Effects Of Combined Application Of Cow Manure And Straw On Cadmium Uptake And Antioxidant Enzymatic Activities In Maize

In recent years,the problem of heavy metal cadmium(Cd)pollution in soils in China has become increasingly serious,how to regulate the soil contaminated by heavy metals to reduce the uptake of Cd by crops has become a research hotspot in the fields of environmental science and soil science.With the development of agriculture and animal husbandry,a large number of crop straws and livestock manure are disposed of at will,which not only causes waste of resources,but also brings serious environmental pollution.In this study,brown soil contaminated by Cd was used as the test soil.Pot experiment was conducted to study the effects of cow manure and straw(the nitrogen ratio of cow manure to straw being 1:1,3:1,5:1)on Cd uptake,subcellular distribution and chemical fraction of various parts of maize.At the same time,the effects of antioxidant enzyme activities on the combined application of cow manure and straw were discussed,which provided a theoretical basis for the safe production of Cd contaminated farmland maize.The main findings are as follows:(1)Compared to no cow manure and staw addition,the combination of cow manure and straw significantly reduced the uptake and transport of Cd in various parts of maize,so that Cd mainly accumulated in the roots and stems of maize,reduced the content of Cd in maize grains,and decreased the toxicity of Cd on edible parts of maize.When the treatment with a nitrogen ratio of cow manure to straw being 1:1,the coefficient of Cd transported from the roots of the maize to the stems and leaves and from the stems and leaves to the grains was the lowest,0.500 and 0.004 respectively.(2)The Cd content of subcellular distribution in various parts of maize showed cell wall > organelle > soluble fraction in all treatments;the ratio of Cd in the cell wall of maize roots,leaves,stems and grains was the highest in the treatment with a nitrogen ratio of cow manure to straw being 1:1,which was 16.5%,10.5%,10.7% and 19.3% higher than that of no cow manure and staw addition.The Cd content in the ethanol extracted state of maize roots was the lowest,and the Cd content in the acetic acid extracted state was the highest.(3)Compared to no cow manure and staw addition,the content of malondialdehyde in roots,stems,leaves and grains of treatment with a nitrogen ratio of cow manure to straw being 1:1 was the lowest,33.68,0.85,5.70 and 4.74 ?mol·g-1,respectively,and the activities of superoxide dismutase,peroxidase and catalase were the lowest in all parts of maize.It indicated that the content of active oxygen and peroxide in the various parts of maize under this treatment was the lowest,and the degree of Cd stress was the least.Therefore,under the treatment with a nitrogen ratio of cow manure to straw being 1:1,the uptake of Cd in all parts of maize was the least,and the tolerance of Cd was the strongest in maize,which was the best in agricultural production and food safety.