Wheat Nutrition and Fertilizer Requirements: Nitrogen

 
 
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 Effect of nitrogen on growth | Nitrogen deficiency symptoms | Crop yield and protein response to increasing rates of applied nitrogen | Effect of split application vs. single applications of nitrogen on yield and protein content | Nitrogen supply | Factors influencing wheat response to nitrogen fertilizer | Nitrogen immobilization and losses | Nitrogen fertilizer placement and time of application

Adapted from the Canada Grains Council's Complete Guide to Wheat Management

Effect of Nitrogen on Wheat Growth

Nitrogen (N) is often the most deficient of all the plant nutrients. Wheat is very sensitive to insufficient nitrogen and very responsive to nitrogen fertilization.

The most important role of N in the plant is its presences in the structure of protein, the most important building substances from which the living material or protoplasm of every cell is made. In addition, nitrogen is also found in chlorophyll, the green colouring matter of leaves. Chlorophyll enables the plant to transfer energy from sunlight by photosynthesis. Therefore, the nitrogen supply to the plant will influence the amount of protein, protoplasm and chlorophyll formed. In turn, this influences cell size and leaf area, and photosynthetic activity.

Plants grown with an adequate supply of nitrogen make rapid and thrifty growth and are dark green in colour. Leaf and stem development is stimulated. Insufficient nitrogen results in lighter green colour, reduced tillering, and disturbance of normal cell growth division, and a decrease in rate, and extent of protein synthesis. Because of this crop yields may also be greatly reduced. Excessive nitrogen causes lush succulent growth, resulting in greatly increased danger of lodging, delayed maturity and greater susceptibility to diseases such as rusts, septoria and powdery mildew.

Plants contain more nitrogen than any other essential elements derived from the soil. Plants take up nitrogen from the time the roots begin to function until all uptake of nutrients ceases with maturity. However, the largest amounts are taken up during early stages of growth, held for later use and translocated within the plant where needed, for example, to the kernels from the leaves and stem during maturation.

On average a 40 bu/ac wheat crop at maturity will contain approximately 95 kg/ha (85 lb/ac) of nitrogen in the seed and straw.

Generally, 70% of the fertilizer nitrogen is contained in the seed, with the remaining 30% being in the straw (Table 1).
Table 1. Nitrogen used by wheat

Crop Yield
Crop Part
Nitrogen
Kg/ha
(lb/ac)
Wheat
2690 Kg/ha
(40 bu/ac)
seed
straw
total
67
28
95
60
25
85
Adapted from Simplot, 1986.

Nitrogen Deficiency Symptoms

The most easily observed symptom of nitrogen deficiency is the yellowing (chlorosis) of leaves due to a drop in chlorophyll content. This symptom is usually noticed first in the more mature leaves, and last in the upper actively growing leaves, because the N is translocated from older to new leaves to sustain growth. Thus, the older leaves will wither and result in poor plant growth and yield reduction. Generally growth is slowed, stunted and firing of the leaf tips and margins is evident.

Crop Yield and Protein Response to Increasing Rates of Applied Nitrogen

When soil available nitrogen is low, yield and protein content will be low. As more nitrogen becomes available, yield and protein rise concurrently. The yield responses to nitrogen are greater than protein responses up to certain levels of application. As nitrogen is applied beyond these levels the wheat plant will no longer use it to increase yield, but will be utilized to increase grain protein content. If high yields and protein are sought, high levels of nitrogen fertilizer must be applied. For Soft White Spring Wheat (SWSW) however, the optimum level of fertilizer application is up to the point of maximum yield response to nitrogen. Any excess application beyond this point will raise wheat protein significantly which is undesirable. It is thus possible with SWSW to achieve both a high yield and low protein. Proper timing of nitrogen fertilizer applications to high yielding varieties might be another means in attempting to achieve high yield and high protein.

A number of field experiments have shown that satisfactory and profitable yields of wheat can be achieved on fallow or continuously cropped land, with among other factors, adequate fertilizer and weed control practices. For example yields of cultivar Katepwa on continuously cropped sites were increased dramatically by increasing rates of nitrogen fertilizer up to 120 kg/ha (107 lb/ac) and remained relatively constant when more than 67 kg/ha (60 lb/ac) was added. On the fallow sites, yields are influenced by nitrogen fertilizer however the yield increases generally less dramatic than on continuously cropping. In the fallow year, microbial breakdown of soil organic matter releases significant amounts of plant available N resulting in lower N fertilizer requirements. Generally, continuously cropped land usually contains less nitrogen than fallowed land, therefore, it was not surprising that the yield response is greater on the non fallow sites than on the fallow sites.

These tables show spring wheat yield response to nitrogen fertilizer in areas of Alberta atlow, medium and high soil moisture levels.

2a, 2b, 2c = Brown
3a, 3b, 3c = Dark Brown
4a, 4b, 4c = Thin Black

When adequate moisture is available, yield responses have been obtained with up to 160 kg/ha (144 lb/ac) of applied nitrogen fertilizer. Yield increase tables for Hard Red Spring Wheat, Durum, Prairie Spring Wheats and Soft Wheat Spring Wheat under irrigated conditions have been developed for southern Alberta.

