WW-07425 Reviewed 2009
Copyright © 2002 Regents of the University of Minnesota. All rights reserved.
Profitable corn yields are the result of the wise use of several production inputs. Effective, but not excessive, use of fertilizer is just one part of the crop production puzzle. Fertilizer management involves more than selection of an appropriate rate. Choice of placement is a major consideration. This is especially true for the immobile nutrients (phosphorus, potassium, zinc).
There are various choices for fertilizer placement, and some terms can be confusing. The various placement options are briefly described as follows:
Compared to broadcast and incorporated fertilizer, the banded application keeps contact between soil and fertilizer to a minimum. This reduces fixation or “tie up” of phosphorus and potassium in the soil. Fixation of phosphorus varies with soil pH. In very acid soils (pH <5.0), the fixation occurs as insoluble iron and aluminum phosphates. In calcareous soils (pH >7.4), the fixation takes place as insoluble calcium phosphates.
The “tie up” of potassium does not vary with soil pH. Instead, the type of clay in the soil is important. Potassium fixation is affected by a variety of clays. The soils in southeastern Minnesota contain substantial amounts of clay that fix potassium. By contrast, the types of clays which fix K are not dominant in the soils in western Minnesota.
Since reduced contact between soil and fertilizer reduces the fixation or “tie up” of phosphorus and potassium, these nutrients are used more efficiently by crops such as corn and small grains if applied in a band. This principle has not been verified by field trials with soybeans. For corn, improved efficiency allows for the use of reduced rates of phosphorus and potassium when those nutrients are applied in a band. The difference in recommended rates of phosphate and potash as affected by placement (band, broadcast) for corn production is shown in Tables 1 and 2, respectively. The use of lower rates of phosphorus and/or potasssium in a band reduces the amount of money spent for phosphate and/or potash fertilizers.
|Soil Test P (ppm)|
|v. low||low||med||high||v. high|
|bu./acre|| lb. P2O5/acre to apply |
|Soil Test K (ppm)|
|v. low||low||med||high||v. high|
|bu./acre|| lb. K2O/acre to apply |
Yield evidence for the effectiveness of phosphate and potash applied in a band is provided in Tables 3 and 4, respectively. The studies with phosphate were conducted at the Southwest Research and Outreach Center, Lamberton. The research with potash was conducted in fields of cooperating farmers in Goodhue County.
|P2O5Applied||Placement||Yield Average of two years|
|* Treatment averages followed by the same letter are not significantly different at the .05 confidence level.|
Soil test P was low.
|K2O Applied||Placement||Yield Average of two years|
|Treatment averages followed by the same letter are not significantly different at the .05 confidence level.|
Soil test K was low.
There is no firm rule which dictates where the banded fertilizer should be placed in relation to the corn seed. The fertilizer supplying phosphate and/or potash can be placed 1) to the side of, 2) to the side of and below the seed, or 3) below the seed. Phosphorus and potassium are considered to be immobile in soils. Therefore, crops will get little benefit from these nutrients if they are placed or applied above the level of the seed either at the time of planting or after planting.
The placement of the immobile nutrients in a band below the seed is a highly recommended practice when corn is grown in ridge-till and no-till planting systems. This banded placement is frequently referred to as a “deep band.”
In Minnesota, this deep band or subsurface band is usually applied in the fall of the soybean year in the rotation. The corn can be planted directly above this band. This placement of the immobile nutrients substitutes for the use of a starter fertilizer.
Recommendations for rate of phosphate needed with this placement option are the same as the rates suggested for starter application (Table 1). Compared to conventional tillage systems, higher rates of potash are needed for corn planted in the conservation tillage production systems. If soil test values for K are in the range of 100 to 180 ppm, a rate of 40 to 50 lb. K2O per acre per year is suggested for the corn/soybean rotation. This annual rate can be doubled and applied in the fall of the soybean year and will be satisfactory for two years of production. If soil test values for K are less than 100 ppm, an annual banded application of 80 lb. K2O per acre is suggested for the conservation tillage production systems.
Placement of a fertilizer near the seed at planting is the more traditional use of banded fertilizer. The early planter attachments were engineered to place the fertilizer two inches to the side of and two inches below the seed. This specific placement is not essential for the use of a starter fertilizer. It is important to place this starter band below the level of the seed. The distance between the seed and fertilizer, however, can vary from one to three inches. Some of the starter effect is lost if the banded fertilizer is placed more than three inches from the seed. A minimum distance between seed and fertilizer of one inch is suggested to assure crop safety.
