| | Introduction | Nitrogen fertilizer | Phosphate fertilizer | Potassium fertilizer | Sulphur fertilizer
.
Introduction
The Fertilizer Act requires fertilizers be labelled according to their guaranteed analysis as per cent by weight of nitrogen (N), phosphate (P2O5, and potash (K2O). For example, 100 lb of 11-51-0 contains 11 lb of nitrogen (N), 51 lb of phosphate (P2O5, and 0 lb of potash (K2O). Fertilizer should be purchased on the basis of the price per lb or kg of nutrient not price per tonne of material. For example:
| 1) | if urea (46-0-0) costs $265.00/tonne, the cost per kilogram or pound of nitrogen (N) is:
1000 kg x 46 = 460 kg or 1014 lb
..............100
$265.00 = $0.58/kg or $0.26/lb of N
.460 kg
(1 tonne = 1000 kg and 1 kg = 2.2 lb) |
.
2) | .
if ammonium nitrate (34-0-0) costs $220/tonne the cost per kg or lb of nitrogen (N) is:
1000 kg x 34 = 340 kg or 749 lb
..............100
$220.00 = $0.65/kg or $0.29/lb of N
.340 kg |
In this example, urea cost more per tonne ($265.00) than ammonium nitrate ($220.00) but cost less per unit of N ($0.26/lb vs. $0.29).
When determining the amount of fertilizer required to supply a given rate of nutrient, refer to Table 7.
Nitrogen Fertilizer
Placement
Nitrogen fertilizers are very soluble and move readily in moist soil. Placement with or very near the seed is not necessary to ensure effective utilization. Placement options that can be considered include:
- broadcast,
- pre-plant band,
- side-band or mid-row band at planting, and
- seed row placement.
The relative efficiencies of the various methods depends on many factors. Broadcast application may be less effective than banded or seed row application under some conditions (see Table 6). Fertilizer placed in the seed row can delay or severely reduce crop emergence. The maximum rate that can be safely placed in the seed row depends on:
- crop type,
- soil moisture,
- soil type (clay and organic matter content),
- type of fertilizer,
- row spacing, and
- spread of seed and fertilizer (type of opener).
Guidelines for approximate safe rates of seed row nitrogen are shown in Tables 4 and 5. (Note: all rates are in lb/ac of N. To calculate the rate of urea divide by 0.46).
Banding
Banding fertilizer (8-15 cm deep) has become a common method of applying nitrogen fertilizers. Under conditions of low rainfall during the early growing season, deeper placement overcomes the problem of nitrogen being stranded in dry surface soil. Under wet soil conditions that can occur in early spring (during and just after spring thaw), fall applied nitrogen fertilizer can be lost by a process called denitrification. Late fall banding of an ammonium form of nitrogen (e.g., 82-0-0 or 46-0-0) will reduce losses.
Time of application
Fall is often an opportune time to apply fertilizers because of the availability of time and price discounts. However, excessively wet conditions in early spring that sometimes occur on fine textured and poorly drained soils in central and northern Alberta can cause significant losses of fall applied nitrogen. Early fall (before mid-October) broadcast applications are most subject to loss. Late fall banded applications of an ammonium form of nitrogen are less subject to loss. Table 6 shows the relative efficiency of fall and spring broadcast and banded applications under various conditions.
Top dressing of nitrogen on cereals after emergence is not generally recommended but it can be effective up to the shot-blade stage if adequate rainfall is received after application.
Table 4. Maximum rates of nitrogen a (as urea-46-0-0) that can be safely placed in the seed row with cereal grains (wheat, barley and oats).
