【作者】 姬景红；

【导师】 张玉龙；

【作者基本信息】 沈阳农业大学 ， 农业环境与生态， 2008， 博士

【摘要】 由于多年连作、盲目施用化肥及不合理的灌溉管理措施,保护地土壤氮素积累、硝态氮淋失以及氨态氮挥发现象严重,不但造成了肥料氮的大量浪费,同时也产生了一系列的土壤退化及环境保护问题。本文从当前生产实际出发,用保护地长期定位灌溉试验的方法,深入系统地研究渗灌、滴灌和沟灌三种灌溉方法对保护地土壤各形态氮素含量、有机氮的矿化特点以及番茄产量和植株吸氮量的影响,探讨了各灌溉处理保护地土壤的供氮能力及其供氮后效。长期定位灌溉试验于1998年开始,灌溉控制上限和下限分别设定为土壤水吸力6.3KPa和40KPa,其中渗灌和滴灌处理一次灌水量为沟灌一次灌水量的1/2;每年春季栽培一茬番茄,各小区施肥量一致,每年的试验方案、试验方法完全相同。本文供试土壤样品采自2004年秋季（连续进行灌溉试验7年）,作物样品番茄植株、果实采自2007年灌溉试验进行期间。主要研究结果如下:1.有机质、全氮及各形态氮的含量及其分布三种灌溉处理,土壤有机质、全氮含量在0～50cm层次随土层深度的增加而降低,至50cm以下其含量降到很低且基本不再随深度而发生改变。在0～20cm土层,渗灌处理土壤全氮、硝态氮、铵态氮的积累量最高,沟灌次之,滴灌最小。三种灌溉处理的各层次土壤有机氮含量占全氮的百分比大都在95%以上,只有渗灌处理0～10cm、10～20cm土层及沟灌处理0～10cm土层土壤有机氮占全氮的比例较低,分别为63.29%、77.87%及77.21%。各灌溉处理0～80cm土层内不同深度层次土壤有机态氮含量均以酸解氮为主,酸解氮中未知态氮、氨态氮、氨基酸态氮和氨基糖态氮的绝对含量和相对含量排列顺序均为未知态氮＞氨态氮＞氨基酸态氮＞氨基糖态氮。三种灌溉方法相比较,各个层次土壤酸解氮中氨基酸态氮、氨基糖态氮及氨态氮占全氮的比例,总体上滴灌和渗灌处理高于沟灌处理,而酸解未知态氮和非酸解氮占全氮的比例,沟灌处理高于滴灌和渗灌处理。2.土壤有机氮矿化特点各灌溉处理0～50cm土层内不同层次土壤有机氮的矿化过程均以Two pool模型拟合效果最佳。Two pool模型拟合得出的矿化参数表明,与渗灌和沟灌处理相比,长期采用滴灌灌溉不但有利于表层土壤中氮矿化势（N₁+N₂）的增大,也有利于易矿化有机氮（N₁）的形成,使耕层土壤有机氮的品质得到改善。三种灌溉处理中以沟灌处理最不利于土壤有机氮的矿化,但利于其积累:渗灌处理各土层土壤有机质矿化的难易程度及其数量的多少介于滴灌与沟灌处理之间。温度和湿度是影响有机氮矿化的重要因子。温度和湿度与土壤氮素矿化速率之间呈显著的正相关关系,且二者影响土壤氮素矿化速率的交互作用明显。就耕层（0～20cm土层）土壤而言,有机氮矿化的适宜温度是35℃,适宜湿度为田间持水量的83%～100%。3.有机氮组分与土壤氮矿化势之间的关系各灌溉处理0～50cm土层内不同层次土壤的氮矿化势值（N₁+N₂）与相应土层各有机氮组分含量之间关系十分密切,总体上对土壤氮矿化势贡献最大的是氨基酸态氮。但在不同灌溉处理间各种土壤有机氮组分对其氮矿化势的贡献又表现出差异;渗灌处理不同深度层次土壤的氮矿化势与酸解氨基酸态氮和氨基糖态氮,滴灌处理与未知态氮,沟灌处理则与酸解氨基酸态氮、未知态氮含量关系密切。4.土壤供氮能力的全面评价由于不同灌溉处理各层次土壤中初始矿质态氮含量较高,因此,评价土壤供氮能力时就必须考虑这一部分氮素对土壤供氮能力的影响。本文以土壤起始无机态氮量（NH₄⁺-N+N0₃^--N）与氮矿化势（N₁+N₂）二者之和作为土壤供氮能力指标。0～40cm土层土壤供氮能力明显高于其下层土壤。0～20cm土层土壤供氮能力以渗灌最强,沟灌其次,滴灌最小;20～30cm土层以沟灌最大,滴灌其次,渗灌最小。2007年测定番茄产量、生物量及植株吸氮量,结果表明滴灌处理番茄植株总生物量高于渗灌和沟灌处理,表现出增产、能够促进果实氮素吸收的效果。说明滴灌处理比沟灌和渗灌处理土壤供氮持久稳定。上述土壤氮素含量分布、形态组成及有机氮矿化特征是由于不同灌溉方法灌溉其水分含量剖面不同,导致土壤的热状况、通气状况不同造成的。水、气、热条件不同,既影响到土壤有机质的矿化分解,致使土壤有机质（氮）质量发生改变,又使土壤中水盐运动方向、数量相异,使无机态氮及一些低分子量的有机氮不断地进行着重新分配。试验过程中0～20cm土层水分含量观测结果表明,沟灌经历着全面湿润、全面干燥过程,渗灌经历的是相对干燥而且较为稳定的过程,而滴灌即使灌水后也总是处于部分湿润、部分相对干燥状态,这是造成不同灌溉方法灌溉多年后土壤氮素肥力特征不同的直接原因。总之,就现有灌水技术而言,从农业节水、提高氮肥利用率及防止土壤退化方面综合考虑,保护地长期使用滴灌灌水效果最佳。长期使用渗灌灌溉应注意防止盐分积累,并可以适量减少氮肥的用量。而沟灌灌溉不但浪费水源,同时降低氮肥利用率,进而影响着番茄产量的提高。本文首次对长期定位灌溉试验的保护地土壤供氮特性进行了研究,其结果丰富了我国保护地土壤氮素研究理论,对于保护地蔬菜栽培合理地进行水肥管理,防止土壤退化具有重要的理论与实际意义。更多还原

【Abstract】 Soil N accumulation, nitrate leaching and ammonia volatilization were serious in protected field because of planting the same vegetable for many years, applying fertilizer and irrigation management measures unreasonably, which not only caused a lot of N fertilizer waste, but also had a series of soil degradation and environmental protection problems. According to the current actual situation, different irrigations were used in the protected field. The effect of different irrigation methods on N content, the mineralization of organic N, tomato yield and N absorption of plant were studied; N supplying capacity and N durative effect of protected field soil were discussed by chemical extraction and biological incubation methods. The experimentation began in 1998, and irrigation control upper and lower limits were seted to soil water suction for 6.3 KPa and 40 KPa. The