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North Dakota Fertilizer Recommendation Tables and Equations (SF882 (Revised))

The soil test recommendation tables here are based on field research data obtained in North Dakota, South Dakota, western Minnesota and the Canadian Prairie Provinces.

D.W. Franzen, NDSU Extension Soil Specialist


The following soil test recommendation tables are based on field research data obtained in North Dakota, South Dakota, western Minnesota and the Canadian Prairie Provinces. In the case of some crops, data in the literature alsowere used to supplement data available from this area.This publication contains changes from previous publications. Please dispose of older editions. Changes to tables were based on new or re-evaluated data.

The major changes from previous versions of this publication are in sunflower fertility recommendations.

Recommendation Tables

Fertilizer needs should be determined after evaluating the current fertility level of the soil through soil testing, preferably using a site-specific zone sampling approach, and the nutrient needs of the crop to be grown, and knowing the historic productivity of the soil. The yield potential must be based on historical yield productivity for a field or the immediate area.

Recent research has shown that more productive areas of fields require less fertilizer, particularly nitrogen (N), than less productive areas of the field because they tend to be higher in organic matter, have greater seasonal moisture content, and tend to use existing and applied nutrients more efficiently. The exception to this would be saline areas that are commonly high in residual N.

Several of our N recommendations are “capped” at a maximum rate. In years that support higher yields than our N recommendation formulas indicate, our data show that greater N release from the soil will support these higher yields without requiring supplemental N fertilizer greater than capped rates. In addition, sunflower N recommendations are capped due to greater lodging risk as N rate increases.

Nitrogen

Nitrogen (N) recommendations for most crops except some legumes are based on the amount of nitrate N (NO3-N) in the top 2 feet of soil and the yield potential. Omission of the 2-foot nitrate-N analysis results in random numbers for the N recommendation. The 2-foot nitrate-N soil test is extremely important in this region for optimal N recommendations and to promote N-use efficiency, greater farm profitability and environmental stewardship.

Nitrogen fertilizer recommendations are not adjusted based on method of placement, but they are adjusted for previous crop and depth of sampling. To determine the amount of recommended fertilizer N, subtract the amount of NO3 N in the soil as determined by soil test and N-credit from the previous crop, if applicable, from the total amount of available N needed for a particular yield goal and crop.

Spring wheat, durum, corn and sunflower N recommendations include economic modifiers to rate based on an economic production function that combines yield/quality increases/decreases with nutrient rate and the cost of nutrient input to indicate the N rate that will provide the grower with the greatest net economic return.

Example of the use of soil test N in canola:

The soil test indicates that 55 pounds of NO3 N are present in the soil to 2 feet. The chart in Table 6 indicates a recommendation of 130 pounds N per acre total requirement. The amount of N to apply would be 130 less 55, or 75 pounds N per acre.

Adjusting N Recommendations

In a preplant NO3 N soil testing program, certain adjustments need to be made for the expected but unseen from a fall or spring soil test NO3-N analysis contribution of N from some previous crops.

Previous Crop N Credits

Some crop residues have a lower carbon-to-nitrogen (C/N) ratio than others, which results in a release of plant-available N through rapid decomposition. Also, the mass of residue of some crops is less than others (dry bean compared with wheat or corn, for example). Evidence also indicates that some crops (soybeans) may accelerate the normal N mineralization rate from organic matter.

Nitrogen availability is greater following crops with a lower C/N ratio (sugar beet, alfalfa) and crops having a lower mass of residue (soybean, dry bean) with less ability to tie up N during decomposition.

The following N credits should be subtracted from crop N recommendations based on comparative subsequent crop N rate response. The values in the Credits table come from North Dakota and Minnesota experiments.

Crop N Credits

Second-year N Credits

Half of the N credit indicated for the first year for sweet clover and alfalfa is recommended, but no N credit is recommended after the second year for other crops.

