Nutrient Management

Managing the fertility levels of the fields on your farm is an extremely important aspect of growing the most profitable crops possible. One common mistake in this area seems to be that fertilizer application rates are not always keeping up with nutrient removal by the harvested grain. Below is a guide to the amounts of these nutrients that are physically removed from the field when the grain and/or fodder is removed.


Nutrient Removal (lbs/bu grain)





S        Zn

Corn – grain




.07    .001

Corn – Silage (lbs/ton)




.9      .0018

Soybeans – grain




.22    .001

Milo – grain




.14    .0004

Wheat – grain




.6      .003

Wheat – grain and straw
Alfalfa (lbs/ton)




.22    .003
5.4    .1

A common practice for fertilizing a corn/soybean rotation is to apply P and K ahead of the corn crop and have some carryover for the soybean crop. This can be a very good method, providing that the rate of nutrients of the application is sufficient to keep up with the crop removal of both crops. As an example, if you harvest 100 bu/acre corn the first year and 35 bu/acre soybeans the second year, your nutrient removal would be:

P removal       100(.38) + 35(.8)=     66 lbs/acre P

K removal       100(.30) + 35(1.4) = 79 lbs/acre K

S removal       100(.07) + 35(.22) = 14.7 lbs/acre S

If you are fortunate enough to raise even better crops in the two year period, your nutrient removal climbs even higher. At 130 bu/acre corn and 40 bu/acre soybeans, your removal would be:

P removal       130(.38) + 40(.8) =    81.4 lbs/acre P

K removal       130(.30) + 40(1.4) = 95 lbs/acre K

S removal       130(.07) + 40(.22) = 18.2 lbs/acre S

So, if your program is to fertilize every other year, you will want to keep in mind what you expect to take off the field and make sure to apply at least as much as you will remove with the harvested crops. If you aren’t keeping up with this removal, in time, your soil test levels will drop to a point where yields will be substantially reduced. If you have low testing soils, a good practice is to cover the nutrient removal, plus add some extra to build the soil test levels to a point where yields will not be limited by poor nutrient availability.


Starter fertilizers are an excellent way to get your crop off to a good start in the spring, but don’t get caught up in the misleading propaganda that a low rate starter is all you need to grow the same or even more bushels per acre. While it is true that yields can be maintained or improved in the short run by the use of a starter-only program, it is physically impossible to get enough fertilizer on to cover your crops total needs with a few gallons per acre of a starter solution. As an example, 8 gallons of a 9-18-9 starter would supply the crop with approximately 15-16 lbs/acre P and 8 lbs/acre K. Can you guess where the crop gets the rest of what it needs? Yes, it has to mine the rest from the soil. Therefore, over a fairly short period of time, if you aren’t applying other forms of fertilizer to make up the deficit between the amount of nutrients supplied by the starter and what the crops are taking out, the nutrient levels in the soil will be depleted.

With crop prices at an excellent level right now, do you want to cut your yields short by not having an adequate level of fertilizer in the field? Your return on your investment in fertilizer is usually pretty substantial and good crop prices makes it even more beneficial to make sure fertilizer is not your yield limiting factor.