Nitrogen Requirements for Winter Wheat Depend on Type of ProductionMon, 26 Sep 2011 16:11:49 CDT
The amount of nitrogen (N) needed for most crops is based on yield goal. However, the N required for winter wheat depends whether the production is for harvesting grain only, grazing and grain (dual-purpose) or forage only. Phosphorus (P) and potassium (K) needs are based on the sufficiency levels of those nutrients in the soil.
The soil test interpretations for P and K are similar for all 3 wheat systems. However, the current soil OSU test interpretation does not address all these situations individually for N requirement, so they are highlighted below to aid your fertilizing decision.
1. Grain only
The N fertilizer rate for grain only winter wheat is calculated by subtracting the soil test N value (nitrate-N) from the N requirement for the yield goal selected. The realistic yield goal is the average yield of the last 5 years plus 20%. We recommend 2 lbs of N per bushel of wheat. Therefore, the N requirement for grain only wheat is:
N (lbs./acre) = 2 x yield goal (bu./A) – soil test N (lbs./A)
2. Grazing and grain (dual purpose)
If the wheat is intended for grazing and grain production, additional N needs to be considered to replace N removed as beef. Two pounds of N are still needed to produce one bushel of grain, but an additional 30 lbs. N are needed to produce 100 lbs. of beef or 1000 lbs. of forage grazed. Hence, the N requirement for dual-purpose wheat is:
N (lbs./acre) = 2 x yield goal (bu./A) + 0.3 x beef (lbs./A) – soil test N (lbs./A)
3. Forage only
If the field is planned for graze out or harvesting for hay, the N rate is based on the expected forage yield. The requirement is 60 lbs of N per ton of wheat forage, which is similar to other cool season crops. So, the N requirement for forage wheat is:
N (lbs./acre) = 60 x forage yield goal (tons/A) – soil test N (lbs./A)
Our thanks to Dr. Hailin Zhang, email@example.com, and Dr. Jeff Edwards, firstname.lastname@example.org, with Oklahoma State University's Department of Plant and Soil Sciences for providing this article on nitrogen requirements from the Extension News.
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