Effects of different planting ratios of broomcorn millet （Panicum miliaceum） on ammonia-oxidizing and denitrifying microorganisms in rhizosphere soil of alfalfa （Medicago sativa）

doi:10.11686/cyxb2024369

Abstract

Abstract:

Companion planting of broomcorn millet （Panicum miliaceum） with alfalfa （Medicago sativa） can improve nitrogen utilization. To explore the mechanism of this effect， we investigated the impact of different planting ratios of broomcorn millet and alfalfa on ammonia-oxidizing archaea （AOA）， ammonia-oxidizing bacteria （AOB）， denitrifying microorganisms （nirK-， nirS-， and nosZ-containing microbes）， and other soil factors in alfalfa rhizosphere soil under companion planting in the dry farming area of the Loess Plateau. Four broomcorn millet-alfalfa planting ratios ［1∶1 （1P1M）， 1∶2 （1P2M）， 1∶3 （1P3M）， and 2∶3 （2P3M）］ were established with alfalfa monoculture （M） as the control. The diversity， structure， composition， and co-occurrence network of ammonia-oxidizing and denitrifying microorganisms in alfalfa rhizosphere soil were determined by high-throughput sequencing， and their correlations with soil factors were analyzed. The results showed that， as the ratio of broomcorn millet increased， the soil total nitrogen content and stable carbon and nitrogen isotope values increased， and significantly increased in 2P3M （P<0.05）； and the soil organic carbon content first decreased and then increased， with a significant decrease in 2P3M （P<0.05）. Companion planting increased the richness of ammonia-oxidizing and nosZ-containing microorganisms， but decreased the richness of nirK-containing microorganisms. The alpha diversity of AOA was sensitive to the planting ratio. However， a beta diversity analysis revealed no significant differences in ammonia-oxidizing and denitrifying community structures among the different planting ratios. Nitrososphaera and Nitrosospira were the dominant genera of AOA and AOB， respectively， accounting for over 85% of their communities based on abundance. The denitrifying microbial community was enriched in genera that promote plant growth and nutrient transformation， such as Achromobacter among the nirK-containing microorganisms and Azoarcus among the nirS-containingmicroorganisms. A co-occurrence network analysis revealed a more complex co-occurrence network of soil ammonia-oxidizing and denitrifying communities in 2P3M than in the other treatments， and this was mainly evident in the network complexity and modularity indicators. The contents of total nitrogen and calcium and magnesium ions were significantly correlated with AOA microbial diversity， and the contents of soil organic carbon and cadmium ions were significantly correlated with AOB and nirS microorganisms. In summary， companion planting affected the diversity， composition， and co-occurrence network of ammonia-oxidizing and denitrifying microorganisms in the rhizosphere soil of alfalfa， revealing the microbial mechanism of efficient nitrogen utilization under this technology. Based on these results， the broomcorn millet∶alfalfa planting ratio of 2∶3 appears to be the most effective for exploiting the advantages of companion planting.

Key words: companion planting, ammonia oxidation, denitrification, functional gene, diversity, co-occurrence network

Ruo-xuan LI, Sheng-zhi-can LI, Yi-tong CHEN, Yu-hao SUN, Pei-zhi YANG, Yan-nong CUI, Ming-xiu LONG, Shu-bin HE. Effects of different planting ratios of broomcorn millet （Panicum miliaceum） on ammonia-oxidizing and denitrifying microorganisms in rhizosphere soil of alfalfa （Medicago sativa）[J]. Acta Prataculturae Sinica, 2025, 34(6): 110-121.

Figures/Tables 7

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功能基因 Functional genes	引物Primers	引物序列Primer sequences （5′—3′）	长度Length （bp）	参考文献Reference
AOA	Arch-amoA26F Arch-amoA417R	GACTACATMTTCTAYACWGAYTGGGC GGKGTCATRTATGGWGGYAAYGTTGG	417	［18］
AOB	amoA1F amoA2R	GGGGTTTCTACTGGTGGT CCCCTCKGSAAAGCCTTCTTC	500	［19］
nirK	NIRK-F NIRK-R	TCATGGTGCTGCCGCGYGANGG GAACTTGCCGGTKGCCCAGAC	400	［20］
nirS	CD3AF R3CDR	GTSAACGTSAAGGARACSGG GASTTCGGRTGSGTCTTGA	400	［21］
nosZ	NOSZ-1126F NOSZ-1381R	GGGCTBGGGCCRTTGCA GAAGCGRTCCTTSGARAACTTG	400	［22］