Based on Alberta research, it appears that with increasing rates of fertilizer nitrogen, wheat yields increase up to some optimal level. The optimal yield potential seems to have been increasing over the past number of years, due to improvement in new cultivars and new management practices. With the newly developed yield increase charts, farmers are now able to more clearly determine how much N fertilizer is necessary for optimum profitable yield, which comes from an economical analysis of maximum yield research data.

Protein response to increasing rates of nitrogen
The lack of adequate N can adversely affect wheat protein content which is a major component in the wheat grading system in Canada.

It is thought that wheat has a protein yield threshold, meaning that at some level of soil nitrogen, increased levels of nitrogen fertilizer will result in higher protein but will not increase yield. The level of originally available soil nitrogen appears to be very important. For example, on soils that originally contain very low levels of nitrogen, if inadequate nitrogen is applied, then the nitrogen will be utilized primarily for vegetative growth and perhaps not enough will be left for maximum protein production. Work in Saskatchewan suggested that it is possible to increase the grain protein content up to a maximum of 16%, while maintaining or increasing the yield, but beyond 16% protein, yield would be limited.

Nitrogen not only influences protein quantity but also influences protein quality. For instance, work at Lethbridge reported that nitrogen fertilization increased the proportion of glutamic acid, proline, methionine, cysteine, phenylalanine and tyrosine in the wheat grain. However, arginine, lysine, histidine, aspartic acid, threonine, glycine, valine and leucine were decreased.

Effect of Split Application vs. Single Applications of Nitrogen on Yield and Protein Content

It has not been easy to breed for high yield and high protein in Hard Red Spring Wheats (HRSW) because of the frequent negative correlations between protein and yield. As yield increases, protein decreases due to the dilution effect.

Limited research suggests that proper timing of nitrogen fertilizer applications to high yielding varieties can be successful as one of the means in attempting to achieve high yield and high protein.

Under dry conditions, sufficient moisture is not available to adequately move surface nitrogen that was applied at flowering into the soil for plant uptake. It is therefore not surprising that increased yields did not result when nitrogen was applied at flowering stage. However, foliar applied N at flowering may offer potential to increase grain protein content. Hopefully new research will be initiated in this area in 1997 in Alberta.

Work in southern Alberta with irrigated wheat, found that nitrogen was more efficient in increasing protein content when applied as a urea spray at the flowering stage than when applied to the soil before seeding. In addition, about the same protein content (18.8%) was obtained with a 5 kg N/ha (4 lb/ac) applied as urea spray, as with 100 kg N/ha (89 lb/ac) of granular fertilizer (34-0-0) applied to the soil.

In Manitoba, work with cultivars Katepwa and HY 320 found that split applications of nitrogen tended to increase percent protein in the grain. The protein percent difference was 0.2% between the single and split nitrogen applications at the 120 kg N/ha (107 lb/ac) rate for both cultivars. At a higher nitrogen rate ([160 kg N/ha][142 lb/ac]), the protein percent difference was 0.6% and 1.3% between the single and the three level split nitrogen applications for Katepwa and HY 320 cultivars respectively.

Although the effects of split application of nitrogen tend to be variable, the literature indicates that the later applied nitrogen tends to be more effective in increasing protein content of the grain. Information is still required regarding the optimum rates, times of application and sources of nitrogen for optimum protein and yields.

The guidelines for Maximum Economic Yield - Spring Wheat Production suggests split applications of nitrogen as follows: 40% pre-plant, 10% in starter, 25% at tillering (Zadoks Growth Stage 21-26) and 25% at stem elongation (Zadoks Growth stage 30-32). An additional nitrogen application of about 17-22 kg/ha (15-20 lb/ac) swollen boot (Zadoks Growth stage 45) can have significant effects on head fill and grain protein levels. However, this work has not been done in Alberta to confirm that these multi-split applications are effective to significantly increase wheat yield and/or grain protein. Further the economics of the price relationship of costs and returns needs to be examined closely before split N application for protein enhancement can be recommended.

Nitrogen Supply

There are a number of sources from which wheat plants can obtain nitrogen:
  1. Available nitrogen stored in the soil at planting.
  2. Nitrogen released from soil organic matter breakdown during the growing season.
  3. Nitrogen may be released from the breakdown of plant residue following a legume crop.
  4. Addition of inorganic commercial fertilizer or animal manure.
  5. Up to 20 kg/ha (18 lb/ac) of N during the growing season can be added from rainfall primarily from lightning storms.
Soil organic matter is the major reservoir for N and many other essential plant nutrients. The early farming systems commonly used across the prairie provinces involved summerfallowing and frequent tillage operations. As a result of these management practices, a large and rapid decline in soil organic matter occurred with correspondingly large losses in reserve supplies of important nutrients such as nitrogen. Many prairie soils have now lost much of their ability to supply large amounts of nitrogen to crops. Available nitrogen in the soil varies from field to field and from year to year. The release of nitrogen from soil organic matter is controlled by soil micro-organisms. During the decomposition of organic matter, soil micro-organisms convert organic nitrogen to the ammonium (NH4+) and nitrate (NO3-) forms of nitrogen, which plants utilize. As the changes are controlled by micro-organisms, they are largely affected by factors such as soil temperature, moisture content and pH.

Under cool, water logged or excessively low pH (acidic) conditions the microbial processes can be very slow.

Cultivation stimulates organic matter decomposition because mixing the soil improves aeration and supplies micro-organisms with fresh organic matter. Therefore, any switch to reduce mechanical disturbance of the soil may reduce organic matter depletion and potentially may even result in an increase of organic matter and total nitrogen levels .

