茶渣生物炭对茶园酸性土壤氮吸附——解吸特征及土壤酸性改良的影响

Effect of tea residue biochar on nitrogen adsorption-desorption characteristics and improvement of soil acidity of an acidic tea garden soil

为了探究添加茶渣生物炭对酸性茶园土壤氮吸附—解吸特性的影响,通过开展室内茶园土壤培养试验及等温吸附和解吸试验,分析不同热解温度(400℃、500℃、600℃)及不同添加配比(0.25%,0.5%,1.0%和2.0%)茶渣生物炭对酸性茶园土壤的理化性质及氮素吸附解吸特性的改良效果。结果表明,随着茶渣生物炭添加量增加,土壤pH、总有机碳、盐基饱和度、阳离子交换量、交换性钙和交换性镁含量显著增加;随着茶渣生物炭热解温度升高,土壤pH、总有机碳含量和盐基离子含量逐渐增加。茶渣生物炭对土壤铵态氮有明显的吸附作用,通过Langmuir方程可以对其吸附等温线进行较好的拟合(R2=0.968~0.987);随着吸附溶液中铵态氮浓度的增加,土壤对铵态氮的吸附量增加,吸附常数下降;土壤铵态氮的吸附分配系数(Kd)随着茶渣生物炭添加量增加逐渐升高,随着生物炭热解温度升高逐渐降低。土壤对铵态氮的解吸量在不同生物炭添加量处理中变化趋势为0.25%>1%>0.5%>2%;随着生物炭热解温度升高,土壤对铵态氮解吸量均升高;土壤对铵态氮吸附能力与土壤pH、总有机碳、交换性钾、交换性钙、盐基饱和度呈显著正相关(P<0.05),解吸能力则相反。研究表明,实际应用中应根据土壤改良的目的,优选茶渣生物炭添加配比及制备温度以达到最佳效果,对土壤保肥及提高土壤养分的利用率具有重要意义。

In order to study the effect of tea residue biochar on the nitrogen adsorption-desorption characteristics of acidic soil in tea gardens,tea residue biochar with different pyrolysis temperatures(400 ℃,500 ℃,600 ℃) and application ratios(0.25%,0.5%,1.0%,and 2.0%) were added into a tea garden soil.An incubation and an isothermal absorption and desorption experiment were carried out with the amended soils to study the improvement of biochar addition on soil physicochemical properties and nitrogen adsorption-desorption availability.Results showed that:soil pH,soil organic matter,base saturation(BS),cation exchange capacity,exchangeable Ca2+ and exchangeable Mg2+ contents significantly increased with the increase of biochar amendment,and soil pH,organic carbon,and salt-based ion gradually increased as the pyrolysis temperature of biochar increased.Tea residue biochar had obvious adsorption effect on soil NH4+-N with an adsorption isotherm well fitted by Langmuir equation(R2=0.968~0.987).The adsorption capacity of NH4+-N by the treated soils increased with the increase of NH4+-N concentration in the adsorption solution,while the equilibrium distribution coefficient decreased.The adsorption and distribution coefficient(Kd) of NH4+-N in treated soils gradually increased with the increase of biochar amendment,but it gradually decreased as the biochar pyrolysis temperature increased.The desorption of NH4+-N in treated soils decreased as follows:0.25%>1%>0.5%>2% biochar addition.As the biochar pyrolysis temperature increased,desorption of ammonia nitrogen elevated in all treatments.The adsorption capacity of soil for NH4+-N was significantly and positively correlated with soil pH,soil organic matter,exchangeable K+,exchangeable Ca2+,and BS(P<0.05).The desorption ability of soil for NH4+-N was opposite.In conclusion,in practical application,the addition ratio and preparation temperature of tea residue biochar should be optimized according to the purpose of soil improvement to achieve the best effect,which is of great significance for soil fertility conservation and improving the utilization rate of soil nutrients.