施用石灰对果园酸性土壤镁吸附-解吸特征的影响

Effect of lime application on characteristics of magnesium adsorption-desorption in acid soil of orchard

通过研究施用石灰对蜜柚果园酸性土壤镁吸附-解吸特性的影响,明确施用石灰对酸性土壤镁有效性的改良效果,为酸性土壤改良提供科学依据。以土壤培养试验以及田间石灰改良试验所采集土壤样品开展等温吸附试验,并以0.02 mol·L~(-1) Na NO_3进行解吸试验。结果表明,(1)随着石灰用量的增加,土壤p H及交换性盐基离子含量增加,且对果园不同土层土壤影响程度大小依次为0~10 cm(L1)>10~20 cm(L2)>20~40 cm(L3);(2)用Langmuir方程可以对吸附等温线进行较好拟合,描述土壤对镁的吸附作用(R~2=0.957~0.999),随着平衡液镁浓度的增加,土壤对镁的吸附量增加,吸附分配系数(K_d)下降。随着石灰施用量增加K_d上升,土壤固定镁的能力越强;(3)随着石灰用量的增加,土壤镁的解吸量先增加后下降,其大小依次为C2(1.8 mg·kg~(-1))>C3(3.6 mg·kg~(-1))>C1(0.9 mg·kg~(-1))>C0(0),而解吸率呈现逐步下降的趋势;(4)土壤镁的吸附能力与pH、有机质、交换性Ca~(2+)、交换性Mg~(2+)、盐基饱和度存在显著正相关性(P<0.05),与交换性酸、交换性Al~(3+)呈显著负相关(P<0.05),解吸能力则反之。综上所述,合理施用石灰可以有效地改善土壤酸度,增加土壤镁的吸附量和解吸量,提高土壤镁的有效性。

This study aims to determine the effect of lime application on the adsorption-desorption of magnesium characteristics in the acid soil of honey pomelo orchard,and to clarify the effect of liming on the soil magnesium availability,which will provide a scientific basis for the improvement of acidic soil.The research carried out the isotherm adsorption test with soil culture test and the soil samples collected in the field lime improvement test,and carried out desorption test with 0.02 mol·L-1 NaNO3.The results showed that,(1)with the increase of lime dosage,soil pH and exchangeable base cations concentration increased,and the influence degree in different soil layers was 0~10 cm(L1)>10~20 cm(L2)>20~40 cm(L3);(2)The Langmuir isotherm adsorption equation accurately described Mg sorption behavior in all soil samples(R2=0.957~0.999),with the increase of magnesium concentration in the equilibrium solution,the adsorption amount of soil magnesium increased and the adsorption distribution coefficient(Kd)decreased.With the increase of the amount of lime application,the Kd increased and the ability of soil to fix magnesium became stronger;(3)With the increase of lime application,the desorption amount of soil magnesium first increased and then decreased,the order of its size was C2(1.8 mg·kg-1)>C3(3.6 mg·kg-1)>C1(0.9 mg·kg-1)>C0(0),and the desorption rate showed a gradual decline;(4)The soil adsorption capacity of magnesium was positively correlated with pH,organic matter,exchangeable Ca2+,exchangeable Mg2+,and base saturation(P<0.05),and was significantly(P<0.05)negative with exchangeable acid and exchangeable Al3+,and the desorption capacity is opposite to adsorption capacity.In summary,rational lime application can effectively improve soil acidity,and the amount of adsorption and desorption of magnesium,and finally increase soil magnesium availability.