Less nitrogen builds up on continuously cropped fields as compared to summerfallowed fields. However, on summerfallowed fields with excessive weeds or fields with low organic matter, there may not be sufficient nitrogen available for optimum wheat growth.

Factors Influencing Wheat Response to Nitrogen Fertilizer

The utilization of applied nitrogen fertilizer depends on the availability of soil nitrogen and the potential losses of applied nitrogen. Various other agronomic factors can cause a poor response to applied nitrogen including:

Wheat cultivar
Wheat varieties with higher yielding potential will respond to higher rates of applied nitrogen than those with lower yield potential, providing that other factors are not limiting.

Available soil nitrogen
Available soil nitrogen at planting time is one of the main factors that will influence crop response to fertilizer nitrogen. The nitrogen status of a field can be estimated from the previous cropping history, but is more accurately determined by a soil test, ( see Fertilizing Irrigated Grain and Oilseed Crops Agdex 100/541-1). Soils that have low plant available nitrogen will require more fertilizer nitrogen.

Delayed or late seeding
Late seeding usually results in a lower yield potential and therefore reduced response from nitrogen fertilizer due to moisture/heat relationships. Also, there is greater risk of crop loss from increased disease pressure, insects, frost and poor harvest conditions.

Weed competition
Weeds compete with wheat plants for moisture, nutrients and light. Applied nitrogen fertilizer may stimulate the growth of weed seedlings almost to the same extent as wheat. It is therefore important to control weeds in order to minimize the competition between weeds and wheat plants. Banding fertilizer or placing fertilizer with the seed makes it less accessible to weeds during the early growing season. However, if too much fertilizer is seed-placed injury to the seedling will reduce emergence resulting in higher weed competition.

Disease infestation
Well nourished, healthy plants provide a measure of resistance to many disease organisms . Inadequately nurtured wheat plants seem to be predisposed to certain diseases such as common root. Take-all root rot is reduced when wheat plants absorb ammonium nitrogen and is increased when the plants take up excessive amounts of nitrate nitrogen.

Soil moisture
In lower rainfall soil zones, soil moisture reserves must be considered when choosing fertilizer rates. On medium textured (loam) soils in the brown and dark brown soil zones, moist soil to a depth of 75 cm (30 in) and 68 cm (27 in) respectively is considered adequate for re-cropping stubble land. On fine textured (clay) soils in the brown and dark brown soil zones, moist soil to a depth of 55 cm (22 in) and 50 cm (20 in) respectively is considered adequate for re-cropping. When soil moisture exceeds these levels, higher rates of nitrogen will generally give economic returns. If the entire rooting zone (90-120 cm) (35-47 in) is moist, rates up to twice those normally recommended can be profitable. (See Tables 4,5, and 6)

The risk of crop damage or failure is higher on poorly drained or flood prone fields. Lower nitrogen fertilizer applications are advised on these fields if adequate drainage cannot be provided. Although well fertilized crops usually withstand more water, if water stands for more than 2 or 3 days causing saturated conditions, considerable crop damage or complete failure may result.

Coarse textured soils with water tables deeper than 1.2 to 1.8 m (4 to 6 ft) below the surface are often droughty. Yield potential to a large extent is restricted by lack of moisture. High rates of nitrogen fertilizers are generally not recommended in these soils.

Nitrogen Immobilization and Losses

Volatilization
Nitrogen from fertilizers containing ammonia or urea can be lost through volatilization as ammonia gas to the atmosphere. Ammonia volatilization increases with increasing soil pH, soil carbonate content and pH of the added fertilizer. These types of losses are far greater with urea (46-0-0) than with ammonium nitrate fertilizers (34-0-0) and ammonium sulphate (21-0-0-24).

Losses are greater in alkaline (high pH) soils than from acid soils and are higher under dry as compared to wet soil conditions.

The losses from sandy soils are usually higher than from heavier textured soils and are greater at high temperatures than at low temperatures. Greatest volatile losses can occur where there is just enough moisture to put fertilizer into solution, but not enough to move it in to the soil, followed by hot, dry windy conditions. Loss due to ammonia volatilization can be eliminated or greatly reduced if fertilizer is banded or well incorporated into the soil.

Ammonium fixation
The ammonium (NH4+) form of nitrogen can be temporarily retained by some clay minerals. Much of this nitrogen can be used by the plants at some time during the growing season. Ammonium fixation is generally not considered to be a major factor by which fertilizer nitrogen availability is reduced.

Erosion
Nitrogen fertilizer can be lost in runoff waters and through soil erosion caused by either wind or water. Runoff losses of applied fertilizers can be reduced by banding fertilizer into the soil. Cultural methods to control wind and water erosion should be used to minimize N losses. Generally, it is not advisable to apply fertilizer to frozen soils.

Leaching
Leaching refers to the movement of nitrate nitrogen in the soil solution through and out of the root zone. When leaching occurs, nitrogen is lost from the root zone, thereby reducing the utilization of nitrogen by wheat plants. Losses of this nature are minimal during winter and the growing season. However, nitrate leaching can occur during late fall or early spring, in particularly sandy soils or irrigated soils. Leaching can also be a significant problem on summerfallow land. Generally, nitrate leaching is a less serious concern in clay soils. Leaching losses of nitrogen applied in the spring close to the time of seeding are minimal on most soils. Leaching losses are also reduced by using ammonium fertilizers banded into the soil.

