Stacy Campbell: How much fertilizer can safely be placed with seed?
All fertilizers are salts and can cause germination problems if too much is placed with the seed. Too much fertilizer may inhibit germination completely, which results in a loss of stand. In other instances, too much fertilizer placed with the seed may simply delay germination, or it may result in weak seedlings with poorly developed root systems. In either case, the affected seedlings will be at a competitive disadvantage and a loss of yield potential may result.
Several points should be kept in mind when evaluating seed-placed fertilizer.
- Soil between the seed and the fertilizer band provides a buffer.
- The potential for injury from seed-applied fertilizer is greater for sandy and/or dry soils.
- Certain types of fertilizers should never be applied with the seed, even at low rates. No urea-containing fertilizer (urea, UAN solution) should be placed in direct seed contact. The hydrolysis of urea to ammonia can result in ammonia toxicity to seedlings.
- Reduce rates 30 percent for grain sorghum. We suggest no seed placed fertilizer for soybeans, sunflowers, or dry beans.
The amount of fertilizer Nitrogen (N) plus Potassium (K2O) applied in direct seed contact should not exceed the values presented in the above table. These guidelines are relatively conservative. Some producers have gotten by with using higher rates at times. However, rates higher than those in this table have real potential for causing germination problems in some years.
If N and Phosphorus (P) are applied without any K2O, such as using 11-52-0 or 10-34-0 then rates can be increased. In corn on 30 inch rows in medium to fine textured soils, the maximum amount of fertilizer that can be safely applied with the seed is 72 lbs./ac of 11-52-0 and 6.9 gal/ac of 10-34-0. In sandy or dry soils 54 lbs./ac of 11-52-0 and 5.2 gal/ac of 10-34-0. In grain sorghum, 30 inch rows in medium to fine textured soils 50 lbs./ac of 11-52-0 and 4.9 gal/ac of 10-34-0. In sandy or dry soils 38 lbs./ac of 11-52-0 and 3.6 gal/ac of 10-34-0. Remember this is assuming no added potassium (K20).
Stacy Campbell is an Agriculture and Natural Resources agent in the Cottonwood District (which includes Barton and Ellis counties) for K-State Research and Extension. You can contact him by e-mail at firstname.lastname@example.org or calling 785-628-9430.