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 土壤恶化的表现:一是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、复合肥等化肥,忽视有机肥的施用,造成土壤板结,透气性降低,需氧型微生物活性下降,土壤熟化慢,致使蔬菜根系发育不良,易受病害。三是土壤盐渍化加重。过量施用化 Vegetable growing in vegetables for many years, deteriorating soil environment, vegetable diseases and pests will cause more serious deterioration of soil performance: First, vegetable continuous cropping caused by bacteria and toxins accumulated in the soil, root rot due to damage, and even whole plant death Nematode damage Will increase. Second, soil compaction, lack of organic matter. Due to the large amount of fertilizers such as diammonium and compound fertilizers, neglecting the application of organic manure results in soil compaction, decreased air permeability, decreased aerobic microbial activity and slow soil ripening, resulting in poor root growth and susceptibility to diseases. Third, soil salinization worsened. Overexposure