Over the past fall, winter, and spring, I have received many calls and e-mails from individuals asking about fertilization practices to improve efficiency. High fertilizer prices will make it harder for producers to be profitable, and the same is probably true for input suppliers.

Whether it’s producers considering knife application of P and K, or corporations working on N-efficient germplasm, efficient fertilizer use is a good thing. However, producers and corporations alike seem to hope that increasing fertilizer efficiency will allow dramatic reductions in fertilizer rates. Unfortunately, this is not the case. No matter how fertilizer is applied, and no matter how it’s taken up by crops, it’s impossible for efficiency to go above 100 percent. And if a low rate is 100 percent efficient, but is less than what is removed in the harvested crop, the system is being mined. That can only go on for so long.

In some cases, mining nutrients from the soil is appropriate. In soils that are very N-rich, it can be a use-it-orlose- it situation. With P and K, loss is rarely an issue, but it can be a good business and agronomic decision to mine soils with high native soil test levels for a period of years. Some of our river-bottom fields would fall into this category. But in the long run, every field must eventually come to the point where nutrients applied, as fertilizer or otherwise, are at least as great as nutrients removed.

It is worthwhile knowing typical nutrient contents for your crops and thinking about how many pounds of N-P₂O₅-K₂O are being removed when you harvest. Values for some of our most important crops are shown in this table:

Crop	Unit	N	Amounts removed: P2O5	KO
Corn	lb/bu	0.8	0.45	0.35
Soybean	lb/bu	4	0.8	1.4
Wheat	lb/bu	1.4	0.6	0.3
Fescue Hay	lb/ton	40	12	35
Alfalfa Hay	lb/ton	45	15	45
Fescue pasture	Cow/calf pair	10	7	1

Peter Scharf
573-882-0777