 | Width of spread of fertilizer in the row b |
1 inch | 2 inch | 3 inch | 4 inch |
(Disc or knife) | (Spoon or hoe) | (Sweep) | (Sweep) |
Row spacing | 6" | 9" | 12" | 6" | 9" | 12" | 6" | 9" | 12" | 6" | 9" | 12" |
Seed bed utilization (SBU) c | 17% | 11% | 8% | 33% | 22% | 17% | 50% | 33% | 25% | 67% | 44% | 33% |
| Pounds of N per acre |
Light soil (sandy loam) | 20 | 15 | 10 | 30 | 25 | 20 | 40 | 30 | 20 | 50 | 40 | 30 |
Medium soil (loam to clay loam) | 30 | 25 | 20 | 40 | 35 | 30 | 50 | 40 | 35 | 60 | 50 | 40 |
Heavy soil (clay to heavy clay) | 40 | 35 | 30 | 50 | 40 | 35 | 60 | 50 | 40 | 70 | 60 | 50 |
Table 5. Maximum rates of nitrogen a (as urea-46-0-0) that can be safely placed in the seed row with canola and flax.
| Width of spread of fertilizer in the row b |
1 inch | 2 inch | 3 inch | 4 inch |
(Disc or knife) | (Spoon or hoe) | (Sweep) | (Sweep) |
Row spacing | 6" | 9" | 12" | 6" | 9" | 12" | 6" | 9" | 12" | 6" | 9" | 12" |
Seed bed utilization (SBU)c | 17% | 11% | 8% | 33% | 22% | 17% | 50% | 33% | 25% | 67% | 44% | 33% |
| Pounds of N per acre |
Light soil (sandy loam) | 10 | 5 | 0 | 20 | 15 | 10 | 30 | 10 | 15 | 40 | 25 | 20 |
Medium soil (loam to clay loam) | 15 | 10 | 5 | 30 | 20 | 15 | 40 | 30 | 20 | 50 | 35 | 30 |
Heavy soil (clay to heavy clay) | 20 | 15 | 10 | 40 | 30 | 20 | 50 | 40 | 30 | 60 | 45 | 40 |
a The N rates in these tables are in addition to the N in safe rates of seed row phosphate fertilizer (monammonium phosphate).
b The width of spread of fertilizer and seed depends on the type of opener, soil type and moisture content, air flow, etc. Some openers give less than 1" spread(e.g., double disc).
c SBU (Seed bed Utilization) is the width of spread of fertilizer and seed relative to the row spacing. For example a 3" spread with a 6" row spacing is 50% SBU (3/6 x 100 = 50%). If the same rate of fertilizer is applied with a 3" spread and a 12" row spacing, the concentration of fertilizer in the seed row is doubled (3/12 x 100 = 25% SBU). Some openers spread seed and fertilizer vertically. SBU does not take vertical spread into account. A uniform seeding depth (minimum vertical spread) is conducive to even germination and emergence.
Table 6. The relative effectiveness of methods and time of nitrogen application for increasing crop yield.
| Soil-climatic categories |
| Method and time of application | 1 | 2 | 3 | 4 |
(dry) a | (medium) | (wet) b | (Irrigated) |
| Spring broadcast and incorporated | 100 | 100 | 100 | 100 |
| Spring banded | 120 | 110 | 105 | 110 |
| Fall broadcast and incorporated a | 90 | 75 | 65 | 95 |
| Fall banded | 120 | 110 | 85 | 110 |
a Although spring and fall banded nitrogen were equally effective in research trials, fall banding may be more practical under farm conditions. The extra tillage associated with spring banding may dry the seedbed and reduce yields.
b In research trials conducted in the higher rainfall areas, spring broadcast nitrogen was well incorporated and seeding and packing completed within a short period of time. Under farm conditions, shallow incorporation or loss of seedbed moisture resulting from deeper incorporation may cause spring broadcasting to be somewhat less effective than shown here.
Other factors that affect the 'safe' rate of seed row N
Soil moisture
The 'safe' rates of seed row N given in Tables 5 and 6 are for good to excellent seedbed moisture. If seedbed moisture is below the good to excellent range, the `safe' rates should be reduced by 25-50 per cent. In addition to soil moisture conditions at planting, rapid drying of the seedbed after planting can result in fertilizer injury. Packing and residue cover will slow moisture loss.
Field variability
Soils on rolling topography often have dry, eroded hill tops. The combined effects of low soil moisture, low organic matter and the presents of free lime make these areas very sensitive to crop injury from seed row N. The `safe' rate of seed row N on these areas is often less than one-half that of the remainder of the field. The `safe' rate for a field will be governed by the `safe' rate for the most sensitive areas.
