| Interaction exits commonly in soil -plant system. When the effect of a factor was relating to another factor, we could say there was interaction in them. There were two kinds of interactions, one is Antagonism, the other is Synergism. Antagonism means the effect of two or more than two elements to the experiment indicators is smaller than their whole results of respective effect. Synergism means the effect of interaction to experiment indicators was bigger than the whole results of respective effect. Interaction has a great significance not only in the substance circulation in soil "plant system, but also in the substance balance in soil "plant system. Cadmium (Cd) is a toxic element. The background value of Cd in soil is from 0.01 mg/kg to 2 mg/kg, the average is 0.35 mg/kg. Cd is poisonous for animals, plants and human beings. In 1960't, the inhabitant in FUSHAN County in Japan ate the Cd rice, their health were greatly influenced by "Itai Itai Disease". The bone of patient turned soft, some of them even died. After that, the behavior of Cd hit the attention of scientists of environment protection. They have done much scientific research on it. The Cd in soil came from waster water, gas, slag and the use of sludge. The content of Cd in metallurgical dust from smeltery is nearly 2300 mg/kg, the content of Cd in waste water from smeltery is several mgIL. The slag also emitted Cd ion. In addition, waste water irrigation was another important cause of Cd pollution. The statistics showed that today the area of waste water irrigation was 1,300,000 hm2 in China. It caused heavy metal pollution in field land. And the main factors were Cadmium and Mercury. Phosphorus is necessary element to all plant. It was not only components of plant organ, but also taking part in soil plant animal system. In the past, two strategies have been raised to deal with Cd polluted soil. One is to exchange the surface soil, the other is to add improvement agent. In recent years, scientists were interested in using fertilizer to control plant assimilating heavy metals. In most of previous research, people paid attention to compare assimilation of heavy metal by using different fertilizer. Some studied on interaction of fertilizer and several elements. There were a few reports on interaction of heavy metal and nutrient element. This research studied on interaction of Cadmium and Phosphorus . And try to explain the mechanism of interaction from soil science. In this experiment, three typical soil samples with distinct physiochemical properties were used. They were acidification purple soil, neutral purple soil and calcareous purple soil. Lettuce (Latuca Sativa L.) and swamp cabbage (Ipomoea aquatica F.) was used as test plant. This research consists of three parts. Pot experiments were adopted to elucidate the effect of interaction on different soil and different plant in part one. Distribution of Cd fractions was tested to elucidate the effect of P addition on Cd fractions in part two. In part three, absorption and desorption experiments were conducted and the mechanism was discussed. The first experiment has been done to study the effect of interaction on lettuce on neutral purple soil. Lettuce planted on soil at six levels of Cd(0. 1 3. 5. 10 30mg/kg) and four levels ofP(0 50 100. 200mg/kg). It used completely design and the sum of treatments was 24. The second pot experiment has been done to study the effect of interaction o... |
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