Nitrogen fertilizer is usually needed every season by small grain crops. The amount needed depends on soil type, previous crop, rainfall, irrigation, projected yield, and quality goals. Under some circumstances, it may be necessary to apply phosphorus, potassium, sulfur, or zinc; perform soil tests before sowing to determine whether fertilizers are needed.
The nitrogen status of a small grain crop is best monitored during the season using tissue analysis. Since tillers and heads are formed in the very early growth stages, adequate nutrient levels in the root zone at this time are important for attaining maximum yield. Careful soil sampling and analysis are necessary for determining soil nutrient levels and fertilizer requirements.
Soils & Soil Fertility