黄土高原半干旱区覆膜和施磷对紫花苜蓿草地土壤磷组分的影响

Effects of film mulch and phosphorus application on soil phosphorus fractions in the semi-arid Loess Plateau alfalfa grassland

    摘要
  • 摘要: 在黄土高原半干旱区, 较低的土壤磷(P)有效性限制了紫花苜蓿(Medicago sativa L.)的生长。阐明连续覆膜和施磷对紫花苜蓿草地土壤磷组分的影响对合理施磷和提高紫花苜蓿草地生产力具有重要意义。试验设置2个覆膜处理(不覆膜和覆膜)和4个磷肥梯度0 kg(P)·hm−2、9.7 kg(P)·hm−2、19.2 kg(P)·hm−2和28.8 kg(P)·hm−2, 研究了覆膜和施磷在不同处理年限(3年和9年)对紫花苜蓿草地不同活性土壤磷组分及其影响因素的影响。结果表明, 与不覆膜相比, 覆膜处理第3年紫花苜蓿地上部分磷吸收量显著增加52.4%, 土壤Olsen-P、活性较高的NaHCO3-Po和NaHCO3-Pi以及中等活性的NaOH-Pi含量分别显著降低15.5%、20.2%、10.2%和27.9%; 覆膜处理第9年土壤NaHCO3-Po和NaHCO3-Pi含量显著增加37.3%和24.3%, 而地上部分磷吸收量、土壤Olsen-P和NaOH-Pi含量没有显著变化。与不覆膜相比, 无论处理年限长短, 覆膜均显著降低了活性较低的稀HCl-Pi含量, 显著提高了土壤NaOH-Po、浓HCl-Po和残留态磷(Residual-P)含量, 而对浓HCl-Pi和全磷含量没有显著影响。与不施磷相比, 除施磷处理第3年土壤残留态磷含量没有显著变化外, 施磷处理第3年和第9年紫花苜蓿地上部分磷吸收量、土壤全磷、Olsen-P以及所有磷组分含量均显著增加。冗余分析显示, 地上部分磷吸收量、土壤pH和碱性磷酸酶活性是影响土壤磷组分变化的主要因素。与不覆膜相比, 覆膜处理在第3年和第9年显著增加了土壤碱性磷酸酶活性, 在第9年显著降低土壤pH。与不施磷相比, 施磷处理在第3年和第9年显著降低了土壤pH, 在第9年显著降低了土壤碱性磷酸酶活性。综上, 覆膜可通过降低土壤pH和提高磷酸酶活性促进低活性磷组分向中、高活性磷组分转化, 所以将覆膜和施磷结合可有效提高紫花苜蓿草地土壤磷有效性和供磷潜力, 且随着处理年限的延长, 效果愈加明显。

     

    Abstract: Low available soil phosphorus (P) limits alfalfa (Medicago sativa L.) growth in the semi-arid Loess Plateau. Understanding the effects of continuous film mulch and P application on soil P fractions in alfalfa grasslands is crucial for optimizing P management and improving productivity. Two mulch treatments (no film mulch and film mulch) and four P fertilizer regimes 0, 9.7, 19.2, and 28.8 kg(P)∙hm−2 were employed to determine their effects on soil P fractions and their determinants in alfalfa grassland over different treatment durations (years 3 and 9). The results revealed that film mulching significantly increased P uptake by alfalfa shoots by 52.4%. Furthermore, mulching decreased soil Olsen P, high-activity NaHCO3-Po and NaHCO3-Pi, and medium-activity NaOH-Pi contents by 15.5%, 20.2% and 10.2%, and 27.9% in year 3, respectively. In year 9, film mulch markedly increased soil NaHCO3-Po and NaHCO3-Pi contents by 37.3% and 24.3%, respectively, but had no significant effect on alfalfa shoot P uptake and soil Olsen P and NaOH-Pi contents. Across both experimental years, film mulch reduced the content of diluted low-activity HCl-Pi, while significantly increasing soil NaOH-Po, concentrated HCl-Po, and residual-P contents. However, it had no significant effect on concentrated HCl-Pi and total P contents. Comparatively, P application significantly increased alfalfa shoot P uptake, soil total P, Olsen P, and all P fractions in years 3 and 9 compared with those of no P application, except for soil residual-P content in year 3. Redundancy analysis indicated that shoot P uptake, soil pH, and alkaline phosphatase activity were the main factors affecting changes in soil P fractions. Film mulch significantly increased soil alkaline phosphatase activity in both experimental years and decreased soil pH in year 9 compared with that of the mulch treatment. P application significantly decreased soil pH in years 3 and 9 and reduced soil alkaline phosphatase activity in year 9 compared with that of no P application. In conclusion, film mulch promotes the transformation of low-activity P fractions into medium- and high-activity P fractions by reducing soil pH and enhancing phosphatase activity. Therefore, the combination of film mulch and P application can improve the availability and supply potential of soil P in alfalfa grasslands, and these benefits increase over time.

     

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