西安市菜田施肥现状与土壤肥力状况
Fertilizers Application and Nutrient Status of Soil in the Vegetable Field of Xi’an City

为摸清西安市菜田施肥及土壤养分现状, 按不同种植年限，调查了西安市8个涉农区县露地、大棚和日光温室全部菜田（共422个样本）肥料施用情况，并采集0~20 cm土样进行土壤养分、pH及盐分分析。结果表明，露地蔬菜氮、磷、钾肥平均用量分别为N 327.0 kg/hm2 、P2O5 186.0 kg/hm2、K2O 138.0 kg/hm2，氮、磷肥用量偏高，钾肥用量适宜。大棚蔬菜氮、磷、钾肥平均用量分别为N 868.5 kg/hm2 、P2O5 544.5 kg/hm2、K2O 496.5 kg/hm2，日光温室蔬菜氮、磷、钾肥平均用量分别为N 883.5 kg/hm2 、P2O5 684.0 kg/hm2、K2O 724.5 kg/hm2，设施蔬菜化肥用量严重超量，特别是磷肥最为严重。随种植年限增长，露地蔬菜氮、磷、钾肥施用量有明显提高趋势，而大棚与日光温室蔬菜化肥施用量与种植年限长短关系不大；菜田有机质质量分数均属于较低水平，应加大有机肥投入；露地蔬菜土壤养分质量分数适中，设施蔬菜土壤养分质量分数属于偏高水平，这与施肥现状调查中设施蔬菜过量施用化肥的结果相一致；设施蔬菜土壤硝酸盐质量分数超过露地蔬菜的2.2~2.3倍，盐分质量分数超过露地蔬菜的2.2~3.3倍，土壤硝酸盐和盐分累积十分明显，对蔬菜生产已形成潜在不良影响。今后应严格控制化肥的施用，通过测土配方施肥技术优化施肥结构、用量与比例，防止土壤次生盐渍化等的发生。
The fertilizer application in open field, plastic tunnel and greenhouse vegetable production in eight agricultural counties of Xi’an city was surveyed. The nutrients mass fractions, pH and soluble salts in top soil (0-20 cm) with different growing years were determined, in order to clarify the fertilizer application and soil nutrient status in Xi’an vegetable fields. The results showed that the average fertilizer application was N 327.0 kg/hm2, P2O5 186.0 kg/hm2 and K2O 138.0 kg/hm2 in open field, N 868.5 kg/hm2, P2O5 544.5 kg/hm2 and K2O 496.5 kg/hm2 in plastic tunnel, and N 883.5 kg/hm2, P2O5 684.0 kg/hm2 and K2O 724.5 kg/hm2 in greenhouse, respectively. Excessive nitrogen and phosphorus fertilizers and feasible amount of potassium fertilizer were used in open field. Excessive fertilizers, especially the phosphates was used in plastic tunnel and greenhouse. The application of three main fertilizers increased greatly with the increasing of planting years in open field. However, there is little correlation between the planting years and the amounts of fertilizer application in plastic tunnel and greenhouse. The mass fraction of organic matter in vegetable field was at lower level. It is urgent to increase organic fertilizer to maintain the healthy development of vegetable production. The nutrient mass fraction in open field soil is moderate, but in plastic tunnel and greenhouse soil is higher, which are in agreement with the survey results of fertilizer application in local vegetable production. The nitrate mass fraction in plastic tunnel and greenhouse soil is 2.2-2.3 fold and salt mass fraction 2.2-3.3 fold compared to the open-field soil. The obvious accumulation of salt and nitrate in soil is threatening vegetable production. It is suggested that fertilizer application in vegetable production should be strictly controlled and follow soil testing and fertilizer recommendation technology to optimize fertilization constitution and