Enhancing Phosphorus Availability and Modifying Iron Distribution in Maize Using Nitrification Inhibitors

This study aimed to investigate the effects of nitrification inhibitors (NIs), specifically DMPP (Dimethyl pyrazole phosphate) and DMPFA (Dimethyl pyrazole fulvic acid), and plant growth-promoting microorganisms (PGPM) on nutrient uptake, allocation, and plant growth in maize under low phosphorus (P) availability. The research questions explored whether NIs enhance P, manganese (Mn), and zinc (Zn) uptake through rhizosphere acidification, alter nutrient partitioning between roots and shoots, and whether DMPFA-PGPM combinations synergistically improve plant growth and nutrient acquisition. Two rhizobox experiments were conducted using silt loam soil with low P content (8.7 mg kg⁻¹ P-CAL, pH 6.4). In the first experiment, maize was subjected to ten treatments, including ammonium (NH₄⁺) and nitrate (NO₃⁻) with or without DMPP, DMPFA, and rock phosphate (RP), compared to controls. The second experiment tested five treatments, including NH₄⁺ with DMPFA, fulvic acid, and Bacillus atrophaeus (ABi05) as PGPM. Measurements included rhizosphere pH, acid/alkaline phosphatase activity, root exudates, phytohormones, root morphology, plant biomass, and nutrient (P, Mn, Zn, Fe, Ca, Mg, K) concentrations in shoots and roots. Nutrient use efficiencies (PUE, PFPp, NRE) were calculated, and data were analyzed using one-way ANOVA with Fisher’s LSD test (p<0.05). In the first experiment, DMPP+RP and DMPFA+RP treatments increased biomass by 31.8% and 38.5%, respectively, compared to the negative control, with total root length rising by up to 169.5% in the positive control (NO₃⁻+soluble P). Shoot Fe content was 60% higher in NI treatments, with Mn and Zn shoot concentrations increasing by up to 40.4% and 32.8%, respectively, in DMPFA treatments. Rhizosphere pH dropped by 0.5 units in NI treatments, enhancing acid phosphatase activity. In the second experiment, DMPFA and DMPFA+ABi05 increased shoot biomass by 47.5% and 50.7%, respectively, and shoot P content by 45.1% and 62.7%. PUE was 56.2% higher with DMPFA+ABi05, and zeatin concentrations rose by 79.1% compared to controls. DMP-based NIs significantly enhance P, Mn, and Zn uptake in maize by acidifying the rhizosphere and increasing nutrient solubility. NIs shift mainly Fe and Mn allocation toward shoots, improving nutrient mobilization. The synergistic effect of DMPFA and PGPM (ABi05) further boosts PUE and Zeatin.

本研究旨在探究硝化抑制剂（Nitrification Inhibitors，NIs）——具体包括二甲基吡唑磷酸盐（Dimethyl pyrazole phosphate，DMPP）与二甲基吡唑黄腐酸（Dimethyl pyrazole fulvic acid，DMPFA）——以及植物生长促生微生物（Plant Growth-Promoting Microorganisms，PGPM）在低磷（Phosphorus，P）有效性条件下对玉米养分吸收、分配及植株生长的影响。本研究拟解答如下科学问题：硝化抑制剂能否通过根际酸化作用提升玉米对磷（P）、锰（Manganese，Mn）与锌（Zinc，Zn）的吸收效率，改变养分在根系与地上部的分配模式；以及DMPFA与PGPM的复合施用是否可协同促进植株生长与养分获取。本研究采用有效磷（P-CAL）含量为8.7 mg·kg⁻¹、pH值6.4的低磷粉砂壤土，开展两组根箱试验。第一组试验设置10个处理，包括施用铵态氮（NH₄⁺）、硝态氮（NO₃⁻）并分别添加或不添加DMPP、DMPFA与磷矿粉（Rock Phosphate，RP），并设置空白对照；第二组试验设置5个处理，包括施用铵态氮并添加DMPFA、黄腐酸以及作为PGPM的萎缩芽孢杆菌（Bacillus atrophaeus，ABi05）。本试验测定的指标包括根际pH、酸性/碱性磷酸酶活性、根系分泌物、植物激素、根系形态、植株生物量，以及地上部与根系的养分（P、Mn、Zn、Fe、Ca、Mg、K）浓度，同时计算了养分利用效率（PUE、PFPp、NRE），数据采用单因素方差分析（one-way ANOVA）结合Fisher氏最小显著差异检验（Fisher’s LSD test）进行统计分析，显著性水平设定为p<0.05。第一组试验结果显示，与空白对照相比，DMPP+RP与DMPFA+RP处理的植株生物量分别提升31.8%与38.5%；而阳性对照（NO₃⁻+可溶性磷）的总根长最高可增加169.5%。硝化抑制剂处理组的地上部铁（Fe）含量较对照提升60%，其中DMPFA处理组的地上部锰、锌浓度分别最高提升40.4%与32.8%；硝化抑制剂处理可使根际pH下降0.5个单位，进而增强酸性磷酸酶活性。第二组试验结果表明，DMPFA与DMPFA+ABi05处理的地上部生物量分别提升47.5%与50.7%，地上部磷含量分别提升45.1%与62.7%；DMPFA+ABi05处理的养分利用效率（PUE）较对照提升56.2%，玉米素（zeatin）浓度较对照升高79.1%。综上，基于DMP的硝化抑制剂可通过酸化根际环境、提升养分溶解度，显著促进玉米对P、Mn与Zn的吸收；硝化抑制剂主要将铁与锰向地上部分配，改善养分动员能力；而DMPFA与PGPM（ABi05）的协同作用可进一步提升养分利用效率与玉米素含量。