• ISSN 1008-505X
  • CN 11-3996/S

腐植酸基质缓释尿素对氮素淋失和氨挥发的阻控

Control of nitrogen leaching and ammonia volatilization by developing a kind of humic acid-matrix slow release urea

    摘要
  • 摘要:
    目的 基质缓释型氮肥(控失尿素)降低氮素释放的功能主要通过控失剂降低肥料中尿素的释放和在土壤中的转化而实现。腐植酸含有大量功能基团，施入土壤后可减少氮素的转化。本研究尝试了用腐植酸替代部分控失剂来改善基质缓释型氮肥对氮素的固持功能。
    方法 共采集了6种氮肥进行试验，包括普通尿素(urea，U)、控失剂添加比例分别为4%、6%、8%的3个基质缓释氮肥(LU1、LU2、LU3，LU—Loss-control urea)，以3.5%腐植酸等量替代LU2处理中的控失剂制备的腐植酸基质缓释氮肥(humic acid/loss-control urea，HLU)，以及添加了抗结剂(主要成分为纳米碳粉)的腐植酸基质缓释氮肥(humic acid/loss-control urea with anti-setting agent added，HLUA)。室内淋溶试验以不添加氮肥为对照，将6个肥料样品埋入土壤后，连续15天收集淋洗液，分析全氮、硝态氮和铵态氮含量，并采用氨气检测管法测定氨挥发速率。采用傅里叶变换红外光谱 (fourier transform infrared spectroscopy，FTIR)、核磁共振 (nuclear magnetic resonance，NMR) 和X射线光电子能谱分析 (X-ray photoelectron spectroscopy，XPS)、热重分析 (thermogravimetric analysis，TG)、比表面积吸附 (Brunauer-Emmett-Teller，BET)，分析了控失剂、尿素、基质缓释尿素和腐植酸基质缓释尿素的化学结构、孔隙结构以及热性质。
    结果 随着控失剂(control release agent，CLA)含量的增加，基质缓释尿素对氮素的固持作用增强，淋失和氨挥发量降低。与尿素 (U) 相比，LU1、LU2、LU3、HLU、HLUA的全氮累积淋溶量分别降低了24.5%、32.2%、34.9%、31.5%和32.2%，累积氨挥发量分别降低了13.1%、24.3%、27.1%、28.0%和29.5%。HLU、HLUA处理的氮素淋失和氨挥发量与LU2处理没有显著差异。化学结构表征分析表明，控失剂的主要成分凹凸棒土和腐植酸都与尿素形成了强度相当的分子间氢键，纳米碳粉与尿素间无氢键形成。在腐植酸基质缓释尿素中加入少量防结剂纳米碳粉，对其分子内氢键强度、热稳定性以及氮素淋失和氨挥发特征均没有显著影响。
    结论 在尿素中加入腐植酸、控失剂和防结剂制备的腐植酸基质缓释尿素，不仅加工和储存中不易粘连，具有较低的氮素淋失和氨挥发损失风险，还可作为一种兼具改良障碍土壤的多功能缓释肥料使用。

     

    Abstract:
    Objectives Matrix slow-release nitrogen fertilizer increases nitrogen use efficiency through preventing urea from quick release and hydrolysis in soil. Humic acid contains large amount of functional groups, and has been proved of preserving nutrient from leaching when applied into soil. So we replaced part of the loss control additives with humic acid for modification of nitrogen release and ammonia volatilization of loss control urea.
    Methods Six nitrogen fertilizers were chosen as test materials, including: common urea (U), three matrix slow-release urea products with high, medium and low ratio of loss control additives (LU1, LU2, and LU3), the matrix slow-release urea containing medium rate of loss control additives and equal rate of humic acid (HLU), and the HLU added with anti-setting agent (HLUA). All the fertilizers were buried in soil for leaching and ammonia volatilization monitoring experiment. The soils were leaching for 15 days, and the contents of total nitrogen, nitrate nitrogen and ammonium nitrogen in the leachate were analyzed. During the leaching period, ammonia tube method was used to monitor ammonia volatilization rate. Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance (NMR), X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TG), and specific surface area adsorption (BET) were used to characterize the chemical structure, pore structure and thermal properties of the loss control additives and the tested fertilizers.
    Results Compared with urea (U), the total soluble N in the leachates of LU1, LU2, LU3, HLU, and HLUA were decreased by 24.5%, 32.2%, 34.9%, 31.5%, and 32.2%, respectively, and the cumulative ammonia volatilization decreased by 13.1%, 24.3% and 27.1%, 28.0%, and 29.5%, respectively. Higher rate of loss control additives in matrix slow-release fertilizers showed declining nitrogen leaching and ammonia volatilization amount, and HLU and HLUA treatments were tested similar nitrogen leaching and ammonia volatilization amount with LU2. According to energy and structure analysis results, the loss control additives was composed of attapulgite and polymer, and the main component of the anti-coagulating agent was nano-carbon powder. Both attapulgite and humic acid formed intermolecular hydrogen bonds with urea, and the intramolecular hydrogen bonds of them were similar in strength and thermal stability. Nano-carbon did not form any bonds with the urea, and did not show any impact on the intramolecular hydrogen bond strength and thermal stability.
    Conclusions The humic acid-matrix slow release urea, which is prepared by adding humic acid, control loss additives and anti-coagulation agent into urea, is low in nitrogen leaching risk and ammonia volatilization loss, and its good stick-resistance characteristics made it suitable for procession and storage, so is a multifunctional slow-release fertilizer.

     

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