Technologies for reducing
corn leaf burn caused by foliar spray of urea-ammonium nitrate (UAN) during the
early growing season are limited.
A field experiment was carried out to evaluate the effects of humic acid on
corn leaf burn caused by foliar spray of undiluted UAN solution on corn canopy
at Jackson, TN in 2018. Thirteen treatments of the mixtures of UAN and humic
acid were evaluated at V6 of corn with different UAN application rates and
different UAN/humic acid ratios. Leaf burn during 1 2, 3, 4, 5, 6, 7, and 14
days after UAN foliar spray significantly differed between with or without
humic acid addition. The addition of humic acid to UAN significantly reduced leaf burn at each UAN application rate
(15, 25, and 35 gal/acre). The reduction of leaf burn was enhanced as
the humic acid/UAN ratio went up from 10% to 30%. Leaf burn due to foliar
application of UAN became severer with higher UAN rates. The linear regression
of leaf burn 14 days after application with humic acid/UAN ratio was highly
significant and negative. However, the linear regression of leaf burn 14 days
after application with the UAN application rate was highly significant and
positive. In conclusion, adding humic acid to foliar-applied UAN is beneficial
for reducing corn leaf burn during the early growing season.
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