Nitrogen source
Tables 5 and 6 give `safe' rates of seed row N for urea (46-0-0). The `safe' rates of seed row N for cereal grains is about 50 per cent higher if ammonium nitrate (34-0-0) is used in place of urea (assuming that seedbed moisture is good to excellent). For canola, the `safe' rates of seed row N for canola are the same for ammonium nitrate and urea. There is no information available on the relative `safety' of ammonium nitrate versus urea on flax.
Crop type
Cereal grains are treated as a group and are more tolerant of seed row N than canola, mustard and flax. Within the cereal group, oat is slightly more tolerant than barley, which is slightly more tolerant than wheat. Canola is slightly more tolerant than flax.
Seeding depth and seed quality
Poor quality seed and an excessive seeding depth makes the crop more vulnerable to injury from seed row N. Using seed with a high percentage germination and vigor, and seeding relatively shallow, encouraged rapid crop emergence and reduces the potential for damage from seed row N.
Nitrogen fertilizer sources
.Ammonium nitrate (34-0-0)
- contains nitrogen in both the ammonium and nitrate form,
- less subject to volatilization losses than urea when surface applied without incorporation,
- more subject to leaching losses on sandy soils,
- used with ammonium phosphate to make the common fertilizer grades 23-23-0 and 26-13-0.
Ammonium sulphate (21-0-0-24S; 20-0-0-24S and 19-3-0-22S)
- 22-24% sulphate-sulphur which is the plant available form,
- used for direct application as both a nitrogen and sulphur source,
- 20-0-0-24S and 19-3-0-22S are granular products more suitable for blending than 21-0-0-24S,
- more acidifying than other nitrogen fertilizers. Do not use continuously or at high rates on acid soils.
- subject to volatilization losses when not incorporated on high pH soils (pH 7.5 or higher).
Urea (46-0-0)
- highest analysis dry nitrogen fertilizer,
- used for direct application or combined with phosphate to make N-P fertilizer such as 27-27-0 and 17-34-0,
- more subject to volatilization losses than 34-0-0 when not incorporated into the soil. Significant losses can occur when urea is applied under warm dry conditions to sandy soils, forages with a heavy thatch and on alkaline soils (pH 7.5 or higher).
Anhydrous ammonia (82-0-0)
- suitable for fall or spring application for annual crops,
- must be knifed into the soil to a depth of 8-15 cm,
- liquid under pressure; changes immediately to ammonia gas when released into the soil. The soil must be closed behind the applicator shank to prevent the ammonia gas from escaping.
Caution: Anhydrous ammonia is a pressurized gas. Everyone involved in the handling and use of ammonia should be aware of the need for caution.
Urea - ammonium sulphate (34-0-0-11S)
- contains 11% sulphur,
- supplies adequate sulphur when used as the nitrogen source on sulphur deficient soils.
Urea - ammonium nitrate solutions (28-0-0)
- a water solution of ammonium nitrate (34-0-0) and urea (46-0-0),
- solutions lend themselves to uniform application and ease of handling,
- can be applied through sprinkler irrigation systems.
Acid nitrogen solutions (24-6-0-4S and 26-0-0-6S)
- contain urea, phosphoric acid and sulphuric acid,
- ease of handling and uniform application advantages of solutions,
- highly corrosive; corrosion resistant materials are required for storage and application equipment.
Phosphate Fertilizer
Phosphate fertilizers do not move readily in soil. Placing the band of phosphate near developing seedling roots of annual crops is most effective. Placement below the depth of seeding may improve availability under dry conditions because the fertilizer is in a moist part of the root zone for a longer period of time than with seed row placement. Broadcast-incorporated applications are less effective than when fertilizer is banded with or near the seed of annual crops. Broadcast application should be two to four times the recommended rates for banding or seed row application.
On established forages, response to broadcast applications may be delayed owing to the slow movement of phosphorus into the root zone. A greater response may occur in the year following application than in the year of application. On soil that is very deficient in phosphorus, phosphate fertilizer should be banded or incorporated before seeding perennial forages.
