有机质含量对石灰性黄潮土和砂姜黑土磷吸附-解吸特性的影响

Effects of soil organic matter on characteristics of phosphorus adsorption and desorption in calcareous yellow fluvo-aquic soil and lime concretion black soil

通过向土壤中添加不同量小麦秸秆,经好气培养1年后,获得不同有机质含量梯度的系列土壤,研究有机质含量对石灰性黄潮土和砂姜黑土磷(P)相关吸附参数和不同水土比下解吸溶液P浓度的影响。结果表明,Langmuir方程能够较好地拟合不同有机质含量的两种土壤对P的等温吸附曲线,拟合度达到显著(P<0.05)或极显著(P<0.01)水平。黄潮土和砂姜黑土P最大吸附量(Xm)、吸附亲和力常数(K)、最大缓冲容量(MBC)、吸附饱和度(DPS)及相同水土比下P解吸溶液浓度与有机碳含量间均呈显著或极显著的二次抛物线关系。抛物线拐点之前,随有机质含量的提高,P的吸附能力增强,解吸能力降低;拐点之后,吸附能力降低,解吸能力增强。各水土比条件下,P解吸溶液浓度与Xm、K、MBC呈显著或极显著负相关,与DPS呈显著或极显著正相关。随有机质含量的提高,土壤磷的植物有效性和P流失风险呈先降低后增强的抛物线趋势;土壤供P缓冲能力则先增强后降低。砂姜黑土Xm、K、MBC均明显高于黄潮土,DPS明显低于黄潮土;且其抛物线拐点滞后,拐点横坐标有机碳含量明显高于黄潮土。不同有机质含量的解吸曲线较黄潮土排列紧密;砂姜黑土粘粒含量、碳酸钙含量明显高于黄潮土,全P和Olsen-P含量明显低于黄潮土,这可能是造成两种石灰性土壤P吸附-解吸特性差别的主要原因。

By means of adding different amounts of wheat straw into soils, the soil samples were collected after one whole year＇s indoor incubation to study effects of soil organic matter （SOM） contents on parameters of phosphorus （P） adsorption and desorption at different soil/water ratios in the calcareous yellow fluvo-aquic soil and lime concretion black soil. Langmuir equations can be used to simulate P adsorption isotherms of the two soils with a series of different SOM contents at the significant levels. For the two soils, the quadratic parabolic curves could well describe the relationships between SOM content and maximum P adsorption capacity （Xm）, constant of P adsorption bonding energy （K）, maximum buffering capacities （MBC）, degree of P adsorption saturation （DPS） and desorbed P concentration at the same soil/water ratio. Before the inflexion of the P adsorption parabolic curve, the P adsorption performance is strengthened, and desorption performance is weakened gradually with increase of SOM content, while the reverse phenomenon occur after the inflexion of the parabolic curve. For each type of soil with a series of SOM contents, the desorbed P concentration has negative correlation with Xm, K and MBC, and positive correlation with DPS at each water/soil ratio. With the increase of SOM contents, soil P bioavailability, loss risk and buffering sorption and desorption characteristics at different soil/water capacity are effectively modulated by the changes of P adratios. Compared with yellow fluvo-aquic soil, lime concretion black soil has higher clay, calcium carbonate and lower TP, Olsen-P contents, therefore the inflexions of Xm, K, MBC and SOM curves of lime concretion black soil are obviously higher than those of yellow fluvo-aquic soil, while that of DPS of lime concretion black soil is lower.