Fertilizing barley in Minnesota

There are two approaches to arriving at fertilizer N guidelines for barley. One approach is to base guidelines for fertilizer N on the results of the soil nitrate test. The soil nitrate test is recommended for western Minnesota. When the soil nitrate test is used, the amount of fertilizer N needed to meet the yield goal is calculated from the following equations. 

Nitrogen fertilizer formula for malting barley

Suggested N in lb/acre = [(1.5) x YG] - STN_{(0-24 in.)} - N_PC

Nitrogen fertilizer formula for feed grain barley

Suggested N in lb/acre = [(1.7) x YG] - STN_{(0-24 in.)} - N_PC

Nitrogen formula variables

• YG = yield goal, bushel per acre
• STN_{(0-24 in.)} = nitrate-nitrogen (NO₃^--N) measured to a depth of 2 feet, lb per acre.
• N_PC = amount of N supplied by the previous crop, lb per acre

Use the credits in the following table when the soil nitrate test is used.

*If the third or fourth cutting was not harvested, add 20 lb N/acre to the N credits listed.

Nitrogen credits should also be used when barley is grown in the second year after any of the legume crops listed above. For these situations, use the N credit listed in the following table.

The soil nitrate test is integral as a nitrogen management tool. The soil samples needed for measurement of carryover NO₃^--N can be collected in either fall or spring. It is usually easier to collect samples in early fall. If possible, delay sampling until the soil temperature drops below 50° F.

The amount of fertilizer N needed can also be based on yield goal, previous crop and soil organic matter content. 

Nitrogen from the decomposing tops of a previous crop of sugar beet can be used by the barley crop when it follows in a rotation. These N credits are based on the overall color of the sugar beet tops at harvest. If the soil nitrate test is used, the value for the appropriate color should be used as the nitrogen credit from the previous crop (NPC) in the N guideline equation.

If the N suggestions are taken from the following table, subtract the value for the appropriate color from the appropriate N suggestion listed in the first table.

The nitrogen supplied by legume crops can also be used by the barley crop if it is planted two years after the legume. The nitrogen credits for these situations are summarized below. Subtract these values from the nitrogen suggestions that are listed for crops grown in Group 2 for the appropriate yield goal.

*Based on the expected yield of the crop in bushels per acre.

**Low = less than 3.0%; Medium/High = 3.0% or more

• Crops in Group 1: Alsike clover, birdsfoot trefoil, grass/legume hay, grass-legume pasture, fallow, red clover.
• Crops in Group 2: Alfalfa (0-1 plants/ft.²), barley, buckwheat, canola, corn, flax, grass hay, grass pasture, oat, potato, rye, sorghum-sudan, sugar beet, sunflower, sweet corn, triticale, vegetables, wheat.

Research has shown that most of the total amount of essential nutrients used by barley is absorbed from the soil between the tillering and heading growth stages. So it is important to have an adequate supply of all nutrients in the root zone early in the growing season.

Since N is mobile in soils and can move to the roots with soil water, there can be considerable flexibility in the management of this important nutrient.

Fertilizer N can be applied in the fall for barley production in most of Minnesota. There are some exceptions.

• Do not apply fertilizer N in the fall when soils are sandy.
• Split applications are encouraged for very sandy soils.
  • The first application can be made before planting.
  • The remainder should be applied at or near tillering.
• In southeast Minnesota, apply fertilizer N in the spring and incorporate it before planting. Do not apply fertilizer N in the fall in the region.

Split N applications are strongly encouraged when irrigated barley is grown on sandy soils. For this production system, some N should be applied before planting and combined with an N application at the tillering to early boot stage. The ideal percentage of total N to use at each application has not been determined. It may be practical to apply half of the total N needed before planting and the remaining half at the tillering to early boot stage.

If applied properly, all common N fertilizer sources will have an equal effect on wheat yields. Some precautions in the application of some N sources are necessary.

With anhydrous ammonia (82-0-0), there is a concern for loss during application. If there is a strong ammonia odor emanating from the field, further application is discouraged since significant losses are likely to occur with application.

There is also a potential for N loss if urea (46-0-0) or urea-ammonium nitrate (28-0-0) is broadcast on the soil surface without incorporation when soil pH is higher than 7.3, air temperatures are 50^o F or higher, and there is residue on the soil surface. Shallow incorporation of urea or fertilizers containing urea within 48 hours of application is encouraged when these N sources are used for wheat production.

Fall application of 28 or 32% UAN is strongly discouraged due to a portion of the N in the fertilizer already in the nitrate form at application.

Urea-ammonium nitrate solution (28%) can be applied either before planting or post-emergence. A foliar application may cause some leaf burning, but there will be no reduction in yields if reasonable rates up to 30 pounds N per acre are used unless the N is applied using streamer bars. Leaf burn may be excessive if foliar N rates exceed 60 pounds N per acre.

The use of air seeders has increased in popularity in recent years. Many seeders are equipped to apply a mixture of seed and dry fertilizer at the time of planting. There are, however, no firm guidelines for the amount of fertilizer that can be applied with the seed with this planting equipment.

The amount of fertilizer that can safely be applied with an air seeder depends on the row spacing and the amount of area the seed and fertilizer are spread over, and soil factors such as soil texture, cation exchange capacity, and pH. As row spacing increases the amount of fertilizer that can safely be applied decreases since the concentration in the band increases.

The amount of N + K₂O should be kept at a minimum and less than 30 pounds per acre of N + K₂O combined as a general practice to minimize the risk of stand loss. But these rates can vary based on many factors such as the soil type, soil moisture at planting, and the volume of soil the fertilizer is applied in. Rates should be reduced if soils are dry at planting.

