Effect of phosphogypsum on nutrient balance and membrane defense enzyme of broomcorn in strongly acidic soils

Pot culture trials were conducted to probe into the effects of phosphogypsum on growth, nutrient balance and membrane defense enzyme of broomcorn in strongly acidic yellow soils. Results show that the broomcorn seedlings do not grow well without application of phosphogypsum or lime, even under sufficient nutrient supply. However, the seedlings grow normally after application of phosphogypsum or lime, which increases soil pH and at the same time decreases exchangeable Al concentration in strongly acidic soils. There is significantly quadratic correlation between seedling dry-weight (Yw) and phosphogypsum (X₁) or lime (X₂) dose. Regression equations for the relations are: Yw = 6.88+11.92 X₁-1.65 X₁^{2sup, R = 0.983**; Yw= 6.88+6.39X₂-0.72X₂2, R= 0.996**. Lime is superior to phosphogypsum in alleviating A1 toxicity and raising calcium content. But it is inferior to phosphogypsum in increasing available nitrogen, phosphorus and potassium in broomcorn seedling. After phosphogypsum application, phosphorus content in broomcorn seedling is 1.17~2.43 times that in lime treatment. Compared with lime treatment, phosphogypsum application increases nitrogen, phosphorus, potassium and calcium contents while sustaining moderate levels of N/P, N/K and K/P. This improves the balance between nitrogen, phosphorus, potassium and calcium in broomcorn plant. Phosphogypsum is superior to lime with regards increased activity of superoxide dismutase (SOD) and catalase (CAT), and decreased activity of peroxidase (POD) and proline content (Pro) in the leaves of broomcorn. Phosphogypsum could therefore be regarded as a strongly acidic soil ameliorant that is superior to lime.}