施用氮肥对石灰性土壤碳释放的影响

发布时间：2018-05-09 01:30

本文选题：石灰土壤 + 土壤CO_2释放　；参考：《西北农林科技大学》2017年硕士论文

【摘要】：由于温室气体排放的增加,二十世纪以来全球温度升高了0.6°C,由此带来的负面效应正严重威胁着人类的生存与发展。温室气体中CO_2在引发全球气候变动所占的比例最大,CO_2的权重约为60%。土壤碳库是全球陆地生态系统的主要碳库,土壤碳库包含有机和无机两大部分。近年来,我国农业生产中氮肥用量不断增加,由于铵态氮的硝化过程中释放H+,会降低土壤pH。施用氮肥对土壤碳释放的影响已有不少研究,北方石灰性土壤同时含有有机及无机碳,施用氮肥导致的土壤p H降低是否会影响石灰性土壤无机碳的释放,尚少见报道。硝化抑制剂可以抑制氮素的硝化过程,进而减缓土壤pH的降低幅度。因此,本文采用室内培养及田间田间试验方法探究了施用氮肥及与硝化抑制剂配合对石灰性土壤pH、硝铵态氮和土壤二氧化碳释放上碳释放的影响,旨在评价石灰性土壤碳释放的机理,为减少CO_2排放和稳定土壤碳库提供科学依据。获得以下主要结论:(1)以在西北农林科技大学进行了12年的长期定位常规模式下不施氮(N0)及施氮量120 kg ha-1(N120)和240 kg ha-1(N240)和3个处理为研究对象,连续两年(2015及2016)测定了不同施氮水平下石灰性土壤pH值、矿质态氮含量和CO_2释放量。连续两年的结果表明:两年的土壤pH变化趋势一致,都呈现先升高后降低的趋势,土壤pH在施用氮肥处理后显著降低。施肥处理两年的土壤铵态氮含量在两周内都降低到与不施氮无显著差异,说明硝化作用在两周内已完成。氮肥施用量越高,土壤CO_2释放量越高。试验结束时与N0处理相比,N120和N240处理的土壤CO_2累积释放量分别平均增加了30.6%和59.7%,显著高于N0处理。由于两年间的温度与降雨不同,2016年的土壤CO_2累积释放量稍低于2015年。(2)通过田间试验研究了不同施氮量及与硝化抑制剂(双氰胺,DCD)配合(N0、N160、N160+DCD、N220和N220+DCD)对土壤pH值、矿质态氮含量和二氧化碳(CO_2)释放量的影响。结果表明,施用氮肥显著降低了耕层土壤pH,与N0处理相比,N160和N220处理土壤pH平均降低了0.12个单位;配施DCD后,土壤pH降低幅度小于未加DCD处理。加入DCD使氮肥的硝化过程推迟了约20天时间。未加入DCD的处理土壤CO_2释放量随施氮量增加而增加,试验结束时(施肥37 d后)土壤CO_2累积释放量最高达到167.1 g m-2;与N0处理相比,N160和N220处理土壤CO_2累积释放量显著增加,增幅分别为20.9%和25.7%;N160+DCD和N220+DCD处理显著降低了土壤CO_2累积释放量,比对应相同施氮量处理分别降低了13.5%和11.0%。(3)采用密闭培养法研究了施用氮肥及其与硝化抑制剂(DCD)配合对不同利用方式(农田,果园,温室)石灰性土壤pH、铵态氮、硝态氮和CO_2释放量的影响。结果表明:与不施肥相比,仅施用氮肥显著降低了3种土壤的pH值,农田、果园和温室土壤pH在培养期间平均降低了0.44、0.39和0.15个单位;仅施用氮肥增加了培养期间土壤CO_2释放量,到培养结束时(48 d),农田、果园和温室土壤分别比相应不施氮土壤CO_2释放量平均增加了30.37%、24.49%和25.03%。氮肥配合加入DCD后,土壤铵态氮的硝化过程的进行显著被抑制,土壤p H的降低幅度明显低于仅施氮肥处理,农田、果园和温室土壤CO_2平均释放量较施氮肥分别降低了15%、8.9%和12.6%。
[Abstract]:Because of the increase of greenhouse gas emissions, the global temperature has risen by 0.6 C since twentieth Century, and the negative effects brought by the greenhouse gas are seriously threatening the survival and development of human beings. The proportion of CO_2 in the greenhouse gas is the largest in the global climate change, and the weight of CO_2 is about 60%. soil carbon pool is the main carbon pool of the global terrestrial ecosystem. The soil carbon pool contains two major organic and inorganic parts. In recent years, the amount of nitrogen fertilizer in agricultural production in China has been increasing. Due to the release of H+ in the nitrification process of ammonium nitrogen, there is a lot of research on the effect of nitrogen fertilizer on soil carbon release from soil pH. application. In the northern calcareous soil, there are organic and inorganic carbon, and the application of nitrogen fertilizer to soil P H Reducing the release of inorganic carbon in calcareous soils is rarely reported. Nitrification inhibitors can inhibit nitrification of nitrogen and slow down the reduction of soil pH. Therefore, the application of nitrogen fertilizer and nitrification inhibitor to pH, ammonium nitrate nitrogen, and nitrification inhibitors was investigated in the laboratory and field field experiments. The effect of carbon release from soil carbon dioxide release was aimed at evaluating the mechanism of carbon release from calcareous soil and providing scientific basis for reducing CO_2 emission and stabilizing soil carbon storage. The following main conclusions were obtained: (1) for 12 years in the Northwest Agriculture and Forestry University, nitrogen free (N0) and nitrogen application rate of 120 kg HA-1 (N120) and 2 were carried out at the Northwest Agriculture and Forestry University. 