Much of Manitoba’s corn receives liquid phosphorus as a starter in the seedrow. But we cannot apply sufficient amounts with the seed to meet full crop removal (about 44 lb P2O5/ac for a 100 bu/ac crop). The safe amount of seed placed fertilizer depends upon soil type, moisture, row spacing and seed furrow opening. Ontario guidelines base the safe rates of fertilizer on N and K content of the starter fertilizer. For 30 inch rows no more than 10 lb N/ac should be seedplaced – enough to provide 34 lb P2O5/ac of 10-34-0 liquid fertilizer or 8.5 US gal per acre. But based on South Dakota studies such rates could cause stand thinning of 4-9% depending on soil moisture and texture. Most farmers will not be pushing starter rates this high as they should have the bulk of their P needs met through a safer placement strategy.
More on these safe rates of fertilizer is posted on Manitoba Agriculture’s website at: http://www.gov.mb.ca/agriculture/crops/soil-fertility/print,safe-rates-of-seed-placed-phosphorus-for-manitoba–narrow-row-and-row-crops.html
Submitted by: John Heard, Crop Nutrition Specialist, Manitoba Agriculture