|Information condensed from D. M.
Sullivan, J. M. Hart, and N. W. Christensen. Nitrogen Uptake and Utilization by
Pacific Northwest Crops. Pacific Northwest Extension Publication, PNW 513, January
1999. Order this
The major factor affecting time of biomass accumulation for peppermint is the
method of rust control (flaming vs. chemical control). Peppermint that is flamed
produces biomass over a shorter growing season than fields where chemical rust control is
used. Fields flamed for rust control begin harvestable biomass accumulation
approximately 30 days later than unflamed fields. Vigorously growing fields where chemical
control is used produce more biomass than fields that are flamed. Peppermint growth
follows a similar pattern when either method of rust control is used, producing between
8,000 and 10,000 lb dry matter/acre.
N Uptake. Peppermint that is flamed
accumulates N at a faster rate than fields where chemical control of rust is practiced.
However, both techniques produce plants at harvest with approximately the same amount of
N, 170 to 250 lb/acre. Flamed and unflamed peppermint have different N uptake rates.
Flamed mint has a maximum N uptake rate of approximately 3 lb/acre/day, while the maximum
N uptake in unflamed mint is about 1.5 lb/acre/day. The peak N uptake period is between
June 15 and July 15.
Management. Nitrogen fertilizer rates of no
more than 200 to 250 lb/acre are necessary for adequately irrigated mint. N can be
supplied through the irrigation water or to the soil early in the growing season. Supply
approximately 175 lb/N/acre before mid-June where peppermint is flamed or by mid-May where
chemical rust control is used. N applied in late July or August is likely to remain in the
soil after harvest.