Symptoms of nitrogen deficiency in wheat: Slow growth of plants, individual dwarfing, reduced tillering; faded leaf color, yellowing of old leaves, premature decline; red and purple or reddish stems and leaves; slender roots, reduced total roots; Incomplete, smaller ear. Wheat nitrogen excess symptoms: growing over-prosperous, causing leggy; leaf area increased, the darker leaves, resulting in Yu cover; mechanical organization is not well-developed, easy lodging, susceptible to diseases and insect pests, cut production is particularly serious, quality deterioration. Sandy and organic-poor soils, organic fertilizers that do not use basal fertilizers or use large amounts of high-carbon-nitrogen ratios are prone to nitrogen deficiency symptoms. Former crops with excessive nitrogen application, excessive topdressing nitrogen, too late, partial nitrogen fertilizer, prone to excess nitrogen disease. The diagnostic index of soil available nitrogen (in N) from tillering to jointing stage is: less than 20 mg/kg, lacking; 20–30 mg/kg, potential lack; 30–40 mg/kg, normal; Above 40 mg/kg, high or excessive. When the total nitrogen (N) of the functional leaf in jointing stage of wheat is lower than 35 mg/kg (dry weight), it is lacking; 35-45 mg/kg is normal; more than 45 mg/kg is excessive. The prevention and control measures of nitrogen deficiency in wheat are mainly to fertilize the soil and improve the soil nitrogen supply capacity. When a large number of organic fertilizers with high carbon and nitrogen ratios, such as straw, are used, it is necessary to pay attention to the combination of available nitrogen fertilizer; when ploughing and soil preparation, a certain amount is applied. The quick-acting nitrogen fertilizer is used as a base fertilizer; for nitrogen deficiency caused by uneven soil fertility, it is necessary to timely apply the available nitrogen fertilizer. Wheat nitrogen excess control measures are mainly based on the nitrogen requirement characteristics of the crops at different growth stages and the characteristics of soil nitrogen supply, timely and appropriate topdressing nitrogen fertilizer, strict control of dosage, avoiding topdressing nitrogen fertilizer too late; under the premise of rational rotation, Based on the rotation system, determine the appropriate amount of nitrogen application; rational application of phosphorus and potassium fertilizer, in order to maintain the balance of nitrogen, phosphorus and potassium in the plant.