FERTILIZATION OF SMALL GRAINS
A soil test is highly recommended in the spring. A good soil test will eliminate guessing on soil nutrient test levels and will easily pay for themselves in fertilizer savings or better crop yields. A top soil to 10-12" . If you grow crops with high nitrogen use before like potatoes and vegetables a subsoil sample of 10-20" is recommended.
NITROGEN
Use a yield goal method to determine nitrogen needs of the crop. First estimate a realistic yield goal. For irrigated small grains some yield goals are in the following table:
| Barley | Yield Goal
(bu/A) |
Wheat | Yield Goal
(bu/A) |
Other Grains | Yield Goal |
| Triumph/Comargue | 160 | Hard Red Spring | 120 | Oats for Grain | 100 bu/A |
| WB501 | 155 | Hard Red Winter | 130 | Oats for Hay | 4-5 Tons/A |
| Other Feed Barleys | 150 | Hard White Spring | 120 | Rye | 110 bu/A |
| Moravian 14 | 140 | Soft White Spring | 145 | ||
| Other Malt Barleys | 110 | Durum | 110 |
Total Nitrogen Requirement = Crop Coefficient x Yield Goal in bu../Acre
Below is a table of crop coefficients for various small grain crops:
| Crop | Crop Coefficient |
| Feed Barley | 1.40 |
| Malt Barley | 1.20 |
| Red Wheat | 1.75 |
| White Wheat | 1.80 |
| Durum Wheat | 1.75 |
| Oats for Grain | 1.00 |
| Oats for Hay | 35 |
| Rye | 1.1 |
(For example for triumph feed barley it would be: 160 bu/A. X 1.4 = 224 units/A Nitrogen)
Use a Nitrogen budget and soil test results to determine what the actual field will need:
Nitrogen requirement: ___________________________
Surface soil Nitrate-N: _____________________________
Subsoil Nitrate-N /2 : _____________________________
Organic Matter N Release: _________________________
Manure N Release: _______________________________
Irrigation Water Nitrate: ___________________________
NITROGEN FERTILIZER REQUIRED:_______________ (Lbs./A)
(Subtract the various nitrogen forms available from the nitrogen requirement to get the nitrogen required)
Organic matter release in the SLV = 10 x % Organic Matter in topsoil which is usually 10 units nitrogen/A.
In Warmer areas the O.M. release will be 20 x O.M.% or even 30 x O.M. %.
Irrigation well water supplies some nitrogen, but varies with location and depth of well. Use the following table to interpret water test results to estimate the nitrogen supplied by the irrigation well water. On shallow rooted grain crops like Coor's M-14 only subtract ½ of subsoil nitrate levels and ½ of irrigation water nitrates from total nitrogen requirement.
|
Nitrogen Credit from Irrigation Water | |||||
| No3N-N in Water | Water Applied (inches) | ||||
| ppm | 6 | 12 | 18 | 24 | 30 |
| 1 | 1 | 2 | 4 | 5 | 7 |
| 2 | 3 | 5 | 8 | 11 | 14 |
| 3 | 4 | 8 | 12 | 16 | 20 |
| 4 | 5 | 11 | 16 | 22 | 27 |
| 5 | 7 | 14 | 20 | 27 | 34 |
| 6 | 8 | 16 | 24 | 32 | 41 |
| 7 | 9 | 19 | 28 | 38 | 47 |
| 8 | 11 | 22 | 32 | 43 | 54 |
| 9 | 12 | 24 | 36 | 49 | 61 |
| 10 | 13 | 27 | 40 | 54 | 67 |
| 12 | 16 | 30 | 45 | 60 | 75 |
| 14 | 19 | 38 | 57 | 76 | 95 |
| 16 | 22 | 43 | 65 | 86 | 108 |
| 18 | 23 | 49 | 73 | 97 | 122 |
| 20 | 27 | 54 | 81 | 108 | 135 |
Calculating release of nutrients from manures is always tricky and is best done with experience and a nutrient test of the manure to be used. Soil temperature can influence release as well from year to year. Use the table below to estimate nutrient content on a dry basis of various manures.
