ISSUE 1 May 2, 2002
FERTILIZER WITH THE SEED- THE NUMBER ONE QUESTION GOING TO THE FIELD
How much fertilizer can I put with the seed and not have a problem? Fertilizer placement with or near the seed at planting is a very convenient way to apply phosphorus fertilizer for many crops. The practice require no special seeding attachments in most cases, or if it does they are generally less expensive, easier to install, and will work over more acres than fertilizer placement shoes that allow seed and fertilizer separation. However, rates of fertilizer are restricted due to salt and nitrogen content.
Rates of fertilizer that can be applied with minimal risk to small grain seed germination and early spring growth are listed for a variety of soil, moisture and seeder spacing arrangements in a publication-
"Fertilizer Application with Small Grain Seed at Planting", by Dr. E.J. Deibert (NDSU Dept. of Soil Science) NDSU Extension bulletin EB-62.
It can be accessed through a local county agent, or via the internet at the following address:
Look up the bulletin, and then download the PDF file. The other file’s tables are not organized correctly, but the PDF file is.
Tables are also available in the canola fertility circular. For corn and sunflower in 30 inch rows, up to 10 lb N + K2O may be applied (no urea N). But I feel most comfortable with rates slightly more than half of that value. There is no advantage of highest rates over more conservative rates of seed-placed fertilizer in terms of yield for most crops. The rate for solid-seeded sunflowers is proportionally higher than for wide rows, but again, caution is advised.
There is no fertilizer recommended with the seed in row crop dry beans and soybeans. However, some fertilizer may be applied for soybeans in rows narrower than 15 inches. For 6 inch spacing, up to 10 lb N (no urea N) may be applied to soybeans, again, more conservative is better than the limit. Soybean seed placement is sometimes preferred over a broadcast application to save an application charge if soil test levels are low or very low in phosphorus.
For sugarbeet, 3 gallon of 10-34-0 with the seed has become a common practice for many growers. The practice of starter P only for sugarbeets may look good in the short run. However, for many growers sugarbeets was the only crop in the rotation which supported higher rates of broadcast P, enabling maintenance or buildup of soil P levels. Now with a low rate of starter P, where will the maintaining level of P come from? It needs to come into the picture somewhere, or soil test P levels will decrease, quietly stealing yield from all the crops in the rotation, including sugar beets.
A couple of broadleaf crops have a reputation for low response to P. Field peas and flax are especially notorious in studies for not responding to P fertilization. Some studies in flax actually show decreased yields with P fertilization. A couple Canadian provinces have actually taken P off the list of nutrients to apply to flax. Recent studies in Canada have shown that myccorhiza (symbiotic fungi that enable certain plants to take up nutrients more efficiently) are inhibited by P applications to flax, so even though P is added, the net effect is to decrease P uptake.
If these suggestions appear a little confusing, that is why the questions about seed placement will continue despite the information about rates and crops. For complete flexibility, some method of seed and fertilizer separation is needed. There is no truly safe rate of fertilizer that can be applied with seed. However, by observing the restrictions, the risk can be minimized so that yield increases are possible.
NDSU Extension Soils Specialist