【作者】 袁巧霞；

【导师】 朱端卫；

【作者基本信息】 华中农业大学 ， 植物营养学， 2008， 博士

【摘要】 设施栽培中的土壤次生盐渍化、硝酸盐累积、土壤酸化等问题日益突出,已成为阻碍我国设施农业可持续性发展的瓶颈。针对这种现状,本文围绕着温室栽培中土壤硝酸盐累积这一主线,通过试验研究了温室栽培中水、热、氮对盐渍化土壤氮转化、硝酸盐运移和累积、作物生长发育以及作物氮吸收的影响。主要研究成果包括以下几个方面:1.温室栽培中土壤盐分状况调查及其理化特性分析武汉地区长年温室栽培中土壤的硝酸盐累积量、盐分含量和电导率均高于相邻露地土壤,0～20cm表层土的盐分累积量明显高于20～40cm深层土壤,并且其累积量随温室使用年限的增加而提高;各盐分离子的含量均较露地土壤有大幅度增加,其中以NO₃^-、Cl^-和Ca²⁺的相对富集为主要特征。半年盖棚半年揭棚的塑料大棚中土壤由于在多雨季节受到雨水的淋溶作用,盐分累积量不十分明显,但仍高于相邻露地土壤。对土壤浸提液电导率和盐分化学性质进行了相关性分析。结果表明,土壤浸提液总盐含量（SSC）、Cl^-和Ca²⁺是影响土壤浸提液电导率的主要因素,NO₃^-、K⁺和Na⁺对土壤浸提液电导率直接效应并不明显,而其主要是通过对其它各化学性质的影响对土壤浸提液电导率产生间接效应,这种关系的相关性显著;土壤浸提液离子强度与其电导率亦显著相关,并可表示为I=0.0176EC。2.温室栽培中土壤水、热基本特性利用混合法研究了土壤水分和土壤温度对土壤比热容的影响,结果表明:在不同温度条件下,土壤比热容均随土壤含水率的增加而增加,且在低含水率下比热容增加的速率高于高含水率的情况;土壤比热容亦是温度的函数,且低温时比热容增加速率低于高温时的增加速率。土壤水分和温度的一次项对土壤比热容的影响达极显著水平,但它们之间交互作用的影响并不明显。利用探针法研究了土壤含水率以及土壤初始温度对土壤导热系数的影响,结果表明:在试验因子设定的范围内,土壤导热系数随土壤含水率和土壤初始温度的增加而增加。土壤含水率和土壤初始温度的一次项对土壤导热系数的影响达极显著水平,含水率的二次项对土壤导热系数的影响达显著水平,但土壤初始温度的二次项对土壤导热系数以及它们之间交互作用的影响并不明显。利用压力膜仪测定了温室栽培中土壤的水力特性曲线,结果表明:在0～100kPa吸力范围内,土壤水分含量变化较大:在100～1500kPa吸力范围内,土壤水分特征曲线变化平缓;单位吸力变化引起的含水率变化小,土壤水分的移动能力、导水能力较弱,但土壤持水能力增强,在此基础上建立了水力特征曲线回归模型。3.水、热、氮耦合对温室栽培中土壤水、氮运移特性影响蒸发温度和土壤初始含水量明显影响NO₃^--N向土壤表层的迁移,并随蒸发温度和土壤初始含水量的增加而加强;通过正交回归分析得出影响NO₃^--N迁移速率的因素依次为初始含水量、蒸发温度以及温度与含水量的交互作用;土壤初始NO₃^--N含量以及它与蒸发温度、土壤初始含水量的交互作用对NO₃^--N迁移速率的影响不显著,但它影响土壤中各层的NO₃^--N绝对含量。经过5天蒸发后,NO₃^--N沿垂直剖面分布出现上高下低,并出现一小的回升后逐渐趋于稳定。在不同条件下,温室栽培中土壤垂直剖面的水分分布均表现为上低下高,表层土壤水分梯度变化大。随着蒸发温度的升高,表层土壤含水量逐渐降低,而水分梯度变化涉及到的土层深度越深;随着土壤初始含水量的增加,蒸发结束后表层土壤含水量也逐渐增加,表层土壤水分梯度却随土壤初始含水量的增加而减少;而土壤中的含水量则随土壤初始NO₃^--N含量的增加而增加。4.水、热、氮耦合对温室栽培中土壤硝态氮累积影响通过培养试验研究了温度、水分、施氮量及其耦合效应对温室土壤硝化作用和硝态氮累积的影响。结果表明:温室土壤硝态氮累积量可用“S”曲线Δ（NO₃^-）=e^（a+b/τ）进行定量描述,其硝化过程最大硝化速率、延迟期和最大可能累积量是参数a、b的函数;通过正交回归分析得出影响最大硝化速率的因素依次为温度、含水率、温度与含水率的交互作用、水肥的耦合作用以及施氮量;影响延迟期的因素依次为土壤水分、土壤温度、施氮量以及水肥耦合作用;最大可能累积量与温度、含水率及施氮量的关系呈指数变化,其中施氮量影响最大,温度次之,而这3因素之间的交互作用对最大可能累积量没有明显影响。利用回归模型,可为不同环境及水肥条件下硝态氮累积量及氮利用的有效性预测提供依据。5.水、热、氮耦合对温室栽培中土壤pH和EC影响通过培养试验,研究温度（T）、水分（W）、施氮量（N）及其耦合效应对温室土壤pH及EC的影响。结果表明:随着培养时间延长,温室土壤pH逐渐下降,下降速率可用一级反应模型进行定量描述,N、W、W×N以及T×W对其速度常数的影响大小依次为N＞W＞W×N＞T×W;EC在培养的第1周内快速上升到最大值后略有下降,并在培养后期逐渐趋于稳态值(EC_sty),EC_sty受N、W、T×W、T以及W×N的影响,其中N、W、T×W和T的影响达到极显著水平,W×N的影响达到显著水平;通过减小施氮量及适当调亏灌溉可有效延缓温室土壤酸化和EC升高。建立的pH下降速率常数及EC_sty回归模型可为不同环境及水肥条件下土壤酸化及EC变化预测提供依据。6.硝酸盐累积、pH及EC对水、热、氮影响的敏感性选取同种土质的温室栽培土壤和露地耕作土壤进行培养试验,比较分析2种土壤在培养期土壤硝酸盐累积、pH和EC值变化对土壤水分和施氮量影响的敏感性差异。结果表明:在相同水肥条件下,温室土壤硝酸盐累积、pH下降速率及EC增量明显高于露地耕作土壤;温室土壤硝酸盐累积速率和pH下降速率随土壤水分含量和施氮量的增加而增加,当土壤水分含量为90%FC时2者的变化速率达最大值,而露地耕作土壤硝酸盐累积速率和pH下降速率随土壤水分含量增加先升高后降低,在70%FC处达最大值;温室栽培中土壤硝酸盐累积速率和pH下降速率对施氮量影响的敏感性高于露地土壤;2种土壤EC值均随土壤水分含量和施氮量的增加而增加,露地耕作土壤EC值增量对土壤水分和施氮量影响的敏感性高于温室土壤,但温室土壤在培养期EC绝对增量远高于露地耕作土壤,这种增加使温室土壤盐渍化日趋严重。7.水、氮耦合对温室作物氮吸收影响利用硝酸盐累积较为严重的温室栽培土壤进行番茄栽培试验。灌水量为100%FC、施氮量为150mg/kg的条件最有利番茄植株生长、发育,其植株体内硝酸还原酶活性（NRA）明显高于其它处理而累积的硝酸盐含量却低于其它各处理,且在作物收获后,该处理土壤中残留的硝酸盐及铵态氮含量也明显低于其它各处理。当灌水量为80%FC、施氮量为300mg/kg时,番茄植株生长发育迟缓,枯萎,死亡现象较为严重,其植株体内的NRA相比其它处理为最低,不论是土壤表层还是深层,作物收获后的硝酸盐和铵态氮残留量均处于一个较高水平。对于硝酸盐累积严重的土壤,足量灌溉比调亏灌溉更有利于番茄作物生长发育和氮的吸收。8.温室栽培中土壤硝酸盐积累积的BP神经网络模型采用引入附加动量和自适应学习率的BP神经网络构建了温室栽培中土壤硝酸盐累积的水、热、氮耦合作用模型;利用Matlab6.5对该模型进行了设计,并将设计好的模型对检验样本进行仿真,对BP网络模型仿真结果与回归方程拟合结果进行了比较。结果表明BP网络模型收敛速度快,拟合效果好,泛化能力（网络推广能力）强,预测精度高,完全可以用于温室栽培中土壤硝酸盐累积的水、热、氮耦合作用预测。更多还原

