In the past, banded fertilizer was usually considered a “starter,” where fertilizer was placed 2 in. to the side and 2 in. below the seed at planting. Times have changed. Use of a banded fertilizer is still important, but the placement of the band can be positioned at several locations. The term “starter fertilizer” is disappearing from the fertilizer vocabulary.
Fertilizer use guidelines from the past have suggested that rates of phosphate and/or potash needed for optimum production can be halved, compared to broadcast applications, if those nutrients are applied in a band near the seed and soil test values are in the low and very low ranges. For corn, the rates are adjusted for soil test levels of both phosphorus (P) and potassium (K).
Broadcast applications of phosphate and/or potash aren't suggested when soil test values are in the very high range. Relatively low rates of these fertilizer materials are suggested if applied in a band (row application). Although this placement may not guarantee higher yields when soil test values are high, this practice may reduce the risk of having reduced yields in some years.
When banded fertilizer is placed near the seed, the early increase in corn growth is primarily the result of the combination of nitrogen (N) and phosphate. For non-sandy soils and conventional tillage systems, the potash and other nutrients such as zinc (Zn) might not be that important if soil test values for K and Zn are in the very high range. For sandy soils, sulfur (S) should be added to the banded fertilizer.
THERE IS A LIMIT to the amount of fertilizer that can be applied close to the seed at planting. Phosphate hasn't been shown to have a negative effect on germination. There are concerns, however, about rates of N, potash and S (if 12-0-0-26 is used).
In general, as the rates of suggested potash increase, the distance between seed and fertilizer should increase. So, if high rates of potash are suggested, plan to place the fertilizer so there is at least 1 in. of soil between seed and fertilizer. The use of 10-34-0 is a good choice for placement close to the seed when soil test values for K are 160 ppm or higher in conventional tillage systems.
There are specific production situations where banded application of fertilizer is especially important for corn production. Using a banded fertilizer has a positive impact on production for the corn, where early corn growth is often hampered by lower soil temperatures associated with higher amounts of crop residue.
Banded application of fertilizer at planting is a key management practice for achieving the best yields in ridge-till, strip-till and no-till planting systems. With these systems, the banded fertilizer is applied in the fall of the previous crop year. Since the location of the band is known, the subsequent corn crop can be planted directly above it.
For these planting systems, rates of suggested P and K are adjusted based on soil test levels. When considering phosphate, the rates suggested for banded placement in conventional tillage systems are appropriate.
In contrast to phosphate, higher rates of potash are needed for banded application in conservation tillage production systems. If the soil test for K is in the range of 120-160 ppm in these systems, an annual application of 40 lbs. K2O/acre is suggested. If the soil test for K is less than 120 ppm, an annual application of 80 lbs. K2O/acre is suggested.
Annual applications of banded phosphate and K are suggested when corn follows corn. In a corn-soybean sequence, they can easily be applied in the fall of the soybean year, and the suggested rates can be doubled and applied for two years of production.
Editor's Note: George Rehm is a nutrient management specialist, recently retired from the University of Minnesota.