Is Returning to "Normal" Good Enough?

• Article

by Kim Polizotto, Ph.D, Director of Agronomy, PotashCorp/PCS Sales

For the past year and a half, we in the fertilizer industry have been talking with farmers, making the case that cutting back on fertilizer applications was not a good thing to do. Economics won out over agronomics, however, and fertilizer use was indeed reduced significantly. With improved economics, fertilizer use looks to be returning to near normal rates for the 2010 crop year, but I think the question we now need to ask ourselves “Is returning to normal good enough?”

On the winter meeting circuit, we’ve all heard at least one seed company say that its goal is to double the yield of corn, soybeans, cotton and canola by the year 2030, compared to a base year of 2000. For most, that means a yield goal of about 300 bushels of corn and 100 bushels of soybeans per acre. These advances are to come about largely from advanced breeding and biotechnology, according to the seed companies. They mention improvements in agronomic practices such as precision agriculture, conservation tillage, seed treatments and planting patterns, but they seem to discount the role that plant nutrition and fertilizers will play in reaching their goals.

The following table shows the nutrient uptake requirements of corn and soybeans at various yield levels. It is obvious that as yields increase, nutrient uptake requirements also increase significantly.

If corn and soybean yield potentials double in the next 20 years, it is clear that higher nutrient levels will be needed. The big question is how our fertilizer programs may need to change and/or adjust to meet these higher requirements. Unfortunately, right now we don’t have all of the answers to this question.

In addition to re-evaluating crop needs at higher yield levels, we need to remember that nutrient removal with grain harvest will increase greatly. The next table shows nutrient removal at harvest at different yield levels. At higher yield levels, just to maintain soil fertility, more fertilizer will be needed to replace nutrients removed at harvest.

Whether or not we believe we will indeed be able to double yields in the next 20 years, industry analysts project that yields will continue to increase. Even if the seed companies successfully develop hybrids and varieties that are more efficient in water and nutrient use, it is probably unrealistic to think our present fertility programs will be adequate.

In order to take advantage of the increased yield potential of new genetics and improved agronomic practices, we need to re-evaluate where we want to be with our soil nutrient levels and how our fertilizer programs are meeting these needs. In my opinion, returning to our traditional fertilizer programs will not be good enough. Our fertility programs will need to reflect where we want our yields to be in the coming years, not where we are today.

The intent of a good fertilizer program is to make sure that plant nutrients are not limiting crop yield. An economical way to test whether plant nutrients are limiting yield is to apply one and a half to two times your normal fertilizer rate in a strip across one of your better fields, and check yields with your combine monitor. If yield potential is low due to weather or pests, you may not learn whether nutrients are limiting, but if yields are high, you can get a pretty good idea if the extra nutrients were needed. It may take a few years of using this approach to get a good idea of your fertility needs for higher yields, but it is a very cost-effective way to get some data for your farm.

Again, if we are going to take advantage of higher yield potential in crops, we need to figure out how we’re going to meet the nutrient needs of the crop. Now is the time to start thinking about where you want to be in the next 20 years and how you are going to get there.