Nitrogen (N) is essential for vigorous growth, high yield and quality of mustard. Nitrogen is essential in the production of plant proteins and chlorophyll, and is needed in the greatest amount compared to the other macronutrients. Nitrogen uptake and utilization takes place throughout the entire growth cycle. When plants are deficient in N they will have pale green to yellow foliage and the plants will often be spindly. Yellowing of the older leaves is another indication that the mustard may be deficient in N. Nitrogen is distributed from old leaves to younger leaves in the plant resulting in deficiency symptoms first appearing on older leaves. On a canopy level, when a crop is N deficient, the canopy will likely be thin and open and the flowering period will be shortened leading to reduced pod set and lower yield.
Mustard, like canola, responds strongly to N fertilization and yield increases of 30% or more are common. Recommended rates of N are 50 to 80lbs/acre of actual N in soils where N is deficient, but it is best to follow the soil test recommendations. Increasing N levels above the soil test recommendation does not always lead to further increased yields. The highest response to added N occurs when moisture is not limiting. In dry years, N rates near the low range of the recommendation will be adequate since realistic target yields will be lower than when moisture is not a limiting factor.
Mustard seed is small and very sensitive to seed-placed N fertilizer, similar to that of canola. If nitrogen is required in excess of the safe rates for seed-applied N, or if moisture is limiting, should be side banded or mid-row banded. For the best response, N should be applied at the time of seeding with a direct seeding system. When this is not possible, N fertilizer should be banded in the fall. If topdressing nitrogen use a urease inhibitor to minimize volatilization losses.
Safe rates of seed-placed urea N for mustard in actual pounds per acre (good-to-excellent soil moisture):
| 1 inch spread* | 2 inch spread* | 3 inch spread* | |||||||
| Soil texture | (disk or knife)** | (spoon or hoe) | (sweep) | ||||||
| Row spacing | Row spacing | Row spacing | |||||||
| 6" | 9" | 12" | 6" | 9" | 12" | 6" | 9" | 12" | |
| SBU*** | SBU | SBU | |||||||
| 17% | 11% | 8% | 33% | 22% | 17% | 50% | 33% | 25% | |
| Pounds of actual N per acre‡ | Pounds of actual N per acre‡ | Pounds of actual N per acre‡ | |||||||
| Light | 10 | 5 | 0 | 20 | 15 | 10 | 30 | 20 | 15 |
| Medium | 15 | 10 | 5 | 30 | 20 | 15 | 40 | 30 | 20 |
| Heavy | 30 | 15 | 10 | 40 | 30 | 20 | 50 | 40 | 30 |
| * Width of spread varies with air flow, soil type, moisture level, amount of residue and other soil conditions, so it must be checked under field conditions. ** Some openers give less than 1" spread. *** Seedbed Utilization (SBU) is the amount of the seedbed over which fertilizer has been spread. Thus, it is a reflection of the relative concentration of fertilizer. SBU (%) is the width of spread divided by the row spacing multiplied by 100. ‡Values are for actual N. To get the pounds of Urea (46-0-0) to apply per acre, divide by 0.46 |
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