不同种类氮肥对紫色土表面电化学性质的影响

以紫色土为研究对象,采用土柱淋溶方法,研究了不同种类氮肥对紫色土表面电化学性质的影响。结果表明:氮肥处理的紫色土表面电荷量较原土大,增加量在0.05～0.7 cmol kg-1;在低氮水平(100、200 mg kg-1)下,紫色土表面电荷量为尿素硫铵硝铵;而在高氮水平(300、400 mg kg-1)下,表面电荷量为硫铵尿素硝铵。与原土相比,施肥处理的紫色土比表面积有所增加,其中施用100 mg kg-1尿素的增加量最大,较原土增加了78.04%,且尿素处理对土壤比表面积的影响显著高于其余两种氮肥处理;而400 mg kg-1硫铵处理的增加量最少,只增加了0.06%。在同一个施氮水平下,硫铵处理的土壤表面电荷密度和电场强度最大,而尿素处理的最小;低氮施肥处理对电荷密度和电场强度的影响明显高于高氮施肥处理。可见,不同氮肥种类和施氮水平由于电解质体系类型和浓度的差异,引起土壤pH变化,最终对土壤电化学性质产生影响,从而改变土壤养分的保蓄性和有效性。在本试验条件下,非电解质体系在低浓度下能显著影响紫色土表面电化学性质,而强电解质在高浓度下影响效果较为明显。

Effect of nitrogen fertilizer on surface electrochemical properties of purple soil relative to type of the fertilizer

Purple soil is an important type of soil resource, occupying an important position in agricultural production in China. The soil column leaching method was used in this experiment to explore effects of nitrogen fertilizer on purple soil surface electrochemical properties relative to type of the fertilizer and on nitrogen balance in the soil-crop system. Results show that compared with the original soil, purple soils in all fertilization treatments increased in surface charge by 0.05 ~ 0.7 cmol kg-1; the treatments low in nitrogen level (100 and 200 mg kg-1) displayed an order of Treatments U (Urea) > Treatments AS (ammonium sulfate) > Treatments AN (ammonium nitrate) in , surface charge; while the treatments high in nitrogen level (300 and 400 mg kg-1) did a different order of Treatments AS > Treatments U > Treatments AN; purple soils in all the treatments increased in specific surface area, particularly in Treatment N1 (100 mg kg-1 urea) being 78.04% higher than in CK; the effect of urea was much higher than the other two; Treatment L4 (400 mg kg-1 ammonium sulfate) was the lowest in the effect, being only 0.06% higher; among the treatments the same in N level, Treatment AS was the highest in both surface charge density and electric field strength, while Treatment U the lowest; the effect was apparently higher in treatments low in N level than in treatments high in N level. Obviously, N fertilizers, different in type and application rate, varied in type and concentration of electrolyte, thus leading to change in soil pH and eventually in soil electrochemical properties and hence in soil nutrient holding capacity and nutrient availability. In this experiment, the non-electrolyte system, when low in concentration, can significantly affect the surface electrochemical properties of purple soil, but the effect is obvious only when strong electrolyte is high in concentration.