Cereals: Fertility

Excerpt from Agronomy Guide for Field Crops (Chapter 6)

Order OMAFRA Publication 811: Agronomy Guide for Field Crops

Table of Contents

1. Fertilizers for Cereal Crops
   • Nitrogen
     • Nitrogen Requirements - Cereal Crops - Table 6-10
     • Nitrogen Requirements for Pastry Wheat - Table 6-11
     • Nitrogen Recommendations for Spring Barley Based on Nitrate-Nitrogen Soil Tests - Table 6-12
     • Yield Loss Associated with Inaccurate Nitrogen Application Patterns - Table 6-13
     • Yield Loss Associated With Leaf Burn From 28% Nitrogen Broadcast Treatment on Cereals - Table 6-14
   • Phosphate and Potash
     • Phosphate and Potash Recommendations for Cereals Based on OMAFRA-Accredited Soil Tests - Table 6-15
2. Plant Analysis
3. Interpretation of Plant Analysis for Cereal Crops - Table 6-16
4. Micronutrients
   • Manganese
   • Copper
   • Boron
   • Zinc
5. Updates on Cereals: Fertility
6. Related links...

Fertilizers for Cereal Crops

Nitrogen

| General Recommendations | Hard Red Winter Wheats | Spring Barley |
| Uniform Application | Leaf Burn | Timing |

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 difficulty in crop harvest.

Plate 101. Lodging due to overlaps and/or excessive rates of nitrogen fertilzer

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.

General Recommendations - General nitrogen fertilizer recommendations for cereal crops are given in Table 6-10, Nitrogen Requirements - Cereal Crops, Table 6-11, Nitrogen Requirements for Pastry Wheat, and Table 6-12, Nitrogen Recommendations for Spring Barley Based on Nitrate-Nitrogen Soil Tests. High rates of nitrogen from manure or manufactured fertilizers can cause lodging of cereals.

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100 kg/ha = 90 lb/ac

¹Where manure is applied or the preceding crop is a legume sod, reduce the nitrogen rates as shown in Table 2-15, Adjustment of Nitrogen Requirement Where Crops Containing Legumes Are Plowed Down and Table 2-16, Average Amounts of Dry Matter, Nitrogen and Available Phosphate and Potash for Different Types of Organic Nutrient Sources.
²See the section , Nitrate-Nitrogen Soil Test and Spring Barley
³Interim recommendation based on limited research.
⁴When not in rotation with tobacco.

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100 kg/ha = 90 lbs/ac

For soft red or soft white pastry wheat. Based on winter wheat valued at $142/tonne. A maximum of 10 kg of nitrogen per hectare may be applied at seeding and the remainder top-dressed in early spring.

¹Expected under your conditions of soil, climate and management.
²When not in rotation with tobacco.
³The most appropriate rate at time of printing.
⁴If your expected yield is 4.5 t/ha and nitrogen cost $.60/kg, the most profitable rate of application is 85 kg/ha of nitrogen.

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100 kg/ha = 90 lb/ac

For areas outside of Eastern Ontario that receive less than 2,800 CHUs.

¹To convert to nitrate-nitrogen soil test (30-cm depth) from ppm to kg/ha, multiply by 4.
²The 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 the section Nitrogen/Corn Price Ratio.

Recommendations for Hard Red Winter Wheats

The current recommended hard red winter wheat varieties are not true hard wheats. They are not equivalent to Canadian Western Red Spring wheat (CWRS) but are mid-strength varieties with bread-baking and other unique qualities. High protein content is 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/ac) greater than for pastry (soft) wheat. There is some indication that splitting the nitrogen application between early spring and early stem elongation (Zadok's 31-32) can further increase protein, but this is rarely economical. Newer hard red varieties are being developed with inherently increased protein. These varieties may not require increased nitrogen to achieve protein levels that maximize protein premiums. 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 using the nitrogen from 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 and 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 2,800 CHUs (see Figure 3-1, Crop Heat Units Available for Corn Production).

Since soils can vary greatly in their ability to supply nitrogen, the general recommendation found in Table 6-10, Nitrogen Requirements - 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. A recommendation based on a spring nitrate-nitrogen test should be considered as a guideline that is useful in formulating a nitrogen management program for spring barley (see Table 6-12, Nitrogen Recommendations for Spring Barley Based on Nitrate-Nitrogen Soil Tests).

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 the same depth (30 cm). 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 under the section Soil Sampling. See also Appendix L, Diagnostic Service.