Immobilization
Immobilization refers to the conversion of plant available nitrogen to organic nitrogen by soil micro-organisms. This nitrogen is not lost but is tied up temporarily and is released slowly for crop use through mineralization. It is important to remember that soil microbes compete with growing crops for applied nitrogen fertilizer, which may result in reduced crop growth.

Immobilization of ammonium nitrogen is slightly greater than immobilization of nitrate-nitrogen. Considerable amounts of inorganic nitrogen is removed by immobilization (20 to 40%) from the available form. Higher nitrogen immobilization in surface soil under minimum and zero till management may reduce available nitrogen to crops in the early part of the growing season. Banding of nitrogen rather than broadcast incorporation is effective to decrease nitrogen losses by immobilization.

Denitrification
This process results in the reduction of nitrate-nitrogen to nitrogenous gases such as nitrogen (N2) and nitrous oxide, which are lost to the atmosphere. Considerable nitrate-nitrogen may be lost by denitrification when soils are temporarily wet (early spring or after heavy rainfall). This is because the micro-organisms that convert nitrate to nitrogenous gas work optimally under high moisture or saturated soil conditions.

Denitrification: NO3- ---->NO2----->N2O
|
|
NO
N2
Areas of the province, such as west central Alberta, that tend to be saturated for extended periods in the spring are the most prone to significant denitrification losses. For this reason, nitrogen fertilizer should not be applied in the fall to areas that are subject to saturated soil conditions in the spring or to low lying land subject to flooding. Because of possible denitrification losses, it is generally recommended that fall applied nitrogen be banded in the ammonium form and applied as late as possible when the soil is cold, so that the nitrogen will remain in the ammonium form. Denitrification losses do not occur as long as the fertilizer nitrogen is present in the ammonium form. On summerfallow fields, the available nitrogen is present in the nitrate form, and is, therefore quite vulnerable to losses under excess moisture conditions.

Some recent studies in Saskatchewan have shown that there is a greater potential for losses of nitrogen through denitrification under minimum and zero-till cropping conditions than when conventional tillage is practised because soil is moister.

Nitrogen Fertilizer Placement and Time of Application

The method of placement and time of application can have significant effect on the efficiency of nitrogen fertilizer by increasing yield and/or protein. Methods of application include:
  1. Drilling in with the seed
  2. Sideband placement
  3. Banding into soil prior to seeding
  4. Broadcast and incorporated into the soil
  5. Broadcast without incorporation
  6. Pocket or nest fertilizer
  7. Foliar application
There are a number of factors which will influence the magnitude of wheat response to N fertilizer and its placement. These include:
  1. Rate of fertilizer - the higher the rate, the less impact placement will have.
  2. Soil test levels - the higher the soil test level, the less impact placement will have.
  3. The higher the rainfall, the less impact placement has.
  4. Ammonium nitrate is less sensitive than urea based fertilizer to placement. Anhydrous ammonia (NH3) has to be banded.
  5. Crop rotation - legumes in rotation with cereals can reduce the impact of placement.
Drilled with the seed
Drilling N with the seed is one of the most effective means of adding nitrogen fertilizer. The safe rates of N fertilizer that can be seed-placed is provided in Table 5. If seedbed moisture conditions are favourable, up to 45 kg N/ha (40 lb/ac) can be applied with the seed. More than 20 kg N/ha (18 lb/ac) when applied with a double disc drill can cause seedling damage and reduce yield increases. Higher rates of urea can be used with seeding equipment which spread the seed and fertilizer in a wider band. Many air seeders are capable of creating a band 4-8 inches wide.

Table 5. Safe rates of seed-placed fertilizer
Crop
Soil texture
Seedbed
soil moisture
Phosphate
*Double disc or
narrow hoe drill
**Pneumatic seeder
50% spread
Urea
Ammonium
nitrate
Urea
Ammonium
nitrate
lb/ac
lb/ac of Nitrogen (N)
Wheat
Barley
Oats
Medium to
fine
Good
Poor
70
70
30
20
45
30
45
30
65
45
Coarse
Good
Poor
70
70
20
15
30
20
35
25
55
35
Small seeded
crops
All textures
Good
Poor
10-20
0-10
10
0
20
10
20
10
35
25

Sideband placement
Sideband placement of N is equal in effectiveness to N drilled with the seed, however, it has the advantage that higher amounts can be used. Attachments for side banding are only available on some types air seeders and direct seeding equipment. Therefore, this type of N placement has limitations to fertilize spring wheat. A form of side banding which has been developed in recent years is the paired row system, where fertilizer is placed between two seed rows. Certain hoe drills and air seeders can be adapted for this purpose. An advantage of side banding is that fertilizer is more selectively available, favouring the crop more than the weeds.

