Cereals: Fertility Management

| Corn | Soybeans | Forages | Cereals | Dry Edible Beans |
| Spring and Winter Canola | Other Crops | Soil Management |
| Soil Fertility and Nutrient Use | Field Scouting |
| On-Farm Stored Grain Management | Weed Control |
| Insects and Pests of Field Crops | Diseases of Field Crops | Appendices |

Pub 811: Agronomy Guide > Cereals > Fertility Management

Order OMAFRA Publication 811: Agronomy Guide for Field Crops

Table of Contents

• Nitrogen
  • Table 4-13. Nitrogen Requirements for Cereal Crops
  • General Recommendations
  • Red Winter Wheats
  • Table 4-14. Nitrogen Requirements for Pastry Wheat
  • Nitrate-Nitrogen Soil Test for Spring Barley
    • Table 4-15. Nitrogen Recommendations for Spring Barley Based on Nitrate-Nitrogen Soil Tests
  • Uniformity of Nitrogen Fertilizer Application
• Table 4-16. Yield Loss Associated with Inaccurate Nitrogen Application Patterns
• Table 4-17. UAN as a Herbicide Carrier
• Timing of Nitrogen Application
  
• Phosphate and Potash
• Table 4-19. Phosphate Recommendations for Cereals Based on OMAFRA-Accredited Soil Tests
• Table 4-19. Potash Recommendations for Cereals Based on OMAFRA-Accredited Soil Tests
• Methods of Application
• Plant Analysis
• Table 4-18. Interpretation of Plant Analysis for Cereal Crops
• Micronutrients

Nitrogen

Cereals are members of the grass family and are very responsive to nitrogen. Over-application of nitrogen causes lodging in cereal crops, resulting in reduced yield, quality and harvestability Plate 24. The optimum rate of nitrogen for a particular field will depend on the crop being grown, past applications of manure or fertilizer to the field, soil type and crop rotation. Use general recommendations as a starting point but combine them with observations of crop growth and lodging tendency.

Plate 24. Lodging due to overlaps and/or excessive rates of nitrogen fertilizer.

¹ Where manure is applied or the preceding crop is a legume sod, reduce the nitrogen rates as shown in Table 9-7, Adjustment of Nitrogen Requirement, Where Crops Containing Legumes Are Plowed Down, and Table 9-8, Typical Amounts of Available Nitrogen, Phosphate and Potash From Different Types of Organic Nutrient Sources.
² See Nitrate-Nitrogen Soil Test for Spring Barley.
³ When not in rotation with tobacco.

General Recommendations

General nitrogen fertilizer recommendations for cereal crops are given in Table 4-13, Nitrogen Requirements for Cereal Crops, Table 4-14, Nitrogen Requirements for Pastry Wheat, and Table 4-15, Nitrogen Recommendations for Spring Barley Based on Nitrate-Nitrogen Soil Tests.

Red Winter Wheats

The current recommended hard red winter wheat varieties in Ontario are not equivalent to Canadian Western Red Spring Wheat (CWRS) but are mid-strength or blend varieties with bread-baking and other unique qualities. High protein content may be required in these varieties to meet quality specifications. To achieve these protein levels, a higher rate of nitrogen fertilizer is often required. Limited field research would suggest that the optimum rate of nitrogen is 30-45 kg/ha (27-40 lb/acre) greater than for pastry (soft) wheat. Splitting nitrogen applications may increase protein, but often these increases are small enough that the split application is not economical.

Newer hard red varieties are constantly being evaluated. These varieties may not require increased nitrogen to achieve protein levels that maximize protein premiums.

For soft red or soft white pastry wheat. The price ratio is the cost of the nitrogen in the fertilizer ($/kg N) divided by the selling price of the wheat ($/kg of wheat). See Appendix B, Corn Nitrogen Rate Worksheet (Imperial) With Detailed Explanation. A maximum of 10 kg N/ha may be applied at seeding and the remainder top-dressed in early spring.
Price Ratio Example: If the price of UAN is $350/T, then the price per kilogram of N is $350 ÷ 280 = $1.25/kg. The value of wheat at $250/T is $0.25/kg. The price ratio is $1.25 ÷ $0.25 = 5. In other words, it takes 5 kg of wheat to pay for 1 kg of nitrogen.

Check with seed suppliers for advice on nitrogen rates for specific varieties.

Nitrogen for grain protein production is required later in the development of the plant than the nitrogen for yield. This makes hard wheat varieties ideally suited to use the nitrogen from slow-release nitrogen sources or organic sources (legume plowdown or livestock manure). Desired protein levels are often easier to achieve on livestock farms due to these factors.

