FERTILIZER PLACEMENT: BROADCAST OR BAND
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
There is no difference between broadcast and band application except in amount of fertilizer. Use an ammoniated fertilizer (ammonium sulfate/nitrate/phosphate) and avoid urea if banding. Place band to the side of the seedpiece (2 inches) and slightly below but never above. There is no need to apply more than 200 lb N/acre broadcast.