Banded into soil prior to seeding
Banding N into soil, prior to seeding is about equal in effectiveness to side banding or seed placement. Nitrogen fertilizer is applied in a band behind a shank or disc at depths of 7.5 to 10 cm (3-4 in). Generally, seeding can take place immediately after fertilizer application. In the past, it was recommended that seeding be delayed for two days after banding anhydrous ammonia (NH3). However, in many soils as long as the NH3 is placed 5- 7.5 cm ( 2-3 inches) away from the seed, NH3 can be applied at the time of seeding. Seed damage from NH3 is most likely to occur under dry conditions on sandy soils when there is insufficient separation from the seed. Placement of fertilizer nitrogen should be deeper in sandy soils than in loams or heavy textured soils. Narrow band spacing 25 to 30 cm (10-12 in) is better than wider band spacing particularly under low moisture conditions. Research has shown that with low soil moisture, in cool spring conditions, narrower spacings are more effective in minimizing temporary or season long N deficiency.

Broadcast and incorporated into the soil
Generally, this method does not result in a yield and/or protein increases as large as those obtained by band placement. To minimize volatilization losses, urea and liquid or dry fertilizer containing urea should be well incorporated into the soil. Shallow incorporation of these fertilizers may result in ammonia volatilization. In cases where incorporation is not desirable due to moisture or soil conservation reasons, losses are reduced by applying fertilizer at a soil temperature of less than 5C or by applying ammonium nitrate fertilizer which is not subject to volatilization losses.

Broadcast without incorporation
This method is the least efficient use of fertilizer nitrogen. When urea is used, ammonia volatilization losses can be appreciable resulting in lower yield and/or protein content than obtained when the fertilizer nitrogen is incorporated or banded. The use of ammonium nitrate is the preferred source of nitrogen for surface broadcast application due to its low volatilization potential.

"Pocket"or "nest" fertilization
In a 3 year study in north-central and central Alberta, researchers found that fall application of urea by nest placement using 2 g (.1 oz) urea pellets placed in the soil in at 45 cm (18 in) spaced rows at 40 cm (16 in) intervals, brought yield increases to about 90% of those achieved with spring applied nitrogen. This new technology has not yet been developed commercially in western Canada, but may have potential in the future. As with wide bands, widely spaced nests may limit availability of fertilizer to crop plants especially in dry or cool soil conditions.

Foliar nitrogen application
Nitrogen in liquid form has been foliar applied at heading to the soft dough stage with some success to increase wheat protein content. Applications are generally in the range of 7 to 15 kg/ha (6 to 14 lb/ac) of N. Rates above 20 kg/ha can potentially cause some tissue burning resulting in crop injury. A new research project to examine the viability to this method of application at different growth stages of wheat may be initiated in 1997.

Time of application
The relative efficiency of nitrogen fertilizers as affected by time of application and method of placement varies greatly from year to year due to environmental conditions.

Generally, nitrogen applied in the spring at seeding is usually more effective for increasing wheat yields and/or protein content than adding nitrogen in the fall. However, there are exceptions. In dry areas, where seedbed quality and moisture conservation are a major concern, spring applications have the disadvantage of deeply working the soil and resulting in a loss of soil moisture. Alberta research has shown the dry areas, such as the brown and dark brown soil zones, there is little difference between fall and spring applications with anhydrous ammonia. Studies with ammonium nitrate (34-0-0) have shown that losses of nitrate through denitrification and immobilization in decomposing crop residues are appreciable in soils of northern Alberta. Therefore, it is recommended that the practice of fall application of ammonium nitrate should be discontinued in favour of fall applied urea or NH3 or applying N shortly before seeding in spring.

Saskatchewan research has shown that in years of favourable moisture, yields were generally greater for spring applied than fall applied urea nitrogen, and for deep banded than for broadcast nitrogen. In dry years, however, wheat yields did not respond to nitrogen fertilizer or to the method of fertilizer management used. The overall relative yield ratings for spring band, fall band, spring broadcast and fall broadcast were 100, 95, 94, and 91% respectively. In dry years, fall broadcasting of urea provided the greatest profit due largely to the lower costs for broadcasting compared to banding fertilizer. In years with favourable moisture, there was generally little difference in net returns among the fertilizer management systems. Applying fertilizer in the fall can often be advantageous as it reduces labour requirements and can increases timeliness for spring operations. Generally, fertilizer prices are often lower in the fall, making it economical to consider fall fertilizer application.
With developments in new direct seeding equipment, which allows one pass seeding and fertilizing, this will help to minimize the time factors with spring fertilization.

Spring and fall broadcast and incorporated nitrogen fertilizers have similar nitrogen efficiencies under low rainfall conditions of the brown and dark brown soils (Table 6). Fall or spring banded N have relatively similar efficiency and both are better than broadcast and incorporated N which is the least efficient.

Under dry conditions, which are most frequently encountered in the brown, dark brown and some degraded soils of the Peace River region, research has shown that fall broadcast N can be 75 - 100% as effective as urea nitrogen broadcast in the spring of the year and fall application of nitrogen by banding is 90 - 105% as effective as spring banding. If the soil is very dry in the spring, the tillage associated with deep banding could desiccate the soil further, making it significantly less effective than fall banding, as a result of soil moisture losses.

In wetter areas of the province, broadcast incorporated nitrogen is 50 - 75% as effective as spring broadcast nitrogen under these same conditions. Fall banded nitrogen is 85 - 95% as effective as spring banding application.

When the soil is very wet, and even saturated for several weeks in the spring, fall broadcast incorporated nitrogen can be 20% or less, as effective as spring broadcast nitrogen. Under these conditions, fall banded nitrogen can be 75 - 85% as effective as spring banded nitrogen.

