T/NAASS 067-2023 Ningxia cabbage nitrogen and phosphorus leaching prevention and control technical regulations

Scope

Scope: This protocol defines the terms and definitions, source reduction techniques, process blocking techniques, and end-of-process treatment and harvesting for non-point source pollution of nitrogen and phosphorus in open-field lettuce production due to irrigation and fertilization. This protocol applies to open-field lettuce production under sprinkler irrigation conditions in Ningxia. Main technical content: 3. Terms and definitions The following terms and definitions apply to this document. - Soil nitrogen and phosphorus leaching: The process of nitrogen and phosphorus migrating from the lettuce root zone through subsurface leaching due to irrigation and fertilization. - Source control techniques: Techniques that determine the total nutrient requirements based on target lettuce yield, control fertilizer input, and effectively control soil nitrogen and phosphorus leaching at the source. - Process blocking techniques: Techniques that effectively block soil nitrogen and phosphorus leaching during lettuce growth through water-saving irrigation, organic-inorganic fertilizer combination, and integrated water-fertilizer management. - End-of-process treatment techniques: Techniques that effectively block soil nitrogen and phosphorus leaching after the fourth-season (autumn) lettuce harvest, such as returning harvest residues to the field and controlling winter irrigation water volume. 4. Ningxia lettuce nitrogen and phosphorus leaching prevention and control technologies The peak periods of nitrogen and phosphorus leaching in lettuce soil are during winter irrigation, the first spring crop, and the third-season autumn crop after basal fertilization and three irrigation applications after top-dressing. By controlling irrigation and fertilizer quantities, improving water and fertilizer utilization efficiency, and reducing nitrogen and phosphorus leaching, the specific target yields, fertilizer, and irrigation quantities for each season are shown in T

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