The effects of biochar addition on the physicochemical properties of coastal saline soil and the activity of the antioxidation system in maize seedlings were studied by pot experiment

and the typical coastal saline soil sampled from Yellow River Delta was taken as test soil. A total of six treatments were set up in the experiment

including non-fertilizing (CK)

fertilizing without biochar (CFK) and fertilizing with different addition rates of biochar (the addition rate was 12.5

25.0

50.0 and 100 g/kg

respectively). The results showed that:(1) Compared with CK

with the increasing of biochar-addition rate

the electrical conductivity (EC)

available potassium

available phosphorus

cation exchange capacity (CEC) and easily oxidized organic carbon (EOC) of coastal saline soil increased significantly. The pH and alkali hydrolysable nitrogen content of soil treated with biochar showed decreased trends compared with CK

but there was no significant different between the biochar treatments. However

biochar addition had no significant effect on exchangeable sodium compared with CK.(2) Moderate addition rate of biochar (12.5

25.0 and 50.0 g/kg) increased the activities of antioxidant enzymes (SOD

POD and CAT) and root activity in maize seedlings

and reduced the production rate of superoxide anion and hydrogen peroxide content of leaves

thereby improving the physiological characteristics of maize seedlings. However

the higher addition rate of biochar (100 g/kg) exhibited a negative impact on the activity of antioxidant enzyme in maize seedlings

resulting in the higher accumulation of reactive oxygen in the plants. Therefore

moderate addition rate of biochar could improve the physical and chemical properties of coastal saline soil

and to a certain extent

effectively improve the physiological characteristics of maize seedlings under salt stress

but the higher addition rate could inhibit the antioxidant system of crops.