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:

1. legumes or manure plowed down in the late summer or fall
2. 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 6-13, Yield Loss Associated with Inaccurate Nitrogen Application Patterns shows the yield loss associated with inaccurate spread patterns. A 1.48 t/ha (22 bu/ac) yield difference was found between the fully fertilized and under-fertilized strips in the field.

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Source: P. Johnson, OMAFRA

Based on two locations in Middlesex County, 1998, three replications at each location.

Twenty-eight per cent nitrogen applied with streamer nozzles gives excellent, uniform nitrogen application. Urea or ammonium nitrate (calcium ammonium nitrate) can also be applied using airflow technology, 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 are not recommended for nitrogen application on cereals, due to the inconsistency of their spread pattern. If spinners are employed, consider double spreading the field (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 as an overall broadcast treatment (using flood jet or tee-jet nozzles) to emerged cereal crops is NOT RECOMMENDED. Table 6-14, Yield Loss Associated With Leaf Burn From 28% Nitrogen Broadcast Treatment on Cereals, 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 102. U.A.N. 28% leaf burn. Applications of 28% U.A.N. fertilizer can burn leaves and reduce yields.

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Least significant difference = 7²

Adapted from Jim Kells, Michigan State University, 1994

¹Seven days after treatment
²Least significant difference: 5% level

Leaf Burn

Sometimes 28% leaf burn is credited with increasing tillering and a thicker, higher-yielding crop. In fact, visible leaf burn from a moving vehicle equates to at least 10% leaf damage. This level of damage would reduce the yield of an 5.71 t/ha (85 bu/ac) crop to only 5.38 t/ha (80 bu/ac). Twenty-eight per cent burn can be significant enough to kill underseeded red clover. Avoid leaf burn to increase 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.

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Phosphate and Potash

Phosphate and potash recommendations for cereals are given in Table 6-15, Phosphate and Potash Recommendations for Cereals Based on OMAFRA-Accredited Soil Tests.

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100 kg/ha = 90 lb/ac

¹Where manure is applied, reduce the fertilizer application according to the amount and quantity of manure (see the section Manure ). For spring barley in an area with less than 2,600 crop heat units, not manured and not following a legume sod, the nitrogen requirement is 70 kg/ha (see Table 6-10, Nitrogen Requirements - 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.
²A rating of "Excessive" may mean reduced yield or affected nutrient balance in crops and increased risk of nitrate movement into groundwater.
³Where manure is applied, reduce the fertilizer application according to the amount and quantity of manure see the section Manure) .
⁴A rating of "Excessive" 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.

For information on the use of these tables or if you do not have an OMAFRA-accredited soil test, refer to the section 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 2-30, Maximum Safe Rates of Nutrients.

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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 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.

A soil sample should be taken from the same area and at the same time as a plant sample.

For more information, see Table 6-16, Interpretation of Plant Analysis for Cereal Crops, as well as Appendix L, Diagnostic Service.

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Values apply to the top two leaves sampled at heading.

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

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Micronutrients

| Manganese | Copper | Boron | Zinc |

Manganese

Manganese deficiency frequently occurs when wheat, oats 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 oats, manganese deficiency appears as irregular oval grey spots on the leaves.

Plate 103. Manganese deficiency on oats 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. 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.

Plate 104. Manganese deficiency on winter wheat (pale-yellow intervenial strips on the leaf) occurs most frequently on high pH, sandy soils or on organic soils.

Correct the deficiency as soon as detected by spraying the foliage with 2 kg manganese/ha from manganese sulphate (8 kg manganese sulphate/ha) 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 insure winter survival.

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.

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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 the section on Micronutrient Fertilizers.

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Boron

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

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Zinc

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

Mixtures of herbicides and foliar fertilizers should not be applied to crop foliage unless recommended by competent authorities. Always consult the herbicide label.

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Updates on Cereals: Fertility

• Nitrate-nitrogen Soil Test and Spring Barley
• Nitrogen Requirements - Annual Field Crops
• Phosphorus Requirement Table - Field Crops
• Potassium Requirement Table - Field Crops
• Soil Acidity and Liming
• Lime Requirements to Correct Soil Acidity Based on Soil pH and Soil Buffer pH
• Magnesium Soil Test Ratings and Interpretations for All Crops
• Manganese Requirement Table and Zinc Requirement Table

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Related links...

• Cereals
• Soil Fertility & Crop Nutrition

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