Phosphorus fertilizer sources
Monoammonium phosphate (11-51-0, 12-51-0 and 11-55-0)
- the most common phosphate fertilizers available in Alberta,
- used for seed row or band application on annual crops, broadcast application on perennial forage or blended with nitrogen fertilizers to give various nitrogen-phosphate fertilizers such as 16-20-0, 23-23-0, 27-27-0, and 26-13-0.
Other phosphate fertilizers are used on a limited basis in Alberta. They include diammonium phosphate (18-46-0), monocalcium phosphate or triple super phosphate (0-45-0), ammonium polyphosphate solution (10-34-0), liquid suspensions made from monoammonium phosphate (10-30-0) and acid solutions made from phosphoric acid and urea (0-34-0-4S).
Potassium Fertilizer
Potassium will move in the soil more readily than phosphorus, but for annual crops, potassium fertilizers are more efficient when drilled with the seed or banded. Broadcast applications can be used at about twice the rate used for drill-in application. The maximum amount that may be safely placed with the seed of cereals is 35 lb/ac. For small-seed crops such as canola or flax, the maximum safe rate with the seed is 15 lb/ac. Broadcast or band applications can be made in either fall or spring.
Potassium fertilizer sources
Muriate of potash (0-0-60 or 0-0-62)
- most commonly used potassium fertilizer in Alberta,
- used directly as a broadcast application or in blends with phosphorus and nitrogen fertilizers to make fertilizer grades such as 10-30-10, 8-24-24, 13-13-13, etc.
Sulphur Fertilizer
Sulphur in the sulphate form moves readily in moist soils. Therefore soluble sulphate fertilizers provide an available sulphur source either as broadcast, drill-in or band applications. Elemental sulphur and gypsum can also be used as sulphur fertilizers.
Sulphur fertilizer sources
Ammonium sulphate (21-0-0-24S, 20-0-0-24S and 19-3-0-22S)
- contains 22-24% sulphate sulphur,
- used directly as both a nitrogen and sulphur source or combined with ammonium phosphate to produce 16-20-0-14S or with urea to produce 34-0-0-11S.
Urea-ammonium sulphate (34-0-0-11S)
- contains 11% sulphur,
- not as acidifying as ammonium sulphate and therefore preferable for use on acid soils that are sulphur deficient.
Ammonium phosphate-sulphate (16-20-0-14S and 17-20-0-15S)
- made from monoammonium phosphate and ammonium sulphate,
- common source of nitrogen, phosphorus, and sulphur for broadcast and drill-in application.
Sulphur bentonite (90% S)
- elemental sulphur fertilizers containing 10% bentonite clay,
- a granular product that can be blended with other fertilizers except ammonium nitrate,
- elemental sulphur must be converted to sulphate sulphur before it is available to plants.Conversion to the sulphate form is carried out by soil bacteria and requires several months under warm, moist soil conditions. The rate of conversion is very slow unless fine particles of sulphur are mixed into the soil. Band application or incorporation of intact granules results in slow conversion to sulphate, Allowing the granules on the soil surface to be dispersed by rain or freezing and thawing before incorporation, will increase the rate of conversion to sulphate.
Gypsum (CaSO4, 2H2O)
- contains 18% sulphur in the sulphate form but is not as soluble as ammonium sulphate,
- supplies both calcium and sulphur
Table 7. lb/ac of fertilizer required to supply a given rate of nutrients.
