| More accumulatation of Cd in soil caused by unreasonable actions results inover-standard Cd concentration in vegetable, even polluts food chains, and thenendangers our health. But Zn is an essential microelement for vegetable growth. In thisthesis, spinach and amaranthanus as plant materials were applied to study the effect ofdifferent form of N fertilizer (ammonium and nitrate) and its ratios (NH4/NO3, %/%) onsoil pH, vegetable yield and quality, soil Cd and Zn forms and bioavailability. Twofactors, i.e. Cd levels and N forms were designed for Experiment 1; two factors, i.e. Cdlevels and ammonium and nitrate ratios (NH4/NO3, %/%) were designed for Experiment2; three factors, i.e. Cd levels and ammonium and nitrate ratios (NH4/NO3, %/%) andZn levels were designed for Experiment 3. The main result are outlined as following:1. Fresh weight of spinach or amaranthanus reduced with the increase of Cdconcentration in soil, indicating that high Cd concentration restrained growth of spinachor amaranthanus. Compared to no Cd added soil, the highest Cd concentration(5mg.kg-1) in soil reduced fresh weight of spinach and amaranthanus by 30.7-90.5%,6.5-11.5%.and 26.4-39.4% for experimental 1, 2 and 3, respectively. Applied NO3--N canaccelerate the growth of spinach or amaranthanus. Fresh weight of spinach was thegreatest when applied only NO3—N. Fresh weight of amaranthanus was greatest whenNH4/NO3 ratio was 25/75, but fresh weight in only NO3—N treatment was lower thanthat of 25/75 ratio for NH4/NO3. In addition, added appropriate Zn can also increasefresh weight of spinach.2. Nitrate content in spinach and amaranthanus increased with increased NO3--Nproportion. But added Zn (20mg.kg-1) treatment reduced the nitrate accumulation in spinach.3. Different NH4/NO3 ratio affected Vc content in vegetable to some extent. Vccontent of spinach in only NO3--N treatment was higher than that of only NH4+-Ntreatment.4. Different NH4/NO3 ratio influencd soil pH obviously. Compared to only NH4+-Ntreatment, only NO3--N treatment increased 0.23-0.36, 0.84～0.99, 1.38～1.80 pH unit forexperimeantal 1, 2 and 3, respectively.5. Soil pH is an important factor affecting soil Cd and Zn forms and bioavailability.With the enhancement of NO3--N proportion, soil pH increased, contents of watersoluble and exchangeable Cd and Zn in soil and absorption of Cd and Zn by plant(spinach and amaranthanus) reduced significantly, but carbonate bond-Cd andcarbonate bond-Zn increased.6. With increased Cd (Zn) concentration in soil, Cd (Zn) uptake increased obviously.When Cd and Zn coexisted, Zn (Cd) uptake decreased with the increasing of Cd (Zn)concentration, indicating that there were significant antagonism between Cd and Zn.Therefore, selecting appropriate fertilizer form can affect the form andbioavailability of soil Cd and Zn, and then reduce Cd pollution and increase Znabsorption, so as to insure nutrition and safety of agricultural products.
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