There can be some damage to germination and emergence if excessive amounts of nitrogen and/or potash are placed too close to the seed. Phosphate has no negative effect on germination. Therefore, the amount of phosphate needed for optimum yield can be applied in a band near the seed if the amounts of either nitrogen and/or potash applied with this phosphate are not too high. The amount of nitrogen applied within one inch of the seed should be less than 30 lb. per acre. If applied within one inch of the seed, rates of K2O up to 60 lb. per acre can be used. If higher rates of K2O are needed to meet recommendations, the distance between seed and fertilizer should be more than one inch.
The placement of fertilizer with the seed (pop-up) is an old concept that has become more popular in recent years. This is an excellent placement option for growers who have large planters and cannot use the conventional starter attachments. This placement option is also well suited for fields that a medium level of soil test P and/or K. In the medium range, small rates of phosphate and/or potash are recommended.
Recent research conducted in Minnesota was designed to measure the effect of application of three rates of three fluid fertilizers applied in contact with corn seed on emergence and yield. A control (no pop-up used) was also included. The study was conducted at both the Southern Research and Outreach Center, Waseca, and the Southwest Research and Outreach Center, Lamberton.
The average effect of “pop-up” fertilizer on emergence is summarized in Table 5. Except for the application of 7-21-7 at a rate of 15 gallons per acre, none of the fluids studied had a negative effect on emergence. The values shown in Table 5 are averages for several locations over a period of three years.
The average corn yields from the same study are summarized in Table 6. Compared to the control, none of the fluids applied had a negative effect on yield. Even though the sites selected had high soil test values for P and K, there was a small, consistent increase in yield when the 10-34-0 was applied in contact with the seed. The stand reduction caused by the use of the highest rate of 7-21-7 was not reflected in yield.
|Fertilizer Grade||Rate of Application (gal./acre)|
| % of control* |
|* control = no fertilizer applied with the seed|
|Fertilizer Grade||Rate of Application (gal./acre)|
| bu./acre |
There was ample moisture in the seed zone at planting at both locations. With this amount of moisture, rates of 10-34-0 up to 10 gallons per acre should be safe for corn planting in Minnesota. If soils are dry at planting, some damage from the use of “pop-up” fertilizer might be expected.
There’s no easy method for measuring soil moisture content in the field. Squeezing the soil taken from the planting depth in the palm of the hand and then releasing is a useful test. The appearance of soils with a sandy or clay loam texture associated with various water-holding capacities is shown in Figures 1A and 1B.
Soil particles will stick together as water is added to the soil. The water-holding capacity of sandy soils is low and small changes in the percent of water-holding capacity filled with water produce major changes in the appearance of soil in the hand (Figure 1A). In Minnesota, soils with a silt loam, silty clay loam, and clay loam texture are described as being fine-textured. These fine-textured soils stick together as the percentage of water-hold capacity filled with water increases (Figure 1B). When more than 50% of the water-holding capacity is filled with water, it’s easy to form a “ribbon” of soil between finger and thumb.
In Minnesota, the greatest risk of damage from “pop-up” fertilizer will occur with the sandy soils. With the fine-textured soils, potential for damage from “pop-up” fertilizer is reduced substantially if the moisture content is higher than 25% of the water-holding capacity.
There’s a continuing debate regarding liquid and dry fertilizers when used in a band. Research shows that yields will be equal if a fertilizer with the same analysis is applied in either a liquid or dry form. Decisions about the use of liquid or dry materials placed in a band should be based on such factors as price, preference for handling, and availability of equipment needed for handling. Growing plants do not have a preference for either liquid or dry materials.
In some cases, however, one form of starter may be better than the other. For example, the sulfur concentration in most liquid fertilizers is relatively low because of the chemistry involved in the manufacturing process. Therefore, higher rates of fluid materials are needed to supply the sulfur needs of corn grown on sandy soils. Dry materials can usually be blended so that a product with a higher sulfur concentration can be provided. In such situations, a dry starter is sometimes less expensive because it can supply the needed sulfur while being applied at a lower rate.
The “pop-up” placement is an effective method for application of phosphate and potash fertilizers. There are, however, some cautions with this placement. Urea (46-0-0) should not be applied in contact with corn seeds. This is especially true when the soil is dry.
The information summarized in Table 7 shows that 46-0-0 applied in the seed furrow in a dry sandy soil reduced germination and subsequent yield. By contrast, there was no yield reduction when the 46-0-0 was placed to the side of and below the seed at planting.
Ammonium thiosulfate (12-0-0-26) can also affect emergence if applied in contact with the seed. Contact of these fertilizers with corn seeds should be avoided.
|N Applied with Seed||Emerged Population||Grain Yield|
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