不同地表条件下生物炭对土壤氨挥发的影响

为了探究生物炭对不同地表条件下土壤氨挥发的作用及其效应,通过田间小区试验的方法,探讨生物炭与作物种植覆盖双重影响下,土壤氨的产生、土壤铵态氮含量、土壤脲酶活性的响应性变化.试验设置了6个处理,分别为CK+(未施生物炭+种植作物)、BC0.5+施用生物炭0.5 kg·(m~2·a)~(-1)+种植作物]、BC4.5+施用生物炭4.5 kg·(m~2·a)~(-1)+种植作物]、CK-(未施生物炭+裸地)、BC0.5-施用生物炭0.5 kg·(m~2·a)~(-1)+裸地]、BC4.5-施用生物炭4.5 kg·(m~2·a)~(-1)+裸地].结果表明在作物种植条件下,相对于CK+处理,BC4.5+、BC0.5+处理的土壤氨挥发随时间呈现先增加(前4 d内)后显著下降的态势,降幅分别为9.95%~61.80%、7.97%~50.52%(P0.05);但同期裸地条件下的BC4.5-、BC0.5-处理的土壤氨挥发较CK-处理则增加了40.02%~93.15%、28.09%~57.45%(P0.05).在等量生物炭施用条件下,作物种植土壤的氨挥发量明显低于裸地土壤,BC4.5+、BC0.5+较BC4.5-、BC0.5-处理分别降低了27.10%~92.10%、13.17%~83.45%(P0.05),但是CK+与CK-处理间的土壤氨挥发量差异不显著.上述结果说明作物种植覆盖地表对生物炭介导的土壤氨挥发具有一定的抑制效应.作物种植条件下,BC4.5+、BC0.5+处理较CK+处理的土壤铵态氮和脲酶含量的最大增幅依次为69.25%、72.73%和93.61%、90.56%(P0.05),但同期土壤氨挥发降低;而裸地条件下,BC4.5-、BC0.5-处理的土壤铵态氮和脲酶含量较CK-呈下降趋势明显,最大降幅依次为63.78%、95.70%和78.38%、92.64%(P0.05),同时土壤氨的挥发量上升.可见生物炭影响下的土壤氨挥发不仅与土壤铵态氮和脲酶含量的变化密切相关,且作物种植覆盖地表的影响更为深刻.

Effect of Biochar on Ammonia Volatilization from Soils of Different Surface Conditions

In order to explore the effect of biochar on the volatilization of ammonia in different surface soils, through the field test method, the responsiveness changes of ammonia volatilization, ammonium nitrogen, and urease were studied under the influence of biochar and crop cultivation. The study set six treatments:CK+, BC0.5+, and BC4.5+ (the biochar applied at 0, 0.5, 4.5 kg·(m²·a)^-1, respectively, under the condition of crop cultivation), and CK-, BC0.5-, and BC4.5- (the biochar applied at 0, 0.5, 4.5 kg·(m²·a)^-1, respectively, under the condition of bare land). The results showed that under the condition of crop cultivation, the ammonia volatilization of the BC4.5+ and BC0.5+ treatments increased in 4 days, then significantly decreased by 9.95%-61.80% and 7.97%-50.52% (P<0.05), respectively, with respect to CK+. However, compared with CK-, the ammonia volatilization of the BC4.5- and BC0.5- treatments increased by 40.02%-93.15% and 28.09%-57.45% (P<0.05), respectively. For the same amount of biochar application, the ammonia volatilization of the crop-planting soil was significantly lower than that of the bare land, and BC4.5+ and BC0.5+ declined by 27.10%-92.10% and 13.17%-83.45%(P<0.05), respectively, compared with the BC4.5- and BC0.5-, and there was no significant difference between CK+ and CK-. The above results indicated that biochar-mediated soil ammonia volatilization was inhibited by the surface cover. Moreover, with respect to CK+, the maximum increase rates of the contents of ammonium nitrogen and urease in the BC4.5+ and BC0.5+ treatments were orderly at 69.25% and 72.73% and 93.61% and 90.56% (P<0.05), but the soil ammonia volatilization decreased in the same period. The biggest decline of the soil NH₄⁺-N and urease content of BC4.5- and BC0.5- were 63.78% and 95.70% and 78.38% and 92.64% (P<0.05), respectively. Simultaneously, the soil ammonia volatilization rose in the bare land compared with CK-. Therefore, the soil ammonia volatilization was inversely related to soil NH₄⁺-N and urease under the influence of biochar, and the effect of crop planting was more profound.