By contrast, high rates of P₂O₅ per acre generally do not hinder germination if mixed with wheat seed planted with an air seeder.

Fertilizer can present a significant risk of seedling damage when placed in contact with the seed. The next table summarizes the maximum rates of N that can be applied, assuming that soils are not dry at planting, adjusted for planter spacing, and the amount of seedbed used for fertilizer application.

If soils are dry at planting, rates should be reduced to the low end of the suggested range or less to decrease the risk of seedling damage.

* Table adapted from Deibert, E.J. 1994. Fertilizer Application with Small Grain Seed at Planting. N Dakota State Univ. Ext. Publ EB-62.

The maximum nitrogen rate applied with the air seeder also must be adjusted based on soil texture. The next table summarizes the maximum suggested rates of N for soils with different textures based on the method of application.

Loamy sands and sandy loams present the greatest risk for seedling damage as these soils contain less available water than clay loams and clays. Extreme care should be taken when applying fertilizer with the seed on sandy soils when fertilizer is banded in a narrow band with the seed since this presents the highest potential for seedling damage.

It is important to remember that crops can differ in their tolerance to seed-placed fertilizers, so the suggestions outlined should not substitute for sound judgment when making decisions on the amount of fertilizer applied with the seed.

*Table adapted from Deibert, E.J. 1994. Fertilizer Application with Small Grain Seed at Planting. N Dakota State Univ. Ext. Publ EB-62.

The phosphorus (P) status of Minnesota soils is determined by using either Bray or Olsen analysis. These tests are an index of crop response and not a direct measure of the amount of P in the soil.

The Bray soil test uses a strong acid to extract phosphorus from the soil. In situations where carbonates are present in the soil, the acid can be neutralized reducing the amount of P extracted and the effectiveness of the test.

The Olsen test provides more accurate results if the soil pH is 7.4 or greater as it is not affected by carbonates in the soil.

Both tests can be used accurately in situations where high soil pH is not an issue, but values from the Olsen tests will be lower for the same soil test classification range since the Bray and Olsen tests extract P out of different pools of available P in the soil.

The phosphate suggestions change with soil test level and placement. At very low, low, and medium soil test levels, the needed phosphate can be broadcast and incorporated before planting or applied with the drill at planting. Rates can be reduced by 50% if the phosphate fertilizer is applied with the drill. 

No broadcast phosphate is suggested when the soil test for P is high (Bray = 16-20 ppm P; Olsen = 12-15 ppm P). A small amount of phosphate applied with the drill is suggested for these situations.

No phosphate fertilizer will be needed when the soil test for P is in the very high range (Bray = 21+ ppm P; Olsen = 16+ ppm P) unless soils are cold and wet at planting. In north-central Minnesota, soils may be cold and wet at planting time. Even though the soil test for P may be high, some phosphate fertilizer (10 lb P₂O₅/acre) placed in a band near the seed may improve barley yields on these soils.

*Pounds of P₂O₅ suggested to apply per acre for barley production based on either the Bray-P1 or Olsen soil methods test reported in parts per million (ppm). Use one of the following equations if a phosphate guideline for a specific expected yield and a specific P soil test is desired.

• P₂O_{5 rec} = [0.785 - (0.039) (Bray P, ppm)] (Expected Yield)
• P₂O_{5 rec} = [0.785 - (0.050) (Olsen P, ppm)] (Expected Yield)

As with phosphate, the soil test represents an index of availability and is not a direct measure of potassium in the soil. Suggestions vary with placement and soil test level for K.

• No broadcast potash will be needed when the soil test K is 121 ppm or greater.
• No potash (either banded or broadcast) is suggested when the soil test for K is 161 ppm or greater.

It may not be practical to broadcast low rates of phosphate and potash. It may be more practical to double the suggested broadcast rate and apply in alternate years if the grain drill is not equipped to apply fertilizer with the seed. 

Any phosphate or potash that is broadcast should be incorporated before seeding. These nutrients do not move in most soils and will have very little effect on production if they are top-dressed to an established stand. Application before a primary tillage operation is preferred.

Fertilizing with the drill

Since most of the small grain acreage in Minnesota is planted in early spring when soil conditions are cold and wet, the application of fertilizer with the drill should be a standard management practice. Plant root growth tends to be slow under these circumstances, which limits the uptake of immobile nutrients such as phosphorus and potassium. Placement near the seed ensures nutrients are readily available early in the growing season.

Caution:

• Do not place ammonium thiosulfate (12-0-0-26) in direct contact with the seed.
• Do not place boron fertilizers in direct contact with the seed.
• Phosphate in fertilizer has no negative effect on seed germination and seedling growth, so ample amounts of phosphate can be placed in contact with the seed.

Use the following equation for a potash guideline for a specific expected yield.

K₂O rec = [1.286 - (0.0085) (K soil test)] (expected yield).

Use the following equation if a potash recommendation for a specific soil test and a specific yield goal is desired.

• K₂ORec = [1.286 - (.0085) (K soil test), ppm] (yield goal)
• No potash fertilizer is suggested when the K test is 161 ppm or greater.

Sulfur (S) can increase barley yields when the crop is grown on sandy soils. Research trials have shown no need to add S to a fertilizer program when barley is grown on fine-textured soils in Minnesota.

The broadcast application of 25 pounds of sulfur per acre in the sulfate form will be adequate for growing barley when S is needed. For more efficient applications, use 10-15 pounds S per acre with the drill at planting. The sulfate form is suggested for this method of application.

Copper (Cu) may be required in a fertilizer program when barley is grown on organic soils. These suggestions are for organic (peat) soils only. The use of copper is not currently suggested when barley is grown on mineral soils.