秸秆-膨润土-聚丙烯酰胺对砂质土壤吸附氮素的影响

Effect of straw-bentonite-polyacrylamide composites on nitrogen adsorption of sandy soil

为提高土壤对氮素的吸附能力,减少土壤氮素流失,通过土壤培养试验和等温吸附试验研究了经堆腐的玉米秸秆、膨润土和聚丙烯酰胺(PAM)配制成的复合改良材料对砂质土壤NH4+-N吸附特性的影响。结果表明,复合改良材料对土壤NH4+-N吸附的影响随土培时间的延长呈先增大后减小的趋势,60d时最大。各处理NH4+-N的等温吸附曲线可用Langmuir方程很好地拟合。提高复合改良材料用量使砂质土壤NH4+-N的最大吸附量Qmax提高,吸附常数(k)降低,表明复合改良材料可以提高土壤对NH4+-N的吸附容量,但不能增加其吸附强度。同一用量下,Qmax随改良材料中PAM比例的提高呈先增大后减小的趋势,以PAM比例为0.99%时为最大,k则最低。提高复合改良材料用量使砂质土壤NH4+-N的最大缓冲容量(MBC)减小,改良材料中PAM添加比例对MBC无明显的影响规律。结果说明复合改良材料对土壤NH4+-N的保持量具有明显的促进作用,改良材料中PAM的添加比例以0.99%最佳。

In order to improve soil adsorption ability and decrease nitrogen loss,soil conditioners composited with cron straw,bentonite and polyacrylamide（PAM）were applied in sandy soil and incubated for 90 d.The effects of incubation time,proportion of PAM and rate of composite soil conditioners on soil nitrogen adsorption characteristics were investigated using isothermal adsorption experiments.The results showed that the quantity of NH4 ＋-N adsorpted by composite soil increased with incubation time but then decreased,which reached the maximum level at 60 d.The curves of isothermal adsorptions could be well fitted by Langmuir equation models.The maximum amount of NH4 ＋-N absorption（Qmax）increased with increasing composite proportion,but the absorption constant（k）decreased,which implied that the soil conditioners could improve the absorption capacity but reduce the strength of NH4 ＋-N adsorption by soils.Meanwhile,the adsorption amount of NH4 ＋-N increased then decreased as the proportion of PAM in the soil conditioner increased,with the highest Qmax value and the lowest k value being observed at the proportion of 0.99%for PAM.The maximum buffer capacity（MBC）for NH4 ＋-N of soils decreased significantly with the increasing rate of soil conditioners,but remained constant as the proportion of PAM changed.From the present study,it is concluded that straw-bentonite-PAM composite soil conditioner can improve the ability of nitrogen fixation,consequently decrease the loss of nitrogen from soils by increasing the NH4 ＋-N adsorption capacity of soils.The best proportion of PAM in the composite soil conditioner was 0.99%.