Depth Adjustments

The original data for calibration of the NO3-N test was based on soil samples taken to a depth of 5 feet. Sampling beyond 2 feet improved nitrogen recommendations somewhat, but in the late 1960s, researchers decided that the extra effort to sample to a depth of 3 or 4 feet was not practical or necessary for most crops.

Drought and application of excess N, however, may result in a buildup of available N below 2 feet. When fields are tested for N each year and only the recommended amount of N is applied, an accumulation of nitrogen below 2 feet is unlikely unless N is not utilized by the crop due to drought.

Sugar beet is the most likely crop to be sampled to the 4-foot depth, but adjustments are not necessary in N calculations. Sugar beet N recommendations for 2-foot and 4-foot samplings are provided in Table 24. If deeper sampling is conducted to refine recommendations or screen for problems in malting barley, sunflower or safflower, the following adjustments would apply:

If the amount of NO3 N in the 2- to 4-foot depth is less than 30 lb NO3 N/acre, do not adjust the recommendation.

If the amount of NO3 N in the 2- to 4-foot depth is more than 30 lb NO3 N/acre, reduce the N recommendation by 80 percent of the amount greater than 30 lb/A. For example, if 50 lb of NO3 N/acre are present at the 2- to 4-foot depth, reduce the N recommendation by 16 lb N/acre, or 80 percent X (50 lb N/acre less 30 lb N/acre, or 20 pounds).

Phosphorus and Potassium

The phosphorus (P) and potassium (K) recommended in these tables is the amount to be applied as a broadcast application. Because banded fertilizer generally is used more efficiently in the year of application, the amount of P2O5 and K2O in the tables can be reduced by one-third when banding and still result in similar yield to the full broadcast fertilizer rate.

Data from field trials in drier or cooler years indicate that small grains, corn and canola will respond to seed-placed or side-banded P fertilizer, even on soils testing medium to high in phosphorus.

Some crops are very sensitive to fertilizer salt injury. No fertilizer is recommended with the seed for these crops in 15-inch rows or wider. Fertilizer-sensitive crops include all legumes, such as soybean, pea and dry bean. Consult individual soil fertility publications for each crop for more information. For information regarding fertilizer rate limits with the seed in small grains, refer to NDSU Extension publication SF1751, available online.

Under no-till and ridge-till systems, corn has responded to banded K even when soil test levels for K are high.

Broadcast recommendations of P or K for low- and very-low-testing soils include buildup P and K rates. When rates are reduced, soil test levels are not increased through time.

A long-term P and K strategy should include buildup to high (critical) soil test levels at some future date. Near maximum yield potential is achieved only when these soil test levels are reached. Application of less than maintenance rates will result in a decline in P and K levels through time and an accompanying decline in the productivity of most crops.

Sulfur

Sulfur (S) deficiency most likely will occur on sandy soils throughout North Dakota and on well drained, medium textured soils. However, in wet seasons, S deficiency has been seen on clay soils with an organic matter content greater than 5 percent. Sulfur deficiencies appear most often on higher landscape positions with a thin-surface organic-matter layer (“A” horizon) and coarse soil texture (loam to sand and gravel), but having S deficiency is possible on almost any nonsaline soil should the seasons be wet.

Our current S soil test characterizes the S status of the soil very poorly. The test commonly underestimates or overestimates the available S in soil for a variety of reasons. Noting the texture, organic matter content, landscape position and rainfall in the past year often is a better predictor of S need than soil testing.

In a year following a high rainfall/snowfall year, applying some 10 to 20 pounds S/acre regardless of landscape position, soil texture or organic matter may be prudent. Since 2014, serious S deficiency appeared in many fields that we used to think would be adequate in S. The sulfur source should be sulfate- or thiosulfate-based and not elemental S of any kind.

Chloride

The chloride (Cl) soil test is calibrated only for small grains, although a few responses also have been seen in corn within the U.S. In general, responses to Cl in small grains have been in the range of 1 to 6 bushels per acre on responsive sites.

