不同类型水稻土对氮磷养分的吸附解吸特征研究

Adsorption and Desorption Characteristics of Nitrogen and Phosphorus in Paddy Soils from Different Parent Materials

为探明不同母质发育的稻田土对氮、磷养分的吸附解吸特征,以湖南省主要稻田土壤红黄泥(HH)、河沙泥(HS)、麻沙泥(MS)和紫色土(ZS)为对象,研究了不同母质发育的稻田土壤对氮、磷的吸附与解吸行为。结果表明:在低氮浓度范围内(0~10 mg/L),土壤氮解吸量大于吸附量;高浓度范围(20~50 mg/L),随着平衡液氮浓度的增加,土壤氮解吸率逐渐降低;当土壤氮吸附量为-57.267~352.400 mg/kg时,不同母质发育的稻田土氮吸附能力降序排列为HS>ZS>HH>MS;当氮解吸量为8.367~37.833 mg/kg时,不同母质发育的稻田土氮解吸能力降序排列为HH>HS>MS>ZS;4种土壤对氮的吸附等温曲线用Linear模型能较好拟合,相关系数在0.928~0.978之间。而在低磷浓度范围内(0~10 mg/L),土壤磷吸附量大于解吸量;当平衡液磷浓度超过10 mg/L时,土壤固持磷的能力减弱,解吸增加,但吸附量仍大于解吸量;当土壤磷吸附量为-110.312~534.961 mg/kg时,不同母质发育的稻田土磷吸附能力降序排列为HS>HH>ZS>MS;当磷解吸量为0.188~14.320 mg/kg时,不同母质发育的稻田土磷解吸能力降序排列为ZS>MS>HS>HH;磷等温吸附曲线与Langmuir、Freundlich模型均能较好拟合,相关系数在0.945~0.995之间。总体而言,湖南省不同母质发育的稻田土对氮、磷的吸附解吸特征均不同,表现为黏性较强的紫色土固持氮的能力最强,可通过有效固持土壤溶液中的氮,降低氮流失风险;而沙性较强的麻砂泥对氮的固持能力最差,氮素流失风险较高;4种水稻土对磷的吸附能力均很强,且解吸率较低,说明湖南省主要稻田土壤对磷的吸附能力很强,流失风险相对较小。

Reddish clayey soil(HH),alluvial sandy soil(HS),granitic sandy soil(MS)and purple clayey soil(ZS)were used as the test materials to reveal the adsorption-desorption characteristics of nitrogen and phosphorus nutrients in paddy soils from different parent materials.The results showed that the nitrogen desorption amount of each soil was greater than the nitrogen adsorption amount in the low nitrogen concentration range of 0~10 mg/L;in the high nitrogen concentration range of 20~50 mg/L,the soil nitrogen desorption rate gradually decreased with the increase of nitrogen concentration of the equilibrium liquid;when the soil nitrogen adsorption amount was-57.267~352.400 mg/kg,the nitrogen adsorption capacity of the paddy soils from different parent materials was HS>ZS>HH>MS;when the nitrogen desorption amount was 8.367~37.833 mg/kg,the nitrogen desorption capacity of the paddy soils from different parent materials was HH>HS>MS>ZS;the nitrogen adsorption isothermal curves of HH,MS,HS and ZS fitted the Linear model,the correlation coefficients were 0.928~0.978.At the same time,in the range of low phosphorus concentration(0~10 mg/L),the phosphorus adsorption amounts of 4 paddy soils were greater than their phosphorus desorption amounts.When the phosphorus concentration of the equilibrium solution exceeded 10 mg/L,phosphorus fixation capacities of 4 paddy soils weakened,meanwhile their phosphorus desorption increased,but their adsorption amounts were still greater than their desorption amounts.When phosphorus adsorption and desorption amounts of 4 paddy soils were-110.312~534.961 and 0.188~14.320 mg/kg respectively,the phosphorus adsorption and desorption capacities of 4 paddy soils were HS>HH>ZS>MS and ZS>MS>HS>HH,respectively.The phosphorus adsorption isothermal curves of 4 paddy soils fitted the Langmuir and Freundlich models,the correlation coefficient were 0.945~0.995.In general,paddy soils developed from different parent materials in Hunan Province have different adsorption and desorption characteristics for nitrogen and phosphorus.Purple clayey soil has the strongest nitrogen fixation capacity due to its stronger viscosity,which can reduce the risk of nitrogen loss by effectively holding nitrogen in the soil solution.On the contrary,being of strong sandy property,granitic sandy soil has the worst nitrogen fixation capacity and higher risk of nitrogen loss.The four paddy soils have strong adsorption capacity and low desorption rate of phosphorus,which indicates that the main paddy soils in Hunan Province have strong adsorption capacity for phosphorus and relatively small loss risk.