water quantity of furrow irrigation was half of subsurface irrigation and drip irrigation’s every time; tomato was cultivated in annual spring, fertilization amount was same in different plots, annual test scheme and test methods were exactly same. Soil samples were collected in the fall of 2004, the tomato fruit and plants were harvested in 2007 for the study. The results were showed as follows:1. The content and distribution of soil organic matter and total NAt 0～50 cm layers, the content soil organic matter and total N were decreased with layers’ depth. At 0～20 cm layers, subsurface irrigation was advantage to accumulate soil total N, nitrate N and ammonium N, and furrow irrigation was secondly, drip irrigation was the smallest.At all layer levels, the percentage of soil organic N to total N was more than 95%, while soil inorganic N was generally less than 5% under three irrigation treatments. But the proportion of soil organic N to total N was lower at 0～10 cm , 10～20 cm of subsurface irrigation and 0～10 cm of furrow irrigation, the content were respectively 63.29%, 77.87 % and 77.21%.At 0～80 cm layers, acidic hydrolysable N was the main components of the organic N, the order of the content of Acidic hydrolysable N forms and the proportion to total N were unknown N>ammonia N>amino acid N>amino sugar N. Compared with three irrigation methods, except for a few layers, the proportion of amino acid N, amino sugar N and ammonia N to total N in various layers of drip irrigation and subsurface irrigation were higher than furrow irrigation; but the proportion of unknown N and Non-acidic hydrolysable N to total N of furrow irrigation were higher than drip irrigation and subsurface irrigation.2. The characteristics of soil organic N mineralizationTwo-pool model was fitted to describe the process of organic N mineralization, and it was optimal. N mineralization parameters showed that drip irrigation treatment not only could increase N mineralization potential but also could promote active organic N amount. For the three irrigation methods, furrow irrigation was advantage to accumulate organic N, drip irrigation could improve the quality of soil organic N and increase the capacity of organic N mineralization at 0～20 cm layers. organic N mineralization of subsurface irrigation was higher than furrow irrigation’ and lower than drip irrigation’.Temperature and moisture were important factors to organic N mineralization. There had significant positive correlation between N mineralization rate and temperature or moisture, and had a significant interaction. At 0～20 cm layers, temperature of 35℃and the water content of 83% to 100% field capacity were appropriate temperature and moisture levels for protected field soil.3. The relationship between organic N forms and N mineralization potential, soil N supplying capacityAt 0～50 cm layers, there had closely relationship between organic N forms and N mineralization potential. Amino acid N had important contribution to mineralized N. The source of N mineralization potential was different under