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/ grainews.ca
OCTOBER 7, 2013
Features Crop nutrition
Seed-placed fertilizer safety How much seed-placed fertilizer is safe? Pat Beaujot says any seed-placed fertilizer is risky business By Pat Beaujot
T
he cold, late spring this year brought many farmer questions regarding seed-placed fertilizer and how much starter fertilizer including phosphate (P) could be safely seed-placed. My answer is that with today’s seeding equipment and optimally placed sideband fertilizer, any amount of seed-placed fertilizer is too much! Why risk fertilizer toxicity and jeopardize germination and emergence when you don’t have to? I think the right question to ask is whether we need to risk seedling germination with seedplaced starter fertilizer at all, or can we put all the starter fertilizer in the side band close to the seed and still get the “pop-up effect.” Putting all the fertilizer in the side band simplifies seeding logistics, speeds seeding and can eliminate the risk of seedling toxicity.
Is safe really safe? In canola, the seed-placed challenge is especially difficult as it uses high rates of P but can only tolerate low levels of seed-
placed fertilizer. A 35-bushel per acre canola crop takes up 46 to 57 pounds of phosphate (P205) per acre. However, safe-rate guidelines published by Saskatchewan Agriculture caution that only 25 pounds actual P205 per acre (divide by 0.51 to get pounds of 12-51-0 per acre) can be safely applied in the seed row with a knife opener with a one-inch spread on nine-inch row-spacing. These recommendations are for good to excellent soil moisture and do not include other fertilizers like potassium or sulfur. In order to get the crop out of the ground fast with starter phosphorus and still satisfy the crop’s nutritional requirements, the choice is to either cut back on phosphorus fertilizer to meet safe seedplaced guidelines, which will have negative implications on long term fertility, or put some or all of the starter fertilizer in a sideband. From the research I have seen, and what I have seen in the field, I believe that all of the starter fertilizer can be put in a sideband if the sideband is optimally positioned. First, you need to look at
photo: chris bettschen
Differences in canola growth due to topography and seed-placed starter fertilizer. (Far left — mid-slope. Middle — knolls. Far right — flat ground.) the risk of seed-placed phosphorus on canola germination and emergence. In the Canola Council of Canada’s Growers Manual, research from Agriculture and Agri-Food Canada at Beaverlodge, Alta. showed that even small rates
of 10 to 20 pounds of P205 reduced days to emergence and per acent emergence. Just 10 pounds of seed-placed P205per acre increased days to emergence by five days, and 20 pounds increased days to emergence by 10 days. In moist soils, germina-
tion percentage dropped from 100 per cent with no seed-placed fertilizer to slightly over 80 per cent with 10 pounds and to 60 per cent with 20 pounds P205. But with dry soils, germination dropped to 40 per cent at the 20-pound P205 rate.
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C-66-09/13-BCS13097-E
B:22.5” T:22”
S:21.6”