The Cl recommendation is determined by subtracting the amount of Cl found in the top 2 feet of soil from 40 lb/acre, although most of the yield response is the result of the first 10 to 15 lb/acre of Cl applied. The most commercially available and cheapest source of Cl fertilizer is 0-0-60 (potassium chloride, muriate of potash), which contains approximately 50 percent Cl.

Other Nutrients

The DTPA (diethylenetriaminepentaacetic acid) soil test analysis is used in North Dakota to analyze soils for plant-available zinc (Zn), iron (Fe), manganese (Mn) and copper (Cu). Calibration data in North Dakota are available only for Zn on the crops known to respond positively to Zn application in the state, which are corn, potato, flax and dry edible bean (not soybean), and for Cu on wheat/durum and barley.

Micronutrient requirements are crop-specific. Additional crops would not be expected to respond to Zn or Cu if not listed above. The Cu soil test has been useful only in the state if the soils are less than 2.5 percent organic matter in deep sandy soils, such as an eroded Arvilla soil.

Zinc

When corn, potato, flax or dry edible beans are to be grown on a field testing low to very low in Zn, the recommendation is to apply 10 lb/acre of Zn as zinc sulfate in a broadcast application, or one-third of that rate in a seed-placed or near-seed band. Zinc is especially required in these crops if high levels of broadcast P or a starter P fertilizer is applied when soil Zn levels are low. The water solubility of the Zn fertilizer is important in efficient dispersion and uptake.

Also, the crop is more likely to achieve a first-year response to zinc sulfate if the fine granular formulation of the product is used instead of the MAP (mono-ammonium phosphate)- or DAP (diammonium phosphate)-sized granules usually available.

A fine granular application should be made using a fine-granular applicator similar to those used in the past to apply granular herbicide formulations. The distribution of large granules may not be adequate to supply all plants with Zn if low rates are applied.

A broadcast application of zinc sulfate should correct a Zn deficiency for four to five years. Zinc chelates at suggested manufacturer rates also may be used but are relatively expensive per pound of plant food and offer no residual soil buildup.

Banded chelates at 1 pint to 2 quarts/acre can be applied near or with the seed at planting. Foliar applications of zinc chelate and other soluble Zn fertilizers at low rates are also effective for correction of deficiencies for a single season. No Zn is recommended on fields testing medium or above or on fields testing very low, low or medium if the crop to be grown is not a Zn-sensitive crop.

Iron

In general, the supply of soluble iron (Fe) to plants from soil is related to the soil carbonate level, which is important to determine if the field will be in soybean when the soil pH is over 7. If carbonates are present, soil wetness, cold soils, excessive tillage and high soluble salt levels influence the presence and severity of iron deficiency chlorosis (IDC).

Most of North Dakota crops are not sensitive to low available iron and are adapted to regional conditions. However, IDC has been seen in flax, field pea and dry bean and is a particularly serious problem in soybean.

Seed treatment with ortho-ortho-FeEDDHA (iron-ethylenediaminedi (o-hydroxyphenylacetic) acid) has provided the most consistent soybean yield increases in IDC- susceptible soils. It should be seed-placed in a band as directed on the label for greatest effectiveness.

Other Fe fertilizers, including ortho-para-FeEDDHA, are far less effective. Yield increases to ortho-ortho-FeEDDHA also have been seen in sugar beet in the absence of IDC in multiple trials. Foliar applications have not been effective in correcting IDC and achieving similar yield to a seed-placed o-o-FeEDDHA band.

The best solution on fields with IDC is to plant varieties that are more tolerant, and avoiding soybean cultivation on soils with high IDC potential and that are high in soluble salts. Researchers at NDSU have rated about 200 soybean varieties each year for the past 10 years for IDC tolerance.

Manganese

No field responses to manganese in North Dakota have been documented. Therefore, a recommendation is not made for any soil test level.

