Cycling and balance of zinc in farmland ecosystem of the Jiang-Han Plain in Hubei Province

Two years field experiments with eight cropping systems including wheat-rice， rice-rice，rape-soybean，rape-peanut，wheat-sesame，wheat-cotton，pepper-cabbage，radish-eggplant were carried out to study zinc cycling and balance of farmland ecosystem for Jiang-Han Plain in Hubei Province．The results show that the input way and the amount of zinc in proper order in different type ecosystems are as follows：for vegetable and paddy fields，organic fertilizer>rainfall>natural return>irrigation>seeds(seedlings)and for upland fields，rainfall>organic fertilizer>natural return> irrigation>seeds (seedlings)．The main output of zinc is crop harvest，which ranges from 96％ to 97．6％ with a mean value of 96．7％，while field runoff and soil body leaching are very little．There are more zinc surplus in vegetable and one paddy field because of more organic fertilizer input，two of four upland field has more zinc surplus because of more organic and zinc fertilizer input together，another paddy and the other uplands are deficient in zinc because of less organic and no zinc fertilizer input．