Table 6. Relative effectiveness of N fertilizers
Method
Low Rainfall
(Brown and Dark Brown soils)
Medium rainfall
(Thin Black and some Black soils)
High Rainfall
(Gray Black and Gray soils)
Spring broadcast
and incorporated
100
100
100
Spring banded
115
110
110
Fall broadcast
and incorporated*
100
85
80
Fall banded*
115
95
85
*In September or early October the relative value is less than shown, whereas in late fall the relative value is greater than shown.
Source, Alberta Agriculture, Agdex 541-1, 1984.

Predicted Crop Yield (bu/ac)

Crop=HRS | Soil Test Area=Brown | Moisture=Low
Rate of Nitrogen Fertilizer (lb/ac)
0102030405060708090100110120130140150
Soil Test Nitrogen
(lb/ac/2 ft/Depth)
9.214.517.820.121.823.224.224.224.224.224.224.224.224.224.224.2
20
14.517.820.121.823.224.224.224.224.224.224.224.224.224.224.224.2
30
17.820.121.823.224.224.224.224.224.224.224.224.224.224.224.224.2
40
20.121.823.224.224.224.224.224.224.224.224.224.224.224.224.224.2
50
21.823.224.224.224.224.224.224.224.224.224.224.224.224.224.224.2
60
23.224.224.224.224.224.224.224.224.224.224.224.224.224.224.224.2
70
24.224.224.224.224.224.224.224.224.224.224.224.224.224.224.224.2
80
24.224.224.224.224.224.224.224.224.224.224.224.224.224.224.224.2
90
24.224.224.224.224.224.224.224.224.224.224.224.224.224.224.224.2
100
24.224.224.224.224.224.224.224.224.224.224.224.224.224.224.224.2
110
24.224.224.224.224.224.224.224.224.224.224.224.224.224.224.224.2
120
24.224.224.224.224.224.224.224.224.224.224.224.224.224.224.224.2
130
24.224.224.224.224.224.224.224.224.224.224.224.224.224.224.224.2
140
24.224.224.224.224.224.224.224.224.224.224.224.224.224.224.224.2
150
24.224.224.224.224.224.224.224.224.224.224.224.224.224.224.224.2


Predicted Crop Yield (bu/ac)

Crop=HRS | Soil Test Area=Brown | Moisture=Medium
Rate of Nitrogen Fertilizer (lb/ac)
0102030405060708090100110120130140150
Soil Test Nitrogen
(lb/ac/2ft Depth)
10
10.116.621.124.527.129.130.832.233.333.333.333.333.333.333.333.3
20
16.621.124.527.129.130.832.233.333.333.333.333.333.333.333.333.3
30
21.124.527.129.130.832.233.333.333.333.333.333.333.333.333.333.3
40
24.527.129.130.832.233.333.333.333.333.333.333.333.333.333.333.3
50
27.129.130.832.233.333.333.333.333.333.333.333.333.333.333.333.3
60
29.130.832.233.333.333.333.333.333.333.333.333.333.333.333.333.3
70
30.832.233.333.333.333.333.333.333.333.333.333.333.333.333.333.3
80
32.233.333.333.333.333.333.333.333.333.333.333.333.333.333.333.3
90
33.333.333.333.333.333.333.333.333.333.333.333.333.333.333.333.3
100
33.333.333.333.333.333.333.333.333.333.333.333.333.333.333.333.3
110
33.333.333.333.333.333.333.333.333.333.333.333.333.333.333.333.3
120
33.333.333.333.333.333.333.333.333.333.333.333.333.333.333.333.3
130
33.333.333.333.333.333.333.333.333.333.333.333.333.333.333.333.3
140
33.333.333.333.333.333.333.333.333.333.333.333.333.333.333.333.3
150
33.333.333.333.333.333.333.333.333.333.333.333.333.333.333.333.3


Predicted Crop Yield (bu/ac)

Crop=Hrs | Soil Test Area=Brown | Moisture=High
Rate of Nitrogen Fertilizer Applied (lb/ac)
0102030405060708090100110120130140150
Soil Test Nitrogen
(lb/ac/2ft Depth)
10
11.019.325.831.035.338.841.844.446.748.650.451.953.354.555.656.7
20
19.325.831.035.338.841.844.446.748.650.451.953.354.555.656.756.7
30
25.831.035.338.841.844.446.748.650.451.953.354.555.656.756.756.7
40
31.035.338.841.844.446.748.650.451.953.354.555.656.756.756.756.7
50
35.338.841.844.446.748.650.451.953.354.555.656.756.756.756.756.7
60
38.841.844.446.748.650.451.953.354.555.656.756.756.756.756.756.7
70
41.844.446.748.650.451.953.354.555.656.756.756.756.756.756.756.7
80
44.446.748.650.451.953.354.555.656.756.756.756.756.756.756.756.7
90
46.748.650.451.953.354.555.656.756.756.756.756.756.756.756.756.7
100
48.650.451.953.354.555.656.756.756.756.756.756.756.756.756.756.7
110
50.451.953.354.555.656.756.756.756.756.756.756.756.756.756.756.7
120
51.953.354.555.656.756.756.756.756.756.756.756.756.756.756.756.7
130
53.354.555.656.756.756.756.756.756.756.756.756.756.756.756.756.7
140
54.555.656.756.756.756.756.756.756.756.756.756.756.756.756.756.7
150
55.656.756.756.756.756.756.756.756.756.756.756.756.756.756.756.7