Copper

Yield increases due to soil-applied copper were documented in North Dakota; however, the responses were on low-organic-matter, loamy sand soils with low (less than 0.3 parts per million) copper levels. A number of companion trials on similar soils resulted in no yield increase.

At best, copper should be applied only to low-organic-matter, sandy soils with low copper levels, but expect a success rate of about 15 percent. Copper fertilizers are expensive, and their use should be based on weighing the productivity of responsive soils with the low return of benefits if copper were applied.

Fertilization Recommendation Tables for Crops Commonly Grown in North Dakota

The following tables can be used for the yield potentials shown.

For other yield potentials, use the equations at the bottom of each table.

The abbreviations used in the tables are:

  • YP = yield potential
  • STN = soil test nitrogen
  • STP = soil test phosphorus
  • STK = soil test potassium
  • PCC = previous crop credit

Table 1


Table 2
Table 3

Table 4a

Table 4b
Table 5A
Table 6
Table 7
Table 8

Tables 9-1 through 9-10. Corn for grain.

For a simpler method to determine N rates for corn, see the North Dakota Corn N calculator .

Table 9-1

Table 9-2
Table 9-3
Table 9-4
Table 9-5
Table 9-6
Figure 9-7
Table 9-8
Figure 9-9
Table 10

Table 11

Table 12
Table 13
Table 14
Table 15
Table 16
Table 17
Table 18
Table 19
Table 20
Table 21
Table 22
Table 23
Table 24

Tables 25-1 through 25-3. Sunflower. See Figure 2 for map of regions.

Table 25-1

Table 25-2
Table 25-3

Tables 26-1 through 26-9.
Spring Wheat and Durum Nitrogen Recommendations

To determine recommended N rate:

1. Find the region of the farm and look up the gross optimal available-N from the appropriate region/productivity table (Tables 27-1 through 27-9).
2. Subtract the soil test nitrate-N from the 0- to 2-foot depth.
3. Subtract any previous crop N credits.
4. Consider whether the field has been in a no-till or one-pass tillage system.

  • If the field has been in no-till less than five continuous years, add 20 lb N/acre.
  • If the field has been in no-till five or more continuous years, subtract 50 lb N/acre.

5. Make an organic-matter adjustment for soils with greater than 5.9 percent organic matter.

  •  For each full percent of organic matter greater than 5 percent, subtract 50 lb N/acre.

For easier N rate determination, see the North Dakota Spring Wheat and Durum N Calculator.

The final N rate may be adjusted plus or minus 30 lb N/acre due to a host of factors, including varietal protein traits, soil that tends to favor denitrification or leaching losses, excessive straw from the previous year or less than ideal application methods.

Within each region, the productivity is defined.

Productivity category definitions:

Langdon Region
Low = less than 40 bu/acre
Medium = 41 to 60 bu/acre
High = greater than 60 bu/acre

Eastern Region
Low = less than 40 bu/acre
Medium = 41 to 60 bu/acre
High = greater than 60 bu/acre

Western Region
Low = less than 30 bu/acre
Medium = 31 to 50 bu/acre
High = greater than 50 bu/acre

 

Table 26-1
Table 26-2 SW/durum low productivity
Table 26-3
Table 26-4
Table 26-5
Table 26-6
Table 26-7
Table 26-8
Table 26-9

Table 26-10

Table 27Warmer and drier, Cool and Moister

Figure 1. General climatic delineation between cooler and moister areas in North Dakota compared with warmer and drier areas.

In a given year, the line separating the two regions may move considerably east or west.

For use with Tables 4a, 4b and 6.

(Image courtesy of NASA, Angela King, image compiler, and Hobart King/Geology.com, publisher).

Agri-climatology regions

Figure 2. Agri-climatology regions for use in Tables 26-1 through 26-3 for sunflower and Tables 27-1 through 27-9 for spring wheat and durum N recommendations, and Table 28 for winter wheat considerations.

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