关键词: 夏玉米, 夏玉米, 华北地区, 磷, 利用效率

Abstract: Taking solar greenhouse soil of different planting years in Yan’an as the research object, soil physicochemical indexes are measured. Classification criteria for soil nutrients in the 2nd National Soil Survey and Nemorrow formula are used in this study. The results indicated that the pH value of 5 years greenhouse soil was 8.46, which was alkaline - strong alkaline, while that of 20 years was 7.54 of medium-light alkaline, indicating that the soil tended to be acidification with the increase of planting years. Soil total salt content of 5 years greenhouse was 0.70 g/kg, which was medium salinized soil, and that of 20 years was 1.17 g/kg, which was strong salinized soil. The secondary salinization was obvious with the increase of planting years. Nutrient analysis showed that soil organic matter was 17.53 g/kg and 20.15 g/kg of 5 and 20 planting years, available nitrogen was 93.47 mg/kg and 159.80 mg/kg, available phosphorus was 54.47 mg/kg and 71.85 mg/kg, available potassium was 123.05 mg/kg and 164.23 mg/kg. Available nitrogen content was relatively low. Soil organic matter, available nitrogen, available phosphorus, available potassium was higher in soil of long planting years. Soil integrated fertility was in the third class, fertility condition was ordinary. The integrated fertility index (P) of 20 years was 1.55, which was little higher than that of 5 years (1.12). Thus, the effects of planting years on soil fertility are great.