Fertilizing Winter Wheat
Winter wheat’s demand for N in the fall is low and supplying high rates of N directly to the crop can reduce winter survival by causing excessive fall growth. Normal recommendations are not to apply N with the seed, but if soils are very low in N then 20-30 lbs can be applied to encourage early growth. Usually enough N is supplied with seed-placed phosphorus (P). Higher seed-placed rates could be applied depending on row spacing, seed and fertilizer spread, soil texture, soil moisture and N source (for example in clay soils with good soil moisture, on narrow rows with lots of scatter between the seed and fertilizer granules). Total seed-placed fertilizer, including P and potassium, should not exceed 175 lbs/acre, due to the salt effect of the fertilizers.
All N can be applied in the fall but there are risks involved. Pre-plant banding can disrupt the integrity of the seedbed - reducing seedling establishment, lowering the snow-trapping potential of the stubble and increasing the risk of winterkill. You can side-band or mid-row band but fall-applied N can leach or denitrify. These methods work best in a dry fall and spring and so are risky here in the Red River Valley. Broadcast nitrogen on the soil is not recommended as the risk of loss is high. Nitrogen applications on snow are not recommended. Many producers apply the majority of N in the fall, and top up the remainder in the spring based on estimated nitrogen loss, stand assessment, and economics of both grain and fertilizer prices.
Applying N in the spring must be early enough to meet crop demand. Winter wheat uses about 30-40% of its N by the 5-6 leaf stage (the start of stem elongation) and the remaining 60-70% from stem elongation to maturity. Methods of application include mid-row banding, broadcasting, and dribble banding or spoke wheel application (liquid forms of N).
A variety of N sources are available, each with advantages and disadvantages. Anhydrous ammonia (NH3) can be banded in the fall at seeding or in spring but injection into the established crop may physically reduce the stand. Closure of the injection slot is critical to minimize ammonia loss. Urea can be banded or broadcast but losses due to volatilization risks are greater under high temperatures and high soil pH. Liquid urea-ammonium nitrate (UAN) has a lower risk of volatilization due to its nitrate portion but is more susceptible to leaching and denitrification in wet soils. Use of Agrotain, a urease inhibitor, to treat urea or UAN can delay volatilization losses for up to 14 days. ESN, a controlled release nitrogen fertilizer from Agrium, can minimize N losses by slowly releasing N, providing controlled feeding during fall establishment and early spring growth. Be wary of seed-placing too much ESN, if the coating has fractured its toxicity is similar to urea and stand thinning is expected. Soils may be too cool to release sufficient nitrogen from a spring application of ESN.
Always soil test prior to winter wheat seeding to determine appropriate N application and fertilize to according to the recommendation. Generally insufficient N was applied if protein levels end up less than 11.5%. Fertilizing to meet your yield potential should provide adequate protein at harvest.
