility, it’s lack of the right fertility.