有机氮肥对马来西亚沙捞越州酸性土壤玉米干物质产量及铵态氮和硝态氮含量的影响

腐殖质中的腐植酸和黄腐酸可以提高土壤中可交换性铵（NH4＋）的回收率。这两种酸固定和保持NH4＋的能力已经在许多研究中得到了证实，二者通过提高植株的光合作用速率、促进根系发育影响植物的生长和养分吸收。因此，本研究调查了这两种酸（液态）对玉米干物质产量、土壤铵态氮和硝态氮（NO3-）含量的影响。根据液态有机氮肥的组成，采用标准方法分离提纯腐植酸。有机氮肥在玉米种植后第10天、第28天分别施入盆栽土壤，然后在种植后第54天或孕穗期采集植株和土壤样品。土壤样品分析PH、铵态氮和硝态氮含量，植株样品测定干物质产量。结果表明，在酸性条件下，液态有机氮肥（黄腐酸、腐植酸或二者同时施用）的施用可以提高土壤中NH4＋的累积量。随土壤活性碳储量的增加，腐植酸分子上羧基官能团对土壤NH4＋的吸附能力增强。然而，酸含量较低时对干物质产量的影响明显减小。各处理间硝态氮的有效性没有达到统计上的差异显著水平。较低的PH值能抑制土壤硝化作用进程，同时降低土壤NO3-含量。这表明液态腐植酸和／或黄腐酸在提高尿素利用效率方面发挥着重要作用。然而，与腐植酸分子特性有关的作用机理还需要进一步详细研究。本研究为液态和叶面有机肥料的发展提供一定的依据。

Effect of Organic Based N Fertilizer on Dry Matter(Zea mays L.),Ammonium and Nitrate Recovery in an Acid Soil of Sarawak,Malaysia

Problem statement:Exchangeable ammonium(NH4+)could be recovered by humic and fulvic acids from humic substances.The ability of these acids in fixing or retaining NH4+ has been demonstrated in many findings and reports.Both acids could affect the plant growth,nutrients uptake by enhancing photosynthesis rate and root growth among others.Thus,in this study,the effect of both acids(in liquid form)on soil exchangeable NH4+,dry matter production and available nitrate(NO3ˉ) was investigated.Approach:Humic molecules were isolated using standard procedures,followed by liquid organic N fertilizers formulation.Organic based N fertilizers were applied to soil in pots at 10 days After Planting(DAP)and 28 DAP.Treated soils and plant parts were sampled at 54 DAP or at tasselling stage.Soil samples were analyzed for pH,ammonium and nitrate content.The plant samples were weighed to assess dry matter production.Results:Under acid condition,organic based liquid N fertilizers(fulvic acid or both,humic and fulvic acids)increased accumulation of NH4+in soil.The presence of carboxylic groups in humic molecules increased NH4+ retention with increasing soil’s stock labile carbon.However,low percentage of these acids reduced their full effect on dry matter production.The availability of nitrate was not statistically different for all treatments.Low soil pH could had reduced nitrification processes and simultaneously soil NO3ˉcontent.Conclusion:Liquid form of humic and/or fulvic acids could play an important role in enhancing urea efficiency.However,their contribution needs to be studied in detail in relation to humic molecules characteristics.This study had a potential in the development of liquid and foliar organic fertilizers.