As of press time (early August), the 2000 corn crop looks like it will produce record grain yields. By now, I expect many fields have been harvested. I hope you are experiencing the predicted good yields. These high yields were produced despite a dreary outlook during early crop growth last spring. So why is the 2000 corn crop so good? And what does this mean for future management?

First, let's look at early season growth. Last winter had mild temperatures and dry conditions. This allowed corn to be planted much earlier than normal. In fact, most corn in Missouri was planted by late April. Many farmers violated the general rule of waiting until soil temperatures are 50 degrees Fahrenheit for at least three days prior to corn planting. Instead, many relied on the old saying "plant in the mud and your crop's a dud--plant in the dust and your bins will bust." Early on, this did not look like a good prophecy. With dry soils, many cornfields emerged unevenly and did not grow well during the first 30 to 40 days after emergence. And many insects had survived the mild winter. Usually corn "outgrows" this early season insect attack with yields not being adversely affected. However, because of slow early crop growth conditions, this was not the case in 2000. MFA's agronomy department made more corn insect field evaluation visits in 2000 than in the last six years combined. There was also more rescue insecticide treatments applied to corn in 2000 than any year I can remember. Many of these treatments protected the crop's yield potential.

By mid-May, I, along with many others, was predicting a poor to fair corn crop. The insect pressure, dry weather and predicted drought were the basis for this outlook. Guess what folks? The weather gurus and climatic modelers were wrong again. By late May, we were receiving adequate and timely rainfall. This rainfall occurred through tasseling and was the basis for writing this column. Most early season corn growth problems were cured by Mother Nature's intervention. From mid-May until mid-July, the 2000 corn-growing conditions were nearly perfect.

Agronomically, what does high-yielding corn mean for next year's crops? We had high corn yields in 1996 when I wrote a similar column in Today's Farmer. Nutrient management issues are always a concern when high grain yields are removed from the crop/soil system. Two notable differences between the 1996 and 2000 field seasons are commodity prices today are much lower than in 1996, and we had greater nitrogen carryover and less potential nitrogen loss pressure in 1999/00 compared to 1995/96.

With commodity prices being low, producers cut back on fertilizer inputs. As discussed in last month's column, this caused widespread early season potassium deficiencies. These deficiencies disappeared once timely rainfall allowed plant roots to begin extracting potassium from larger portions of the soil profile.

You need to treat crop fertilization, especially phosphorus and potassium, as a continuum. In years following high-crop nutrient removal, I observe many more phosphorus and potassium crop deficiencies than I do in years following average or poor crop yields. Two hundred bushels of corn grain removes approximately 70 pounds of phosphate and 50 pounds of potassium. Corn residue accounts for an additional 50 pounds of phosphate and 210 pounds of potassium.

Nitrogen management and functionality during the 2000 field season was atypical. First, with a warm, dry, open fall in 1999, many fields received fall-applied nitrogen fertilizer too early (before soil temperatures drop below 50 degrees Fahrenheit). Normally, we would have lost much of this fall-applied nitrogen. This did not happen because of the unusually dry weather conditions that prevented leaching, surface runoff or denitrification losses from occurring. Several soil tests throughout the Midwest verified much of the fall-applied nitrogen had converted to nitrate (susceptible to rainfall-induced nitrogen loss) by early spring. The overall condition of the corn crop this year also shows that we had a low nitrogen loss. I observed no visual nitrogen deficiencies before pollination and still have seen little evidence of crops prematurely exhausting their nitrogen supply. This high-nitrogen availability following dry winter/spring conditions reinforces that we lose more nitrogen from fall-applied and preplant nitrogen in "normal" years than we care to admit.

Contrary to popular belief, nitrogen, which is often thought of as a nonresidual nutrient, has many residual characteristics. Corn residues produced in high-yielding years often have greater-than-normal carbon/nitrogen ratios, thus affecting future nitrogen-supplying capabilities of the crop residue.

In 2000, our corn growers did not apply enough nutrients to compensate for higher-than-expected grain yields. The flexible crop/soil system was able to compensate by tapping its limited, nutrient-supplying resource base. This resource base is not inexhaustible. Therefore, if you produced high corn yields this year, remember to replenish the nutrients that were removed.