40 kg HA-1 (N240) and 3 treatments were used for two years (2015 and 2016) to determine the pH value, mineral nitrogen and CO_2 release at different levels of nitrogen application. The results of two two years showed that the trend of soil pH changes in two years was the same, and the soil pH was significantly reduced after the application of nitrogen fertilizer treatment. In two weeks, the soil ammonium nitrogen content decreased to no nitrogen application in two weeks, indicating that nitrification was completed within two weeks. The higher the amount of nitrogen fertilizer, the higher the release of soil CO_2. Compared with the N0 treatment, the cumulative release of CO_2 in soil treated by N120 and N240 increased by 30.6% and 59.7%, respectively. The cumulative release of soil CO_2 in 2016 was slightly lower than that in 2015. (2) the soil pH, mineral nitrogen and carbon dioxide (CO_2) release of different nitrogen application and nitrification inhibitors (N0, N160, N160+DCD, N220 and N220+DCD) were studied by field experiments in 2016. (2) the field experiment was conducted to study the amount of nitrogen and the amount of nitrogen application and nitrification inhibitors (DCD, N160, N160+DCD, N220 and N220+DCD). The results showed that the application of nitrogen fertilizer significantly reduced the soil pH in the plough layer. Compared with the N0 treatment, the pH of N160 and N220 treated soil pH decreased by 0.12 units. After the application of DCD, the decrease in soil pH was less than that of the non DCD treatment. The nitrification process of nitrogen fertilizer was delayed about 20 days by adding DCD. The cumulative release of soil CO_2 was up to 167.1 g m-2 at the end of the experiment (after 37 D fertilization). Compared with N0 treatment, the cumulative release of CO_2 in N160 and N220 treatments increased significantly, and the increase was 20.9% and 25.7%, respectively. N160+DCD and N220+DCD treatment significantly reduced the cumulative amount of soil cumulative release, compared with the same nitrogen application amount. The effects of nitrogen fertilizer application and nitrification inhibitor (DCD) on pH, ammonium nitrogen, nitrate nitrogen and CO_2 release of pH, ammonium nitrogen, nitrate nitrogen and CO_2 in different utilization methods (farmland, orchard, greenhouse) were studied by closed culture method. The results showed that the application of nitrogen fertilizer only decreased the pH value of 3 soils compared with no fertilizer. The soil pH in orchard and greenhouse soil decreased by 0.44,0.39 and 0.15 units during the incubation period. Nitrogen fertilizer application only increased the amount of CO_2 release in soil during culture, and at the end of culture (48 d), farmland, orchard and greenhouse soil increased by 30.37%, 24.49% and 25.03%. nitrogen fertilizer, respectively, after adding DCD to DCD. The nitrification process of soil ammonium nitrogen was significantly inhibited, and the decrease of P H in soil was significantly lower than that of nitrogen fertilizer only. The average release of CO_2 in farmland, orchard and greenhouse soil decreased by 15%, 8.9% and 12.6%., respectively.

【学位授予单位】：西北农林科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：S143.1

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