different irrigation treatments. For subsurface irrigation, N mineralization potential and amino acid N and amino sugar N had a close relationship; for drip irrigation, N mineralization potential was correlative to unknown N, while furrow irrigation, N mineralization potential was closely correlative to amino acid N and unknown N.4. A comprehensive evaluation for soil N supplying capacityThe content of initial mineral N was high at various layers under different irrigation methods, so this part of inorganic nitrogen must be considered in evaluation of soil nitrogen supplying capacity. The sum of initial inorganic nitrogen in the soil and nitrogen mineralization potential was considered as index of soil nitrogen supplying capacity. At 0～40 cm layers, soil N supplying capacity was stronger in protected field. At 0～20 cm layers, subsurface irrigation treatment had the largest soil N supplying capacity, furrow irrigation was Secondly, drip irrigation was the smallest under Long-term different irrigation treatments. At 20～30 cm layers, the order of soil N supplying capacity was furrow irrigation>drip irrigation>subsurface irrigation.Tomato production, biomass and plant N absorption was measured in 2007. The result showed that dry matter weight under drip irrigation was more than subsurface irrigation’s and furrow irrigation’s; Tomato yield and N absorption of fruit were increased under drip irrigation treament. The process of soil N supply had lasting stability under drip irrigation than furrow irrigation and subsurface irrigation.The difference of content, distribution, composition of Soil N and characteristics of organic N mineralization were due to the difference of distribution of soil water, the temperature, the pore of soil under different irrigation methods. Different water, gas, heat conditions affected not only the decomposition of soil organic matter but also the movement of salinity. So that inorganic N and some of low molecular organic N were continuously re-allocated. At 0～20 cm layers, furrow irrigation had a total moist, full drying process; subsurface irrigation was relatively dry and stable process, and drip irrigation was always in part of moist, relatively dry state, which were the direct causes for the difference of soil fertility characteristics.In short, according to irrigation technology, drip irrigation was best for protect field soil in saving water, improving the utilization of N and preventing soil degradation. We should be pay attention to preventing salt accumulation, and reducing the amount of applying nitrogen fertilizer under long-term subsurface irrigation. Irrigation water was wasted, the utilization of N fertilizer and tomato production were decreased under furrow irrigation treatment.N mineralization characteristics of protected field soil under long-term irrigation were discussed firstly. The results enriched the theoretical study of protect field soil N, and had great theoretical and practical significance for optimizing water and fertilizer management and preventing soil degradation.更多还原