Studies
on cut Russet Burbank seedpieces in Idaho showed that ammonium
sulfate (120-360 lb N/acre) banded six inches deep and six inches
to the side resulted in more growth cracks and culls than when
broadcasted and worked into the soil 6 to 8 inches. Harvested
tubers from fields in which the starter fertilizer was broadcasted
had a higher percentage of US#1, greater yield of US#1 and more
larger US#1 tubers compared to banded application.
However,
in California, another group reported no difference in yield between
band or broadcast application of ammonium sulfate (60-240 lb N/ac).
In
New York, researchers reported that seedpiece contact with urea
(150-300 lb N/acre) may delay emergence and early growth.
Urea was banded in the furrow. Ammonium nitrate did not
have adverse effects when in contact with the seedpiece. The recommendation
was to use an ammoniated fertilizer with mono ammonia phosphate
(MAP). Placement is best 2 inches to the side and slightly below
seedpiece. With this placement, urea also did not injure
the seedpiece. This recommendation also comes from research in
Maine where no difference between broadcast and band application
was observed with superphosphate.
In
work done in Ohio using ammonium sulfate and sodium nitrate, injury
to cut seedpieces was observed when in contact with the fertilizer.
Whole (single drop) seedpieces were not affected.
The
effect of contact with nitrogen in the soil seems to be related
to water movement from the seedpiece or sprout and not due to
some toxicity. Injury is worst the more soluble the nitrogen
or phosphorous form and the drier the soil.
Injury
symptoms to watch out for:
1.
retardation of sprout growth,
2. inhibition of soil moisture absorption by seedpiece (shriveling
at cut surface),
3. sever injury and possible death of sprouts growing into a fertilizer
band (especially under drought conditions),
4. prevention of wound healing of fresh cut surfaces by contact
with fertilizer.
Injury
symptoms after emergence due to contact:
1. delayed sprout emergence
2. weak, skinny plants
3. poor stand due to seed rot or sprout death
