Fig. 3: The total maximum transformation number (MTN) of DOM molecules in different biochemical categories under different fertilization treatments based on the PMD network.

CK no fertilization added and complete removal of crop straw, NK urea and potassium chloride, NP urea and calcium-magnesium phosphate, NPK urea, calcium-magnesium phosphate, and potassium chloride, NPKgm NPK chemical fertilization plus green manure, NPKpm NPK chemical fertilization plus pig manure, NPKst NPK chemical fertilization plus rice straw.