大棚内由于连年种植蔬菜，致使棚内土壤营养元素不能满足蔬菜生长发育的需要，影响蔬菜的产量和品质。所以，应采取以下措施加以改造：　　1．缺N。其症状是植株矮小，叶色变淡或发红，茎短而细，茎部叶片变黄，茎色也有改变，并发展很快，干燥后呈褐色。补救措施：发现缺氮时? Due to the continuous cultivation of vegetables in the greenhouse, the nutrition elements in the shed can not meet the needs of vegetable growth and development, affecting the yield and quality of vegetables. Therefore, we should take the following measures to be modified: 1. N Its symptoms are short plants, pale or reddish leaf color, short and thin stalks, stem yellow leaves, stem color has changed, and the rapid development of brown after drying. Remedy: Found when nitrogen deficiency?