Effects of arsenic addition in soil on soybean growth and the content of nitrogen, phosphorus and potassium in soybean plant
土壤添加亚砷酸钠对大豆生长和植株氮、磷、钾含量的影响

Arsenic (As) is toxic to plants and animals. A soil pot experiment with the arsenic addition levels of 0, 5.0, 10.0, 30.0, 50.0, 100.0 mg kg-1 was conducted to investigate the effects of soil arsenic addition on soybean growth and the content of nitrogen, phosphorus and potassium. The results showed that when soil arsenic addition was at a level of 50 mg kg-1, soybean demonstrated a series of toxic symptoms with crimple and dark green leaves, withered leaf edge, dwarfing plant and delayed maturation. The plant heights of soybean decreased with increase of soil arsenic supplement and there was significant negative, exponential correlation between the soil arsenic additions and plant heights of soybean. Soil arsenic addition of 100 mg kg-1 caused 41.5% decrease in plant height, 43.4% in total biomass and 56.1% in the yield of soybean grain. The ratio of root biomass to that of aerial parts and biomass of leaf and stem to that of aerial parts increased, while the ratio of grain biomass to that of leaf and stem, aerial parts and total biomass was decreased. These results meant that high soil arsenic addition suppressed the growth of aerial parts and grain. Soil arsenic pollution had significant effects on the content of nitrogen, phosphorus and potassium in soybean. When soil arsenic addition was 100 mg kg-1, compared to control (no arsenic addition), soybean nitrogen and phosphorus content in grains, roots and leaves and stems, potassium content in leaves and stems and in roots increased significantly, but the potassium content in grains decreased significantly, while the ratio of nitrogen, phosphorus and potassium content in soybean grains to that in leaves and stems and to that in roots decreased significantly. These implied that arsenic stress suppressed the translocation of the nitrogen, phosphorus and potassium in leaves and stems to grains. In summary, over 50.0 mg kg-1 soil arsenic addition could be toxic to soybean growth, but soybean could adapt to the arsenic polluted environment by adjusting the content of nitrogen, phosphorus and potassium in various parts. The essence of arsenic toxicity to soybean growth was to inhibit the growth of soybean aerial parts and the formation of soybean grains because of the suppression of the translocation of nitrogen, phosphorus and potassium in roots, leaves and stems to grains.