摘要
摘要:为探究有机肥腐熟度对配施化肥氮利用率的作用机制，利用¹⁵N标记技术进行意大利生菜盆栽试验，从堆肥过程中选取不同腐熟度的有机肥[按照种子发芽指数（GI值）为50%、80%和100%进行堆肥的腐熟度区分]，研究施¹⁵NPK化肥（对照，CK）、¹⁵NPK+GI 50%有机肥（GI50）、¹⁵NPK+GI 80%有机肥（GI80）、¹⁵NPK+GI 100%有机肥（GI100）4个处理对意大利生菜化肥氮的转化、吸收和利用的影响。结果表明，与CK处理相比，添加有机肥处理意大利生菜生物量、¹⁵N吸收量与¹⁵N利用率分别显著提高30.5%~56.1%、40.0%~91.0%和15.5%~41.8%（P < 0.05），GI80处理较GI50处理生物量、¹⁵N吸收量与利用率分别显著提高17.1%、31.8%和35.4%（P < 0.05），GI100处理较GI50处理生物量、¹⁵N吸收量与利用率分别显著提高19.6%、15.8%和22.8%（P < 0.05）。试验期间，添加有机肥处理较CK处理土壤¹⁵NH₄⁺-N显著提高44.9%~74.2%（P < 0.05），¹⁵NO₃^--N显著降低8.4%~38.1%（P < 0.05），净硝化率显著降低10.8%~24.6%（P < 0.05）；GI80处理较GI50处理土壤¹⁵NH₄⁺-N提高7.9%~11.5%，¹⁵NO₃^--N显著降低18.5%~50.4%（P < 0.05），净硝化率显著降低15.0%~28.2%（P < 0.05）；GI100处理较GI50处理土壤¹⁵NH₄⁺-N显著提高11.5%~26.9%（P < 0.05），¹⁵NO₃^--N显著降低15.8%~22.7%（P < 0.05），净硝化率显著降低12.5%~23.9%（P < 0.05）。土壤微生物量氮（MB¹⁵N）缓慢上升，添加有机肥处理较CK处理显著提高67.3%~94.1%（P < 0.05），GI80处理较GI50处理提高6.0%~23.8%，GI100处理较GI50处理显著提高6.9%~25.5%（P < 0.05）。各处理MB¹⁵N占MBN的54.9%~71.6%（P < 0.05）。相关分析结果表明，MB¹⁵N、¹⁵NH₄⁺-N与¹⁵N吸收量、¹⁵N利用率呈现极显著正相关关系，且RDA分析结果说明MB¹⁵N是影响化肥¹⁵N吸收利用的关键驱动因子。因此，有机无机配施体系中适当增加有机肥的腐熟度（GI≥80%）能够明显增强土壤微生物的固氮能力，提高土壤氮素水平，减缓土壤铵态氮向硝态氮的转化速度，降低土壤净硝化速率，从而提高化肥氮的利用效率。
关键词:有机无机肥配施/
有机肥腐熟度/
化肥氮利用率/
土壤氮含量/
净硝化率/
¹⁵N标记技术
Abstract:The application of organic fertilizers promotes efficient chemical fertilizer use, but the effects and mechanisms of organic fertilizers with different maturation degrees are unresolved. To explore the effects of applying organic fertilizer with different maturity degrees on chemical nitrogen utilization efficiency for a practice of combined organic-inorganic fertilizers application, a pot experiment of lettuce (Lactuca sativa var. ramosa Hort.) was conducted using nitrogen-15 (¹⁵N) tracer technology. The organic fertilizers with different maturity degrees, which indicated by the germination index of cress (Lepidium sativum L.) (GI), were applied with ¹⁵N-labelled chemical fertilizer. A treatment without organic fertilizer application (CK) was set up as the control and following the principle of equal nutrient and carbon input, three treatments with different maturity degrees of organic fertilizer: ¹⁵NPK (nitrogen-15, phosphorus, potassium) + 50% GI organic fertilizer (GI50), ¹⁵NPK + 80% GI organic fertilizer (GI80), and ¹⁵NPK + 100% GI organic fertilizer (GI100) were tested. The results showed that, compared to CK, the GI50, GI80, and GI100 treatments significantly (P < 0.05) increased lettuce biomass, ¹⁵N uptake and ¹⁵N use efficiency by 30.5%-56.1%, 40.0%-91.0%, and 15.5%-41.8%, respectively. The biomass, ¹⁵N uptake, and ¹⁵N use efficiency of GI80 significantly (P < 0.05) increased by 17.1%, 31.8%, and 35.4%, respectively; those of GI100 significantly (P < 0.05) increased by 19.6%, 15.8%, and 22.8%, respectively, compared to GI50. Compared to CK, ammonium-nitrogen (¹⁵NH₄⁺-N) in GI50, GI80, and GI100 treatments significantly increased by 44.9%-74.2% (P < 0.05), nitrate-nitrogen(¹⁵NO₃^--N) significantly decreased by 8.4%-38.1% (P < 0.05), and net nitrification rate significantly decreased by 10.8%-24.6% (P < 0.05). Compared to GI50, GI80 increased ¹⁵NH₄⁺-N by 7.9%-11.5%, significantly decreased ¹⁵NO₃^--N and net nitrification rate by 18.5%-50.4% (P < 0.05) and 15.0%-28.2% (P < 0.05), respectively; GI100 significantly increased ¹⁵NH₄⁺-N by 11.5%-26.9% (P < 0.05), significantly decreased ¹⁵NO₃^--N and net nitrification rate by 15.8%-22.7% (P < 0.05) and 12.5%-23.9% (P < 0.05), respectively. The microbial biomass nitrogen (MBN) and MB¹⁵N in soil slowly increased. Compared to CK, GI80 and GI100 treatments significantly increased MB¹⁵N by 67.3%-94.1% (P < 0.05). Compared to GI50, GI80 and GI100 treatments increased MB¹⁵N by 6.0%-23.8% and 6.9%-25.5% (P < 0.05), respectively. The MB¹⁵N in each treatment accounted for 54.9%-71.6% (P < 0.05) of the MBN. Correlation analysis showed that MB¹⁵N and ¹⁵NH₄⁺-N had significant positive correlations with the ¹⁵N absorptive amount and ¹⁵N utilization rate; and the redundancy analysis showed that MB¹⁵N was the key driving factor of the absorption and utilization of ¹⁵N in chemical fertilizers. Therefore, an appropriate increase in the maturity of organic fertilizer (GI ≥ 80%) when applying organic and inorganic fertilizers can enhance the nitrogen fixation ability of soil microorganisms, improve soil nitrogen levels, slow the conversion rate of soil ¹⁵NH₄⁺-N to ¹⁵NO₃^--N, reduce the net nitrification rate, and inhibit soil nitrification, thereby improving the nitrogen utilization efficiency of chemical fertilizer. The results of this study provide an important basis for understanding the mechanisms of appropriately improving the maturity degree of organic matter to enhance chemical nitrogen use efficiency.
Key words:Combined application of organic and inorganic fertilizers/
Maturity degree of organic fertilizer/
Fertilizer nitrogen use efficiency/
Soil nitrogen content/
Net nitrification rate/
¹⁵N tracer technology



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