山东省设施菜地土壤次生盐渍化特征及影响因素

Secondary Salinization of Greenhouse Vegetable Soils and Its Affecting Factors in Shandong Province,China

调查和分析了山东省设施菜地土壤次生盐渍化特征和影响因素。2014年全省设施菜地(含瓜类)总面积(日光温室、大拱棚含棚间面积)为64.98×10^(4 )hm^2,占全省菜地面积的35.45%,其中,日光温室25.06×10^(4 )hm^2,大拱棚20.94×10^(4 )hm^2,中小拱棚18.98×10^(4 )hm^2。山东省设施菜地土壤盐分离子组成中阴离子以SO_4^(2-)离子为主,阳离子以Ca^(2+)为主。全省设施菜地约39.73%出现不同程度的盐渍化现象,其中,轻度盐渍化为28.64%,中度盐渍化为8.37%,重度盐渍化为2.29%,盐土为0.43%。在不同设施类型中,盐渍化发生程度为:日光温室>大拱棚>中小拱棚;全省17个市设施菜地次生盐渍化发生程度表现出聊城、莱芜、东营相对较高。全省化肥平均施用量(折纯)为1 624 kg hm^(-2),氮肥(N)、磷肥(P_2O_5)、钾肥(K_2O)施用量(折纯)分别为559.5、465.2、599.3 kg hm^(-2)。通过分析设施菜地土壤次生盐渍化影响因素发现,化肥的高投入是可溶性盐分增加的一个重要原因,但在实际生产中受各种因素影响,未表现出完全线性相关关系;可溶性盐分增加与种植年限密切相关。典型对应分析发现,施肥数量、种植年限均会影响盐渍化程度,但影响各不相同。氮肥、磷肥和钾肥对K^+和Na^+的影响较大;Ca^(2+)和SO_4^(2-)含量受种植年限影响较大,K^+、Na^+、HCO_3^-和Cl^-受种植年限的影响较小;Mg^(2+)受氮磷钾肥和种植年限的影响均较大。

【Objective】Facilitated vegetable cultivation is a general term,encompassing glass greenhouse,sunlight greenhouse and plastic greenhouse,and characterized by high yield and high economic efficiency.However,as facilitated vegetable cultivation is going on in a confined space where temperature,humidity,ventilation and water/fertilizer management,all are different from those in the open field,high fertilizer input,consecutive years of cultivation and improper management make the soils therein liable to have secondary salinization.Shandong Province is an important base of facilitated vegetable production,enjoying great advantages,in China.By studying the soils under greenhouse in Shandong Province and analyze distribution,degree and major causes of secondary salinization in the soils is expected to be able to provide certain data,support and reference for management of secondary salinization in the soils under greenhouse all over the country.【Method】From May to June 2014,soil samples were collected from facilitated vegetable fields in 17 cities of Shandong Province for analysis of total salt and salt content,while a survey was conducted on the farmers.For soil sampling,sampling points were laid out,one every133^333 hm^2,and samples collected evenly from the 0^20 cm soil layer of each sampling point.Soil samples from 8^10 points were blended into one sample.Total soluble salt was determined with the mass method,using water bath,electric ovens,dryer,and 1000ml porcelain evaporating dish;CO3^（2-）and HCO3^-was with the double indicator neutralization method;Cl^-was with the silver nitrate titration method;SO4^（2-）was with the Barium Sulfate Turbidimetry;Ca^2＋and Mg^2＋was with the EDTA complexometric titration;and Na^＋and K^＋was with the flame photometry.For the survey,a questionnaire titled as＂Questionnaire on Basic Situation of Facilitated Vegetable Cultivation＂was distributed for farmers to fill out.It contained the following items：planting type,cropping system,position in land relief,parent soil,soil type,soil texture,irrigation water source,irrigation mode,tillage pattern,restraining factors,etc.The criteria for grading sulfate-type salinized fluvo-aquic soils for the Second National Soil Survey was cited as reference,that is,soils 2^4 g kg^（-1） in total water-soluble salt are sorted as slightly salinized soil,soils 4^6 g kg^（-1） as moderately salinized soil,soils 6^10 g kg^（-1） as severely salinized soil,and soils10g kg^（-1） as saline soil.【Result】Secondary salinization of greenhouse vegetable soils in Shandong was investigated and analyzed.In 2014,the greenhouse vegetable（including melons）land totaled 64.98×10^4 hm^2 in area,accounting for 35.45%of the total vegetable land of the province.Of the greenhouse vegetable land in Shandong,25.06×10^4 hm^2was under sunlight greenhouses;20.94×10^4 hm^2 under large arched plastic huts;and 18.98×10^4 hm^2 under medium and small arched plastic sheds.The salt ions in the greenhouse vegetable soils,consisted mainly of SO4^（2-）-dominated anions and Ca^2＋-dominated cations About 39.73%of the greenhouse vegetable soils in the province suffered salinization varying in degree,and among them,0.43%was slightly salinized,2.29%moderately salinized,8.37%severely salinized and 28.64%saline soils.In terms of salinization degree,the three types of greenhouses displayed an order of,sunlight greenhouselarge arched hutsmall arched shed.In the 17 cities investigated of Shandong Province,Liaocheng,Laiwu,and Dongying was relatively high in secondary salinization degree.The province applied 1 624 kg hm^-2（on nutrient element basis）of chemical fertilizers on average,consisting of 559.5 kg hm^-2 N,465.2 kg hm^-2 P2O5 and 599.3 kg hm^-2 K2O.Analysis shows that among the factors affecting secondary salinization,high chemical fertilizer input ranked first,although in the actual production practice affected by a huge variety of factors,no apparent linear relationship was observed,Instead,accumulation of soluble salts was found closely related to cropping history.Canonical correspondence analysis shows that both input of fertilizers and cropping history would affect salinization degree,though varying in impact.Input of NPK fertilizers was the major factor affecting contents of K^＋,Na^＋and Mg^2＋in the soi,while cropping history was the one affecting contents of Ca^2＋,Mg^2＋and SO4^（2-）,rather than contents of K^＋,Na^＋,HCO3^-and Cl^-.Content of Mg^2＋was significantly affected by both factors.【Conclusion】About 39.73%of the facilitated vegetable land in Shandong Province exhibits a varying degree of secondary salinization.High input of chemical fertilizers is an important cause of the increase in soluble salt,and cropping history is another.It is,therefore,recommended that management of the cultivation under greenhouse should be intensified case-specifically in response to differences in type of greenhouse input of fertilizers and cropping history so as to mitigate the risk or reduce the degree of secondary salinization.