生物炭与氮肥配施对高粱生长及镉吸收的影响

为探讨生物炭与氮肥配施对高粱生长及镉(Cd)吸收的影响,采用盆栽试验,研究了在中、轻度Cd污染土壤(以YB1、YB2表示)上分别进行0、2%和5%3个生物炭用量(以B0、B2、B5表示)配施0、200、500 mg·kg~(-1)3个施氮水平(以N0、N200、N500表示)对土壤理化性质、有效Cd含量、高粱光合特性及其Cd吸收的影响。结果表明:两种土壤上,增加生物炭用量能提高土壤pH和有机质含量,并在5%添加量时显著降低土壤CaCl_2-Cd含量;氮肥水平仅在YB1土壤上显著影响土壤CaCl_2-Cd含量。YB1土壤上,氮肥水平对高粱净光合速率、气孔导度和蒸腾速率有显著影响,均有随施氮量增加而增加的趋势;而高粱地上部Cd含量与CaCl_2-Cd含量显著正相关,在B5N0处理中最低(3.87 mg·kg~(-1)),B0N200处理中最高(6.79 mg·kg~(-1))。YB2土壤上,生物炭用量对高粱净光合速率、气孔导度、胞间CO2浓度和蒸腾速率均有极显著影响,气孔导度和蒸腾速率有随生物炭用量增加而降低的趋势;高粱地上部Cd含量与气孔导度、蒸腾速率显著正相关,与生物量显著负相关,在B2N500处理中最低(3.79 mg·kg~(-1)),B0N0处理中最高(5.32 mg·kg~(-1))。研究表明,生物炭与氮肥配施能影响土壤理化性质、高粱光合特性和生长等因素,进而影响高粱地上部对Cd的吸收,不同土壤条件下影响高粱地上部Cd吸收的主要因素存在差异。

Effects of simultaneous biochar and nitrogen fertilizer application on the photosynthesis and Cd uptake of sorghum

To investigate the effects of simultaneous biochar and nitrogen fertilizer application on soil properties and on the photosynthesis and Cd uptake of sorghum, two soils(YB1 and YB2), which possessed different levels of Cd pollution, were treated with either 0, 2%, or 5% biochar (B₀, B₂, and B₅, respectively)and with either 0, 200 mg·kg^-1, or 500 mg·kg^-1 nitrogen fertilizer(N₀, N₂₀₀, and N₅₀₀, respectively). The results showed that the highest biochar rate(5%)significantly increased soil pH and organic matter content and significantly reduced CaCl₂-Cd content, regardless of soil type. Meanwhile, nitrogen fertilizer application only exerted significant effects on the CaCl 2-Cd content of soil YB1. Nitrogen fertilizer application also significantly affected net photosynthetic rate, stomatal conductance, and transpiration rate, all of which increased with increasing nitrogen fertilizer application rate in soil YB1. In addition, the Cd concentration of sorghum shoots was positively correlated with the CaCl₂-Cd content of soil YB1, and the lowest Cd content(3.87 mg·kg^-1)was observed in the B₅N₀ treatment, whereas the highest content(6.79 mg·kg^-1)was observed in the B₀N₂₀₀ treatment. For soil YB2, net photosynthetic rate, stomatal conductance, intercellular CO₂ concentration, and transpiration rate were significantly affected by biochar application rate. However, stomatal conductance and transpiration rate decreased with increasing biochar rate. Moreover, the Cd concentrations of sorghum shoots grown in soil YB2 were positively correlated with stomatal conductance and transpiration rate and were negatively correlated with aboveground biomass, and the lowest Cd content(3.79 mg·kg^-1)was observed in the B₂N₅₀₀ treatment, whereas the highest content(5.32 mg·kg^-1)was observed in the B₀N₀ treatment. Therefore, simultaneous biochar and nitrogen fertilizer application affect the Cd accumulation of sorghum shoots by influencing soil properties, photosynthetic characteristics, and aboveground biomass. However, Cd uptake is also affected by soil type.