Nitrate-Nitrogen Soil Test for Spring Barley

The nitrate-nitrogen soil test can be used to predict nitrogen requirements for spring barley in areas other than Eastern Ontario that receive less than 3,000 CHUs see Figure 1-1, Crop Heat Units (CHU-M1) Available for Corn Production.
Since soils can vary greatly in their ability to supply nitrogen, the general recommendations found in Table 4-13, Nitrogen Requirements for Cereal Crops, may not be the most profitable for some fields. The amount of nitrate-nitrogen present in the soil near planting time can be a useful indicator of a soil's ability to supply nitrogen.

Consider a recommendation based on a spring nitrate-nitrogen test to be a useful guideline for formulating a nitrogen management program for spring barley Table 4-15, Nitrogen Recommendations for Spring Barley Based on Nitrate-Nitrogen Soil Tests.

100 kg/ha = 90 lb/acre

For areas outside of Eastern Ontario that receive less than 3,000 CHUs.

¹ To convert to nitrate-nitrogen soil test (30-cm depth) from ppm to kg/ha, multiply by 4.
² The price ratio is the cost of the nitrogen in the fertilizer ($/kg N) divided by the selling price of the barley ($/kg of barley). See Appendix B, Corn Nitrogen Rate Worksheet (Imperial) With Detailed Explanation.

Time and Depth of Sampling

Collect samples as close to planting time as practical (within 5 days of planting), allowing for sample shipping, analysis and receipt of results. Contact the accredited lab to determine sample turnaround times.

It is important that all cores in a field be taken to a 30-cm (12-in.) depth. To ensure that the sample is representative of the field, take the same number of cores and use a sampling pattern similar to that recommended for the standard soil test described in Soil Sampling. Also see Appendix C, Accredited Soil-Testing Laboratories in Ontario.

Where Caution Is Required

There are situations where the fertilizer recommendations based on nitrate-nitrogen soil tests should be adjusted. The nitrogen in manure or legumes applied or plowed down just before sampling will not have converted into nitrate and will not be detected by the soil test. Information will be provided with the soil test results on how to make appropriate adjustments.

Exercise caution if the recommendation is for large quantities of nitrogen and there is a history of barley lodging at lower rates of nitrogen. The nitrate-nitrogen soil test has not been adequately evaluated for:

• legumes or manure plowed down in the late summer or fall
• barley following legumes in a no-till system employing chemical burndown of the legumes

Uniformity of Nitrogen Fertilizer Application

To maximize yield, nitrogen must be applied uniformly across the field. Uniform application is more critical than the form of nitrogen fertilizer applied. Table 4-16, Yield Loss Associated with Inaccurate Nitrogen Application Patterns, shows the yield loss associated with inaccurate spread patterns. A 1.48-t/ha (22-bu/acre) yield difference was found between the fully fertilized and under-fertilized strips in the field.

Urea-Ammonium Nitrate Solution (UAN) (28-0-0 or 32-0-0) applied with streamer nozzles gives excellent, uniform nitrogen application and has shown small yield advantages (2.5 bu/acre) as shown in Table 4-17, UAN as a Herbicide Carrier. Urea or ammonium nitrate (calcium ammonium nitrate) can be applied using airflow technology, improving uniformity, although uniformity is not guaranteed. During humid days, urea can build up in the airflow tubes, restricting flow and affecting distribution. Be sure to maintain clear hoses to achieve a uniform spread pattern.

Spinner spreaders often have the greatest inconsistency in spread pattern. If spinners are employed, consider double spreading the field (i.e., 6-m or 20-ft centres at half the rate, instead of 12-m or 40-ft centres) to overcome this inconsistency.

UAN applied through streamer nozzles causes little or no leaf burn. Applying 28% nitrogen (UAN) as an overall broadcast treatment (using flood jet or tee-jet nozzles) to emerged cereal crops is Not Recommended. Table 4-17, shows the yield loss associated with this practice. The addition of 28% to a herbicide application, especially contact herbicides, will greatly increase leaf injury and yield loss Plate 25.

Sikkema, University of Guelph (RCAT), 2008, in progress

Plate 25. UAN 28% leaf burn. Applications of 28% nitrogen fertilizer can burn leaves and reduce yields.

Timing of Nitrogen Application

Most nitrogen fertilizers for spring cereals are applied before planting and worked into the soil. This allows optimum crop utilization of the fertilizer, while minimizing the risk of losses through run-off or volatilization. It is acceptable to top-dress emerged spring cereals, particularly if a starter fertilizer has been applied at planting.

Winter cereals should only receive a small application of nitrogen fertilizer at planting because of the risk of nitrogen loss overwinter. The majority of the nitrogen should be applied in early spring, just as the crop is beginning to green up. There is no consistent advantage to splitting the nitrogen applications on spring cereals or winter pastry wheat.