Fertilizer
Formulation |
lb/ac of nitrogen (N) required |
20 |
30 |
40 |
50 |
60 |
70 |
80 |
100 |
120 |
140 |
|
(lb/ac of fertilizer required) |
21-0-0 (24S) |
95 |
143 |
190 |
238 |
286 |
233 |
- |
- |
- |
- |
20-0-0 (24S) |
100 |
150 |
200 |
250 |
300 |
350 |
|
19-3-0 (22S) |
105 |
158 |
210 |
263 |
316 |
368 |
34-0-0 |
58 |
87 |
116 |
145 |
174 |
203 |
232 |
290 |
348 |
406 |
46-0-0 |
44 |
65 |
87 |
109 |
133 |
156 |
178 |
217 |
261 |
304 |
82-0-0 |
24 |
37 |
49 |
61 |
73 |
85 |
98 |
122 |
146 |
171 |
27-14-0 |
74 |
11 |
148 |
185 |
222 |
259 |
296 |
- |
- |
- |
35-15-0 |
57 |
86 |
114 |
143 |
171 |
200 |
229 |
286 |
343 |
- |
23-23-0 |
87 |
130 |
174 |
217 |
261 |
304 |
- |
- |
- |
- |
27-27-0 |
74 |
111 |
148 |
185 |
222 |
259 |
296 |
- |
- |
- |
17-20-0 (15S) |
118 |
176 |
235 |
294 |
353 |
- |
- |
- |
- |
- |
16-20-0 (14S) |
125 |
188 |
250 |
312 |
375 |
- |
- |
- |
- |
- |
Fertilizer
Formulation | lb/ac of phosphate (P2O5) required |
10 | 15 | 20 | 25 | 30 | 35 | 40 | 45 | 50 | 60 |
| (lb/ac of fertilizer required) |
| 11-55-0 | 18 | 27 | 36 | 45 | 54 | 64 | 73 | 82 | 9 | 109 |
| 11-51-0,12-51-0 | 20 | 29 | 39 | 49 | 59 | 67 | 78 | 88 | 98 | 118 |
| 18-46-0 | 22 | 33 | 43 | 54 | 65 | 76 | 87 | 98 | 109 | 130 |
| 17-34-0 | 29 | 44 | 58 | 73 | 88 | 103 | 116 | 131 | 146 | 176 |
| 8-38-15 | 26 | 39 | 53 | 66 | 79 | 92 | 105 | 118 | 132 | 158 |
| 23-23-0 | 44 | 66 | 87 | 109 | 130 | 152 | 174 | 196 | 217 | 261 |
| 27-27-0 | 37 | 56 | 74 | 93 | 111 | 130 | 148 | 167 | 185 | 222 |
| 16-20-0 (14S) | | | | | | | | | | |
| 17-20-0 (15S) | 50 | 75 | 100 | 125 | 150 | 175 | 200 | 225 | 250 | 300 |
| 27-14-0 | 71 | 107 | 143 | 179 | 214 | |
Fertilizer
Formulation | lb/ac of potash (K2O) required |
10 | 20 | 30 | 40 | 50 | 60 | 80 | 100 |
| (lb/ac of fertilizer required) |
| 0-0-60,0-0-62 | 17 | 33 | 50 | 68 | 85 | 100 | 133 | 167 |
| 8-38-15 | 67 | 133 | 200 | 267 | - | - | - | - |
| 8-2-24,6-24-24 | 42 | 83 | 125 | 167 | 208 | 250 | 333 | 417 |
| 13-16-10(11S) | 100 | 200 | 300 | - | - | - | - | - |
| 14-14-7 | 144 | 286 | - | - | - | - | - | - |
Fertilizer
Formulation | lb/ac of sulphur (S) required |
| 5 | 10 | 15 | 20 | 25 | 30 | 40 |
| (lb/ac of fertilizer required) |
21-0-0 (24S),
20-0-0 (24S) | 21 | 42 | 62 | 83 | 104 | 125 | 167 |
| 19-3-0 (22S) | 23 | 45 | 68 | 91 | 114 | 136 | 182 |
| 16-20-0 (14S) | 36 | 71 | 107 | 143 | 180 | |
| 17-20-0 (15S) | 33 | 67 | 100 | 133 | 167 | - | |
| 34-0-0 (11S) | 48 | 95 | 140 | 182 | - | - | |
| 10-30-10 (5S) | 100 | 200 | - | - | - | - | |
| Gypsum (18S) | 27 | 55 | 82 | 110 | 137 | 165 | |
| Sulphur bentonite (90S) | - | - | 17 | 22 | 28 | 33 | 44 |
|
|