连续多年种植蔬菜的老菜地,土壤环境恶化,会造成蔬菜病虫害日趋严重,蔬菜质量下降。土壤恶化表现:一是线虫、病菌、残留毒素增多。蔬菜连作造成病菌及毒素在土壤中积累,根系因受害而腐烂、甚至全株死亡。线虫危害也会加重。二是土壤板结,有机质匮乏,由于大量施用二铵、复合肥、化肥、忽视有机肥施用,造成土壤板结,透气性降低,蔬菜根系发育不良,易受病 For many years old vegetables growing vegetables, deteriorating soil environment, vegetable diseases and insect pests will cause more and more serious, vegetable quality declines. Soil deterioration: First, nematodes, germs, residual toxins increased. Vegetable continuous cropping causes bacteria and toxins to accumulate in the soil. The root system is decayed by the victimization and even the entire plant dies. Nematode hazards will increase. Second, soil compaction, lack of organic matter, due to the large amount of diammonium, compound fertilizer, chemical fertilizer, neglect of organic fertilizer application, resulting in soil compaction, reduced permeability, vegetable root system dysplasia, susceptible to disease