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,大片死亡。土壤恶化的表现: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、复合肥等化肥,忽视有机肥的施用,造成土壤板结,透气性降低,蔬菜根系发育不良,易受病害。三是土壤盐溃化加重。过量施用化肥,土壤中盐离子增多,PH 值升高,盐溃化加重,防碍根系正常吸水,影响植株生长和产量。四是微量元素不足。多年连 For many years, vegetables planted in old vegetable fields, deteriorating soil environment will cause vegetable pests and diseases are becoming more serious, large-scale death. The performance of 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 chemical fertilizer such as diammonium and compound fertilizers, ignoring the application of organic fertilizer, resulting in soil compaction, reduced permeability, vegetable root system dysplasia, susceptible to disease. Third, soil salt worsened. Excessive application of chemical fertilizers, increased salt ions in the soil, PH value increased salt exacerbation, hinder the normal root absorption, affecting plant growth and yield. Fourth, the lack of trace elements. For many years