功能基因 Functional genes	引物Primers	引物序列Primer sequences （5′—3′）	长度Length （bp）	参考文献Reference
AOA	Arch-amoA26F Arch-amoA417R	GACTACATMTTCTAYACWGAYTGGGC GGKGTCATRTATGGWGGYAAYGTTGG	417	［18］
AOB	amoA1F amoA2R	GGGGTTTCTACTGGTGGT CCCCTCKGSAAAGCCTTCTTC	500	［19］
nirK	NIRK-F NIRK-R	TCATGGTGCTGCCGCGYGANGG GAACTTGCCGGTKGCCCAGAC	400	［20］
nirS	CD3AF R3CDR	GTSAACGTSAAGGARACSGG GASTTCGGRTGSGTCTTGA	400	［21］
nosZ	NOSZ-1126F NOSZ-1381R	GGGCTBGGGCCRTTGCA GAAGCGRTCCTTSGARAACTTG	400	［22］

处理 Treatments	土壤有机碳 SOC （g·kg^-1）	总氮 TN （g·kg^-1）	铵态氮 NH₄⁺-N （mg·kg^-1）	硝态氮 NO₃^--N （mg·kg^-1）	稳定碳同位素 δ¹³C（‰）	稳定氮同位素 δ¹⁵N（‰）	钙离子 Ca²⁺ （mg·kg^-1）	镁离子 Mg²⁺ （mg·kg^-1）	镉离子 Cd²⁺ （mg·kg^-1）
M	5.49±0.55a	0.27±0.07bc	4.98±0.92a	2.96±0.50a	-7.20±0.08b	26.35±2.12b	4.59±0.27c	35.83±0.01ab	0.040±0.00a
1P3M	4.18±0.87b	0.22±0.02c	4.22±0.49a	3.02±0.70a	-7.03±0.38ab	26.71±4.51ab	5.42±0.26a	39.92±2.43a	0.039±0.00ab
1P2M	4.44±0.97ab	0.25±0.05bc	4.63±1.04a	2.89±0.44a	-6.81±0.44ab	26.81±1.77ab	5.20±0.43ab	38.93±3.02ab	0.033±0.01b
2P3M	4.23±0.57b	0.41±0.04a	4.67±1.03a	2.99±0.98a	-6.62±0.22a	32.12±3.89a	4.73±0.47bc	36.27±3.43ab	0.039±0.00ab
1P1M	5.16±0.66ab	0.31±0.08b	4.52±0.83a	3.01±0.38a	-6.99±0.34ab	27.33±2.25ab	4.39±0.07c	34.84±2.57b	0.036±0.01ab

处理 Treatments	土壤有机碳 SOC （g·kg^-1）	总氮 TN （g·kg^-1）	铵态氮 NH₄⁺-N （mg·kg^-1）	硝态氮 NO₃^--N （mg·kg^-1）	稳定碳同位素 δ¹³C（‰）	稳定氮同位素 δ¹⁵N（‰）	钙离子 Ca²⁺ （mg·kg^-1）	镁离子 Mg²⁺ （mg·kg^-1）	镉离子 Cd²⁺ （mg·kg^-1）
M	5.49±0.55a	0.27±0.07bc	4.98±0.92a	2.96±0.50a	-7.20±0.08b	26.35±2.12b	4.59±0.27c	35.83±0.01ab	0.040±0.00a
1P3M	4.18±0.87b	0.22±0.02c	4.22±0.49a	3.02±0.70a	-7.03±0.38ab	26.71±4.51ab	5.42±0.26a	39.92±2.43a	0.039±0.00ab
1P2M	4.44±0.97ab	0.25±0.05bc	4.63±1.04a	2.89±0.44a	-6.81±0.44ab	26.81±1.77ab	5.20±0.43ab	38.93±3.02ab	0.033±0.01b
2P3M	4.23±0.57b	0.41±0.04a	4.67±1.03a	2.99±0.98a	-6.62±0.22a	32.12±3.89a	4.73±0.47bc	36.27±3.43ab	0.039±0.00ab
1P1M	5.16±0.66ab	0.31±0.08b	4.52±0.83a	3.01±0.38a	-6.99±0.34ab	27.33±2.25ab	4.39±0.07c	34.84±2.57b	0.036±0.01ab

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