【作者】 胡坤；

【导师】 涂仕华； 王昌全；

【作者基本信息】 四川农业大学 ， 植物营养学， 2010， 硕士

【摘要】 随着社会经济的快速发展,人类生存环境承受了前所未有的污染压力。在众多污染元素中,重金属镉(Cd)污染最具典型性,受Cd污染的土地面积和农产品(如水稻、小麦)Cd超标的数量远高于其他有害元素,四川省的情况也不例外。土壤一旦被Cd污染,其治理难度之大,治理时间之长,治理代价之高,通常超出常人的想象。在农业生产中,不良的土地利用方式、农耕农作模式、农田管理、特别是肥料品种和施用方法不当时,往往会显著提高土壤Cd的有效性和作物吸收量,增加农产品Cd超标的几率。因此,开展Cd污染土壤上影响土壤Cd有效性的变化因子及其调控措施,特别是不同肥料对Cd有效性的影响与作物吸收,对我国的食品安全和人类健康,意义重大。施用肥料会影响土壤的某些理化性状,从而影响土壤镉的形态变化及植物对镉的吸收和积累。在过去的研究中,国内外作者已对一些中、微量元素和有益元素如Ca、Zn、Si、Se进行了研究,但在同一条件下中、微量元素和有益元素对土壤重金属生物有效性影响的系统比较的研究鲜见报道。因此,本试验旨在系统研究不同中微量及有益元素对土壤镉有效性的影响及其对水稻生长和吸收镉的影响。本研究采用土壤室内培养试验研究了淹水条件下不同中微量及有益元素肥料对土壤镉有效性的影响,采用网室盆栽试验研究了淹水条件下不同中微量及有益元素肥料对水稻生长及吸收镉的影响和不同水分管理方式下三种中微量元素肥料对水稻生长和吸收Cd的影响,在此基础上初步提出了水稻优化施肥技术。本试验取得的主要研究结果如下：1.淹水培养试验结果表明,不同中微量元素和有益元素对土壤pH和Cd有效性的影响存在显著差异。淹水后,土壤pH由6.4迅速上升至7.0,维持一段时间后缓慢回落,60d时降至6.7；土壤Cd的有效性经历了与pH相反的变化过程。Ca2+、Mg2+、S、硅酸钠和碳酸钙等能显著降低土壤中有效Cd含量,而Zn2+、Cu2+和Fe3+能显著增加土壤有效Cd含量。因此,建议在镉污染土壤上种植水稻时,在选择中微量元素及有益元素肥料时,宜施用碳酸钙、硅酸钠和含硫肥料,慎重使用铜肥和锌肥。如果必须施用这些元素时,应把用量控制在生产推荐量以下。2.盆栽土培试验表明,在所有测试的元素和施用方法中,硅酸钠叶面喷施显著增加稻谷产量,而碳酸钙、硼酸、硅酸钠土施和亚硒酸钠显著降低了稻谷产量。镁、锌、铁的盐酸盐形态对水稻籽粒的增产效果优于硫酸盐形态,而钙、铜的硫酸盐形态增产效果略高于盐酸盐形态。在钙、镁、硫三种中量元素中,钙增加了水稻籽粒中的Cd浓度和吸收量,而镁和硫则降低了籽粒中的Cd浓度和吸收量,以硫磺粉处理为最低。稻草中的Cd浓度和总量均以氯化镁处理为最高,硫磺粉处理最低。镁能有效抑制Cd从秸秆向籽粒的转移,其盐酸盐优于硫酸盐。在微量元素中,锌对水稻Cd的吸收抑制作用最为显著,其次是铜,而有益元素肥料硅酸钠叶面喷施则显著增加了稻谷中的Cd浓度和吸收量。硫酸亚铁、氯化锰、氯化铜、硼酸和硼砂处理都能有效地抑制Cd从秸秆向籽粒的转移,而硅酸钠叶面喷施和锌处理则促进了Cd的转移。在Cd污染土壤上选用适宜的中微量和有益元素肥料及其施用方法,能有效降低水稻对镉的吸收和稻米中的Cd含量。3.不同水分管理方式下S、Fe、Zn盆栽试验研究表明,在三种水分管理方式中,晒田水稻产量最高,其次为淹水,最低为湿润灌溉。淹水处理比湿润灌溉显著降低了水稻籽粒中的Cd浓度,其中以Zn处理最为显著。淹水处理明显抑制了Cd从秸秆向籽粒的转移,与之相反,湿润灌溉处理促进了Cd从秸秆向籽粒的转移。因此,在Cd污染土壤上,水稻栽培应尽量采用全生育期淹水的水分管理方式,污染程度较轻的稻田亦可考虑在灌浆期进行晒田,但不宜水稻旱作。采用Cd抗性品种,结合优化的肥、水管理措施,可以使稻米中Cd含量低于国家无公害大米的限量指标。更多还原