【Abstract】 The phenomena of soil secondary salinization,nitrate accumulation and soil acidification in protected culture are very serious,and have changed into a bottleneck problem to hinder the sustaining development of greenhouse production in China.To meet these problems in this paper,the interaction effects of temperature,moisture and nitrogen on its transformation,transport and accumulation of NO₃^--N,growth and nitrate uptake of plant were studied in the laboratory around the subject of soil nitrate accumulation in greenhouse culture.The conclusion has been drawn as follows:1.The investigation of soil salt and analysis of its physico-chemical properties in greenhouse cultureThe soil nitrate content,salt content and electrical conductivity were higher under perennial protected condition than those under open-field one.The salt contents were significant higher in 0～20cm surface layer soil than those in 20～40cm depth layer soil and the salt accumulation increased with increase of greenhouse age under protected condition. Various salt ionic contents were significant larger in protected-field soil than in open-field soil,and the main characteristic was relative to enrichment of NO₃^-,Cl^-and Ca²⁺.The salt accumulation was no significant in semiannual-cover plastic greenhouse because of eluviations of rainwater in rainy season,but it was apparent higher than that in open-field. The relationships between electrical conductivity of soil extract(EC_5:1) and chemical properties were analyzed.The results indicated that total soluble salt concentration（SSC） and concentration of Cl^-and Ca²⁺ were the most primary factor to influence EC_5:1.The direct effect of NO₃^-,K⁺ and Na⁺ to EC_5:1 was not significant,but they were enlarged by influence of other chemical factors,such as Cl^-、Ca²⁺ and SSC,making the correlation coefficient between EC_5:1 and these factors relatively higher.The ionic strength was related significantly to EC_5:1 which could be estimated by I=0.0176EC.2.The soil hydraulic and thermal properties in greenhouse cultureEffects of temperature and water content on the soil specific heat were studied by mixing method.The results indicated that the soil specific heat increased with increasing soil water content,and the increase rate was higher in low water content than that in high water content.The soil specific heat was also function of temperature,and its increase rate was lower under low temperature condition than that under high one.The linear function of soil temperature and water content had impact on soil specific heat in a highly marked level and their interaction had not attained a significant level.Effects of temperature and water content on the soil thermal conductivity were studied by heat-probe method.The results showed that soil thermal conductivity increased with increasing of soil water content and soil initial temperature in test level.The linear function of soil water content and initial temperature had impact on soil thermal conductivity in a highly marked level and square of soil water content in a significant level,but the square of soil initial temperature and their interaction in a no significant level.A pressure device was introduced to determine soil water retention curve.The results indicated that soil water content changed widely in 0～100kPa suction and it changed gently in 100～1500kPa suction.The change of water content resulted from change of unit suction was light,the mobility and conductivity of soil water were weaker but water retention capability of soil enhanced.A regression model for soil water retention curve was derived.3.Effects of moisture and temperature on water and NO₃^--N transport in greenhouse cultureVaporization temperature and initial soil moisture influenced significantly NO₃^--N transport from deep soil to top soil,and the transport