Predicted Crop Yield (bu/ac)

Crop=HRS Wheat | Soil Test Area=Dark Brown | Moisture=Low
Rate of Nitrogen Fertilizer Applied (lb/ac)
0102030405060708090100110120130140150
Soil Test Nitrogen
(lb/ac/2ft Depth)
10
9.715.318.921.423.324.725.925.925.925.925.925.925.925.925.925.9
20
15.318.921.423.324.725.925.925.925.925.925.925.925.925.925.925.9
30
18.921.423.324.725.925.925.925.925.925.925.925.925.925.925.925.9
40
21.423.324.725.925.925.925.925.925.925.925.925.925.925.925.925.9
50
23.324.725.925.925.925.925.925.925.925.925.925.925.925.925.925.9
60
24.725.925.925.925.925.925.925.925.925.925.925.925.925.925.925.9
70
25.925.925.925.925.925.925.925.925.925.925.925.925.925.925.925.9
80
25.925.925.925.925.925.925.925.925.925.925.925.925.925.925.925.9
90
25.925.925.925.925.925.925.925.925.925.925.925.925.925.925.925.9
100
25.925.925.925.925.925.925.925.925.925.925.925.925.925.925.925.9
110
25.925.925.925.925.925.925.925.925.925.925.925.925.925.925.925.9
120
25.925.925.925.925.925.925.925.925.925.925.925.925.925.925.925.9
130
25.925.925.925.925.925.925.925.925.925.925.925.925.925.925.925.9
140
25.925.925.925.925.925.925.925.925.925.925.925.925.925.925.925.9
150
25.925.925.925.925.925.925.925.925.925.925.925.925.925.925.925.9

Predicted Crop Yield (bu/ac)

Crop=HRS Wheat | Soil Test Area=Dark Brown | Moisture=Medium
Rate of Nitrogen Fertilizer Applied (lb/ac)
0102030405060708090100110120130140150
Soil Test Nitrogen
(lb/ac/2ft Depth)
10
10.617.522.426.028.831.132.934.435.736.836.836.836.836.836.836.8
20
17.522.426.028.831.132.934.435.736.836.836.836.836.836.836.836.8
30
22.426.028.831.132.934.435.736.836.836.836.836.836.836.836.836.8
40
26.028.831.132.934.435.736.836.836.836.836.836.836.836.836.836.8
50
28.831.132.934.435.736.836.836.836.836.836.836.836.836.836.836.8
60
31.132.934.435.736.836.836.836.836.836.836.836.836.836.836.836.8
70
32.934.435.736.836.836.836.836.836.836.836.836.836.836.836.836.8
80
34.435.736.836.836.836.836.836.836.836.836.836.836.836.836.836.8
90
35.736.836.836.836.836.836.836.836.836.836.836.836.836.836.836.8
100
36.836.836.836.836.836.836.836.836.836.836.836.836.836.836.836.8
110
36.836.836.836.836.836.836.836.836.836.836.836.836.836.836.836.8
120
36.836.836.836.836.836.836.836.836.836.836.836.836.836.836.836.8
130
36.836.836.836.836.836.836.836.836.836.836.836.836.836.836.836.8
140
36.836.836.836.836.836.836.836.836.836.836.836.836.836.836.836.8
150
36.836.836.836.836.836.836.836.836.836.836.836.836.836.836.836.8

Predicted Crop Yield (bu/ac)

Crop=HRS Wheat | Soil Test Area=Dark Brown | Moisture=High
Rate of Nitrogen Fertilizer Applied (lb/ac)
0102030405060708090100110120130140150
Soil Test Nitrogen
(lb/ac/2ft Depth)
10
11.520.327.332.937.541.344.647.549.952.154.055.757.258.659.961.0
20
20.327.332.937.541.344.647.549.952.154.055.757.258.659.961.062.0
30
27.332.937.541.344.647.549.952.154.055.757.258.659.961.062.062.0
40
32.937.541.344.647.549.952.154.055.757.258.659.961.062.062.062.0
50
37.541.344.647.549.952.154.055.757.258.659.961.062.062.062.062.0
60
41.344.647.549.952.154.055.757.258.659.961.062.062.062.062.062.0
70
44.647.549.952.154.055.757.258.659.961.062.062.062.062.062.062.0
80
47.549.952.154.055.757.258.659.961.062.062.062.062.062.062.062.0
90
49.952.154.055.757.258.659.961.062.062.062.062.062.062.062.062.0
100
52.154.055.757.258.659.961.062.062.062.062.062.062.062.062.062.0
110
54.055.757.258.659.961.062.062.062.062.062.062.062.062.062.062.0
120
55.757.258.659.961.062.062.062.062.062.062.062.062.062.062.062.0
130
57.258.659.961.062.062.062.062.062.062.062.062.062.062.062.062.0
140
58.659.961.062.062.062.062.062.062.062.062.062.062.062.062.062.0
150
59.961.062.062.062.062.062.062.062.062.062.062.062.062.062.062.0


Predicted Crop Yield (bu/ac)