| Manure | Total N | Ammonium N | Phosphorus | Potassium | Sulfur |
|
Lbs./Ton | |||||
| Non-Composted Poultry | |||||
| Turkey | 35 | 4 | 53 | 37 | 6 |
| Fresh Broiler | 78 | 6 | 51 | 53 | 9 |
| Fresh Layer | 79 | 8 | 125 | 67 | 16 |
| Aged Layer | 43 | 9 | 164 | 79 | 14 |
| Non-Composted Dairy/Steer | |||||
| Fresh Dairy separator solids | 43 | 1 | 17 | 12 | 10 |
| Fresh Dairy corral scrapings | 47 | 2 | 26 | 141 | 12 |
| Aged Dairy separator solids | 41 | 1 | 13 | 8 | 9 |
| Aged Dairy corral scrapings | 26 | 5 | 31 | 66 | 8 |
| Composts | |||||
| Broiler | 38 | 2 | 86 | 50 | 11 |
| Dairy | 27 | 1 | 27 | 57 | 9 |
| Dairy/Steer | 33 | 0 | 17 | 51 | 9 |
| Dairy/Poultry | 34 | 2 | 39 | 75 | 29 |
If you don't have soil sample results the top and subsoil nitrogen residual can be estimated:
After a wet winter you'll want to subtract 20 - 30 units from these amounts and after a dry winter you'll want to add 20 - 30 units nitrogen to these residual amounts.
Nitrogen Timing: Small grains do best when all or most of the fertilizer is applied preplant. Applying 20 - 40 units/A nitrogen during tillering can increase tillering. Applying 30 units/A at early boot can increase protein levels in grain which is desirable in certain wheats. They need ready access to fertilizer during tillering early and later the extensive root system can follow any leached nitrogen down the soil profile. Broadcast is a very effective way to apply fertilizers. Banding has been worked well if the bands are close enough can really help the availability of phosphorus in phosphate fixing soils. Applying fertilizer with the seed can work very well with phosphate blends like 11-52-0, 18-46-0 at low amounts like 50 lbs/A, but applying too much nitrogen with the seed at planting can result in salt injury.
Nitrogen and water. If the grain crop is water short such as in a dryland crop, water will be the limiting requirement and extra nitrogen will not increase yields. Under a water rich field early season adequate nitrogen is key to high yields. Again, use a realistic yield goal in these calculations.
Use a soil sufficiency method to determine any needed phosphorus:
| Mehlich test results
ppm |
Olsen Sodium Bicarbonate results
ppm |
Phosphate Requirement in Lbs./A P2O5 |
| Above 60 | Above 31 | None needed |
| 40 - 50 | 21 - 31 | 25 Lbs./A |
| 30 - 40 | 15 - 21 | 40 Lbs./A |
| 20 - 30 | 10 - 15 | 60 Lbs./A |
| 10 - 20 | 5 - 10 | 80 Lbs./A |
| 0 - 10 | 0 - 5 | 100 Lbs./A |
Phosphorus availability varies a lot in western soils. Adjustments should be made to these recommendations.
If you don't have soil test results fields with a good history of potatoes will need 0-25 Lbs./A phosphorus and grain on grain situations it can vary from 40 - 80 Lbs./A.
Potassium
Most western soils have sufficient potassium levels for a small grain crop but some areas may need some additional potash applied. Use the following table to determine amounts needed:
| K test value in ppm | less than 50 | 50-80 | 80-120 | 120-175 | 175- |
| K needed in Units./A | 100 | 70 | 50 | 30 | 0 |
Sulfur
Small grains are a moderate user of sulfur which is a mobile nutrient like nitrogen which can move with soil water. Sulfur availability should be 1 unit of sulfur to 4 units nitrogen. Sulfur in elemental form can also help the availability of phosphorus.
Micronutrients
Iron: If the soil levels are below 4.5 ppm additional iron may be needed. There are foliar forms. In some cases iron use by the plant may be blocked by excess lime in the soil which is difficult to correct.
Other micro-nutrients are usually not needed for small grains crops. In certain localized areas micro-nutrients problems may occur. At times this may not be a result of that certain micronutrient being deficient, but a nutrient imbalance may block the use of another. An example is excess potassium blocking magnesium uptake or the iron lime example above. Micro-nutrient problems sometimes take time to diagnose and find a solution. Applying micro-nutrient blends with every nutrient can solve the problem, but this shotgun approach is usually much more expensive than applying just the nutrient one needs.
Note: This information should only be used as a guide. Adjustments for local conditions must always be made.