【Abstract】 With rapid development in social and economics, the living environment of human being is facing the unprecedented pressures from various types of pollution. Among the different pollutants, cadmium (Cd) is typical for its widespread pollution areas and higher number of suffered agricultural produces (eg., rice and wheat) than the other risky elements. Once the soil is polluted by Cd, it is very difficult to remediate due to time-consuming and high cost of the recovering processes that are beyond imagination of the ordinary people. In the agricultural production, improper land use, crop cultivation, farmland management and sources of fertilizers and application methods in particular tend to significantly enhance availability of soil Cd and crop uptake, leading to higher probability of polluted agricultural produces. Therefore, it is of great importance to conduct research on the factors that can reduce quantity of soil available Cd and the measures that can control soil Cd availability to safeguard food safety and human health.Past research on some of the secondary, micro-and beneficial elements has been conducted both at home and abroad, however, there is lack of systematic studies with comparisons between different secondary, micro-and beneficial elements affecting the availability of soil Cd under the same conditions. Thus, the objectives of this study were to systematically investigate effects of secondary, micro-and beneficial elements on availability of soil Cd and Cd uptake by rice under waterlogged condition. The availability of soil Cd and Cd uptake by rice as affected by different secondary, micro-and beneficial elements were investigated by incubation studies and pot experiments under waterlogged condition as well, The availability of soil Cd and Cd uptake by rice as effects of water management methods and three secondary and microelements were investigated by incubation studies and pot experiments.On the basis of these studies, some optimized fertilizer practices that are effective in controlling Cd availability on the Cd polluted soil were concluded.1. The results of incubation experiments revealed that different fertilizers significantly affected soil pH and Cd availability. As the soil was flooded, soil pH rose rapidly from 6.4 to 7.0, maintained for a period of time and then dropped down to 6.7 at 60d, while the soil Cd availability underwent a reverse change. Ca2+, Mg2+, S, sodium silicate and calcium carbonate were highly effective in reducing amounts of Cd extracted, while the micro-elements of Zn2+, Cu2+ and Fe3+ significantly increased the extractable Cd. Thus, the authors suggest that when making fertilizer recommendations of secondary, micro-and beneficial elements to the Cd polluted soils in rice growing season, sodium silicate and S bearing materials are most preferred while use of Cu and Zn should be cautious by strictly controlling its rates following recommendations.2. The results of soil pot experiments revealed that folia application of sodium silicate significantly increased rice grain yield, while calcium carbonate, boric acid and sodium silicate incorporated into soil significantly reduced rice grain yield. The chloride forms of magnesium (Mg), zinc (Zn) and iron (Fe) were more favorable to enhance rice grain yield than the sulfate salts of the three elements, while the sulfate forms of calcium (Ca) and cupper (Cu) just behaved in an opposite manner. Among the three secondary elements of Ca, Mg and sulfur (S), Ca enhanced but Mg and S in particular reduced the concentrations and uptake of Cd in grain. In straw, the concentrations and uptake of Cd were minimized by magnesium chloride and S in particular. It was found that Mg retarded transferring Cd from straw to grain, with magnesium chloride more effective than the magnesium sulfate. Among the micro-elements studied, Zn was most effective in blocking Cd uptake by rice, and followed by Cu, while folia application of the beneficial element of Si as sodium silicate topped the all the treatments in concentrations and uptake of Cd in grain. The treatments of ferrous sulfate, magnesium chloride, cupper chloride, boric acid and borax effectively depressed but the treatments of Zn and folia application of sodium silicate promoted the transfer of Cd from straw to grain, indicating the mechanism of Si blocking Cd uptake by rice was most likely to occur in soil rather than within plant or in the aboveground portions of the plant. It implies that selecting appropriate forms of secondary, micro-and beneficial elements and using proper application methods could effectively reduce Cd uptake by and Cd content in grain in the Cd polluted soil.3. Effects of water management methods and S、Fe、Zn elements in a pot experiment revealed that among the three water management methods, water drained out at maximal tillering stage (drain-out) produced the highest rice yield, and followed by flooding through the rice growing season (flooding) and non-flooding at all (non-flooding). The flooding management significantly reduced Cd concentration and total content, especially in the Zn treatment, in grain compared to the non-flooding management, and effectively inhibited transfer of Cd from rice straw to grain. On contrary, the non-flooding management promoted Cd transfer. Thus, it is suggested that flooding water management should be used all time when possible for rice grown on a Cd polluted soil, the drain-out management can be adopted on soils with slight Cd pollution, and non-flooding management should avoided as possible. Use of Cd-resistant rice cultivars in combination with optimized nutrient and water management practices can produce rice product containing Cd below the permit levels by the state.更多还原