rate increased with the increase of vaporization temperature and initial soil moisture.The effects on NO₃^--N transport rat were a descending order as initial soil moisture,vaporization temperature,and their interaction.The effects of initial NO₃-N contents in soil and its interactions with vaporization temperature and initial soil moisture on NO₃^--N transport rate were not significant,but it affected the absolute NO₃^--N contents of soils.After water was evaporated in soil for 5days,it showed that NO₃^--N content was higher in top layer soil and decreased with increase of soil depth,increased a little again and tended to an approximate steady value.The soil water distribution in vertical plane became low in surface layer and high in depth layer under different condition.Soil water contents decreased with increase of vaporization temperature and the soil depth to result form change of soil water gradient increased.Water contents increased after water was evaporated and soil water gradients decreased in surface layer soil with increase of soil initial water contents.Soil water contents increased with increase of soil initial NO₃^--N contents.4.Effects of moisture,temperature and nitrogen supply rate on NO₃^--N accumulation in greenhouse cultureAn incubation experiment was inducted to determined the changes of NO₃^--N accumulation with time during the process of nitrification under various soil moisture, soil temperature and nitrogen supply rate for greenhouse soil.The results indicated that equation△（NO₃^-）=e^（a+b/τ） could be used to express the NO₃-N accumulation with time. The maximal rate of nitrification,delay period and maximal NO₃^--N mass of NO₃^--N accumulation were derived from the equation,and used to characterize quantitatively the nitrification process in different soil conditions.The effects on maximal rate of nitrification were a descending order as soil moisture,soil temperature,interaction between temperature and moisture,interaction of moisture between nitrogen supply rate, and nitrogen supply rate,and which was descending order of soil moisture,soil temperature,nitrogen supply rate and interaction of moisture and nitrogen supply rate on delay period.Maximal NO₃^--N mass of accumulation depended on nitrogen supply rate, moisture and temperature,and affected no significantly by their interactions.In greenhouse production systems,where moisture and temperature could be controlled,this model could be used to predict NO₃^--N accumulation and the effectiveness of N in the fertilizer management that considers both nitrogen supply rate and soil environment.5.Effects of moisture,temperature and nitrogen supply rate on pH and electric-conductivity in greenhouse cultureThe effects of temperature（T）,moisture（W）,nitrogen supply rate（N） and their interaction on pH and electrical conductivity of soil（EC） were studied in the laboratory incubation for the greenhouse culture soils.The results indicated that pH decreased with incubation time and first-order dynamic model could be used to express reduce rate.N,W, W×N and T×W sharply effected the pH reduce rate constant（k） which was descending order of N＞W＞W×N＞T×W.EC increased quickly to the maximum in the first week in the incubation then decreased lightly,and changed in an approximate constant EC_sty at last time.N,W,T×W and T had impact on EC_sty in a highly marked level and W×N in a significant level.Soil acidification and EC increment could be controlled by reduction of nitrogen