Crop=HRS Wheat | Soil Test Area=Thin Black & Black | Moisture=Low
Rate of Nitrogen Fertilizer Applied (lb/ac)
0102030405060708090100110120130140150
Soil Test Nitrogen
(lb/ac/2ft Depth)
10
10.717.321.825.127.629.531.132.433.533.533.533.533.533.533.533.5
20
17.321.825.127.629.531.132.433.533.533.533.533.533.533.533.533.5
30
21.825.127.629.531.132.433.533.533.533.533.533.533.533.533.533.5
40
25.127.629.531.132.433.533.533.533.533.533.533.533.533.533.533.5
50
27.629.531.132.433.533.533.533.533.533.533.533.533.533.533.533.5
60
29.531.132.433.533.533.533.533.533.533.533.533.533.533.533.533.5
70
31.132.433.533.533.533.533.533.533.533.533.533.533.533.533.533.5
80
32.433.533.533.533.533.533.533.533.533.533.533.533.533.533.533.5
90
33.533.533.533.533.533.533.533.533.533.533.533.533.533.533.533.5
100
33.533.533.533.533.533.533.533.533.533.533.533.533.533.533.533.5
110
33.533.533.533.533.533.533.533.533.533.533.533.533.533.533.533.5
120
33.533.533.533.533.533.533.533.533.533.533.533.533.533.533.533.5
130
33.533.533.533.533.533.533.533.533.533.533.533.533.533.533.533.5
140
33.533.533.533.533.533.533.533.533.533.533.533.533.533.533.533.5
150
33.533.533.533.533.533.533.533.533.533.533.533.533.533.533.533.5


Predicted Crop Yield (bu/ac)

Crop=HRS Wheat | Soil Test Area=Thin Black & Black | Moisture=Medium
Rate of Nitrogen Fertilizer Applied (lb/ac)
0102030405060708090100110120130140150
Soil Test Nitrogen
(lb/ac/2ft Depth)
10
11.519.525.430.033.636.539.041.042.844.345.646.847.847.847.847.8
20
19.525.430.033.636.539.041.042.844.345.646.847.847.847.847.847.8
30
25.430.033.636.539.041.042.844.345.646.847.847.847.847.847.847.8
40
30.033.636.539.041.042.844.345.646.847.847.847.847.847.847.847.8
50
33.636.539.041.042.844.345.646.847.847.847.847.847.847.847.847.8
60
36.539.041.042.844.345.646.847.847.847.847.847.847.847.847.847.8
70
39.041.042.844.345.646.847.847.847.847.847.847.847.847.847.847.8
80
41.042.844.345.646.847.847.847.847.847.847.847.847.847.847.847.8
90
42.844.345.646.847.847.847.847.847.847.847.847.847.847.847.847.8
100
44.345.646.847.847.847.847.847.847.847.847.847.847.847.847.847.8
110
45.646.847.847.847.847.847.847.847.847.847.847.847.847.847.847.8
120
46.847.847.847.847.847.847.847.847.847.847.847.847.847.847.847.8
130
47.847.847.847.847.847.847.847.847.847.847.847.847.847.847.847.8
140
47.847.847.847.847.847.847.847.847.847.847.847.847.847.847.847.8
150
47.847.847.847.847.847.847.847.847.847.847.847.847.847.847.847.8


Predicted Crop Yield (bu/ac)

Crop=HRS Wheat | Soil Test Area=Thin Black & Black | Moisture=High
Rate of Nitrogen Fertilizer Applied (lb/ac)
0102030405060708090100110120130140150
Soil Test Nitrogen
(lb/ac/2ft Depth)
10
12.322.230.236.842.547.351.455.158.361.163.765.968.069.971.673.2
20
22.230.236.842.547.351.455.158.361.163.765.968.069.971.673.274.6
30
30.236.842.547.351.455.158.361.163.765.968.069.971.673.274.676.0
40
36.842.547.351.455.158.361.163.765.968.069.971.673.274.676.077.2
50
42.547.351.455.158.361.163.765.968.069.971.673.274.676.077.278.3
60
47.351.455.158.361.163.765.968.069.971.673.274.676.077.278.379.4
70
51.455.158.361.163.765.968.069.971.673.274.676.077.278.379.479.4
80
55.158.361.163.765.968.069.971.673.274.676.077.278.379.479.479.4
90
58.361.163.765.968.069.971.673.274.676.077.278.379.479.479.479.4
100
61.163.765.968.069.971.673.274.676.077.278.379.479.479.479.479.4
110
63.765.968.069.971.673.274.676.077.278.379.479.479.479.479.479.4
120
65.968.069.971.673.274.676.077.278.379.479.479.479.479.479.479.4
130
68.069.971.673.274.676.077.278.379.479.479.479.479.479.479.479.4
140
69.969.971.673.274.676.077.278.379.479.479.479.479.479.479.479.4
150
69.971.673.274.676.077.278.379.479.479.479.479.479.479.479.479.4
 
 
 
 

Other Documents in the Series

 
  Wheat Nutrition and Fertilizer Requirements
Wheat Nutrition and Fertilizer Requirements: Nitrogen - Current Document
Wheat Nutrition and Fertilizer Requirements: Potassium
Wheat Nutrition and Fertilizer Requirements: Sulphur
Wheat Nutrition and Fertilizer Requirements: Micronutrients
 
 
 
 
For more information about the content of this document, contact Ross McKenzie.
This document is maintained by Judy Chow.
This information published to the web on June 20, 2001.
Last Reviewed/Revised on June 1, 2010.