Corn growers in southern Minnesota have become accustomed
to using high rates of nitrogen fertilizer. Regardle-
ss of their experience, there were still questions about
proper rates for maximum yields and profits. Also, questions
related to nitrate movement out of the rooting zone
and possible effect on ground water were unanswered.
In the 1940's, nitrogen costs were high compared to the
value of corn, thus nitrogen use was unpopular. Knowledge
of nitrogen use was also limited. Ammonium sulfate was a
popular form at first, then ammonium nitrate became the
chief form of nitrogen.
During the early 1950's, anhydrous ammonia was introduced
and its direct application became popular. Along
with this nitrogen form came many new questions.
In the 1960's, nitrogen prices dropped to as low as 3%
cents per pound and rates per acre climbed accordingly. In
the 1970's, shortages occurred and prices rose sharply.
Recommended rates again needed study.
By the late 1960's, concern was increasing over nitrogen's
·downward movement to the underground water This
was· accompanied with a consistent increase in nitrogen
use throughout the state. Table 1 shows that nitrogen
use increased from 1,500 tons in 1945 to the present
figure of over 560,000 tons.
Fenster, W.E.; Overdahl, C.J.; Randall, G.W.; Schoper, R.P..
Effect of Nitrogen Fertilizer on Corn Yield and Soil Nitrates.
Minnesota Agricultural Experiment Station.
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