Phosphate and Potash

Phosphate and potash recommendations for cereals are in Table 4-19, Phosphate and Potash Recommendations for Cereals Based on OMAFRA-Accredited Soil Tests.

For information on the use of these tables, or if an OMAFRA-accredited soil test is unavailable, see Fertilizer Recommendations.

Methods of Application

Where phosphate fertilizer is required for cereal crops, it is best drilled with the seed. Seed-placed fertilizers may include some or all of the required nitrogen and potash, depending on rates of application. For further information, see Table 9-21, Maximum Safe Rates of Nutrients.

Plant Analysis

For cereals, sample the top two leaves at heading. Sample plants suspected of nutrient deficiency as soon as the problem appears. For plants less than 20 cm (8 in.) tall, sample the entire plant. For sampling at times other than heading, take samples from both deficient and healthy areas of the field for comparison purposes.

Take a soil sample from the same area and at the same time as a plant sample.

¹ Yield loss due to nutrient deficiency is expected with nutrient concentrations at or below the critical concentration.
² Maximum normal concentrations are more than adequate but do not necessarily cause toxicities.

For more information, see Table 4-18, Interpretation of Plant Analysis for Cereal Crops, and Appendix I, Diagnostic Services.

Micronutrients

Manganese

Manganese deficiency frequently occurs when wheat, oat or barley are grown in an organic (muck) soil. It can occasionally occur in mineral soils high in organic matter and soil pH, and in very sandy soils. On oat, manganese deficiency appears as irregular, oval, grey spots on the leaves Plate 26.

Plate 26. Manganese deficiency on oat looks like irregular, oval, grey spots.

On barley and wheat, it appears more commonly as a light yellow colour on the leaves with the veins in the leaf remaining slightly darker green see Plate 27.

Plate 27. Manganese deficiency on winter wheat (pale-yellow interveinal stripes on the leaves) occurs most frequently on high pH, sandy soils or on organic soils.

Both soil tests and plant analyses are useful in predicting where manganese deficiencies are likely to occur. Both analyses are available at the OMAFRA-accredited soil testing laboratories.

Correct the deficiency as soon as it is detected by a foliar spray of 2 kg/ha manganese from manganese sulphate (8 kg/ha manganese sulphate) in 200 L of water. Use a "spreader-sticker" in the spray. If the deficiency is severe, a second spray may be beneficial. Winter cereals growing in areas of severe manganese deficiency may require an application in the fall to ensure winter survival.

¹ HR, MR, LR, RR, and NR denote, respectively, high, medium, low, rare and no probabilities of profitable crop response to applied nutrient. Profitable response to applied nutrients occurs when the increase in crop value, from increased yield or quality, is greater than the cost of the applied nutrient.
² Where manure is applied, reduce the fertilizer application according to the amount and quantity of manure see Manure. For spring barley in an area with less than 2,800 CHUs, not manured and not following a legume sod, the nitrogen requirement is 70 kg/ha see Table 4-13, Nitrogen Requirements for Cereal Crops. If the soil test results are 11 for phosphate and 48 for potash, the phosphate requirement would be 50 kg/ha and the potash requirement 50 kg/ha. These nutrients could be supplied by drilling 250 kg (50 ÷ 20 x 100) of 5-20-20/ha to supply the phosphate and potash and broadcasting 170 kg of 34-0-0 or 130 kg of 45-0-0/ha to supply the recommended amount of nitrogen.
³ A rating of NR may mean reduced yield or affected nutrient balance in crops.
⁴ A rating of NR may mean reduced yield or quality of crops primarily due to magnesium deficiency. Natural levels above 250 occur occasionally on clay and clay loam soils but are not expected to cause problems because soils naturally high in potassium are usually high in magnesium.

Soil application is not recommended, regardless of source, because of the large amounts of manganese that would be required. In most cases, deficiencies in the plants are caused by a low availability of manganese from the soil rather than a lack of manganese. Adding more manganese to the soil will not often correct this.

Copper

Copper deficiency may occur in organic (muck) soils and is suspected on rare occasions in very sandy soils. The most common deficiency symptom is dieback from the tip of the leaf, often accompanied by twisting of the upper leaves. For information on correcting copper deficiencies, see Micronutrient Fertilizers, on page 161.

Boron

Boron deficiency has not been diagnosed in cereals. Boron applications can be toxic, causing a bleaching of leaf tissue in seedlings.

Zinc

Zinc deficiency in cereals does not appear to be a problem.

Do not apply mixtures of herbicides and foliar fertilizers to crop foliage unless recommended by competent authorities. Always consult the herbicide label.