supply rate and regulated by deficit irrigation.The regression equations of k and EC_sty were found and the equations could be used to predict pH reduce and EC_sty in the fertilizer management that considers both nitrogen supply rate and soil environment.6.Sensitivity responses of soil nitrate accumulation,pH and EC to soil moisture and N application rateSoil incubation was conducted to evaluate the sensitivity responses of nitrate accumulation,pH and electrical conductivity（EC） to soil moisture and N application rate in an open field soil（clay loam） compared with the same soil that in an adjacent greenhouse.The results indicated that the additional nitrate accumulation arising from the treatments imposed,pH descending and increased EC were greater in the greenhouse soil than in the open-field soil under the same soil moisture and N application rates.The nitrate accumulation rate and pH descending rate were increased with increasing of soil moisture,and most enhanced at 90%water holding capacity in the glasshouse soil.By contrast,the nitrate accumulation and pH descending rate was greatest at 70%water holding capacity in the open field soil.The nitrate accumulation rate and pH descending rate in greenhouse soil was more sensitive to N application rate compared with that in the open field soil.Increasing soil moisture and N application rate enhanced the EC in greenhouse soil and in the open field soil.The impacts of soil moisture and N application rate on the EC increment in the open field soil were more significant than that in greenhouse soil.the EC absolute increments in greenhouse soil with incubation time were far exceed that in the open field soil,which lead to serious salinization in greenhouse soil.7.Effects of moisture and nitrogen interaction on plant nitrogen uptake in greenhouse cultureA culture experiment was conducted with the soil in which nitrate was accumulated seriously.It was advantageous to tomato growth when soil moisture was 100%FC and N application rate was 150mg/kg.In this treatment,nitrate reductase activity（NRA） of plant was higher and nitrate accumulation was lower than that in other treatments.The residual soil nitrate in this treatment was lower than that in other treatments after tomato harvest. When soil moisture was 80%FC and N application rate was 300mg/kg,growth of tomato was delayed and tomato plant becamed fugacious.Nitrate reductase activity（NRA） of tomato in this treatment was lower and nitrate accumulation was lower than that in other treatments.The residual soil NO₃^--N and NH₄⁺-N was in a high level after tomato harvest. Sufficient irrigation is more beneficial to tomato growth and nitrogen uptake than deficit irrigation for soil of nitrate accumulation seriously.8.BP Neural Network model for soil nitrate accumulation in greenhouse culture An improved BP Neural Network（BPNN） with additional momentum and adaptive learning rate was applied to set up the predictive model to interaction of moisture, temperature and nitrogen on soil nitrate accumulation in greenhouse culture.The model was designed applying Matlab 6.5 and the check samples was simulated with the designed model.The calculated precisions between BPNN model and regression model were compared.The result showed that the model was of rapid convergent speed,high precision and better fit effect.The model could be applied to forecast the interaction of moisture,temperature and nitrogen on soil nitrate accumulation in greenhouse culture.更多还原