Abstract
Green manure effectively improves soil nutrients and crop yields, yet its partial substitution for chemical nitrogen fertilizer (CF) in maize systems remains underexplored in ecologically fragile Karst landscapes. To assess the effect of alfalfa green manure on maize yield, soil nutrients, enzymes, and microorganisms, we conducted a two-year field experiment comprising eight treatments: four CF levels (100%, 80%, 60%, and 0% of recommended CF) applied alone or combined with alfalfa green manure (CF100, AL_CF100, CF80, AL_CF80, CF60, AL_CF60, CF0, AL_CF0). The results showed that maize grain yield decreased with the sole reduction of chemical N fertilizer. Compared to the CF100 treatment, the AL_CF100 and AL_CF80 treatments significantly increased grain yield by an average of 21.8% and 16.9%, respectively. Additionally, the AL_CF60 treatment maintained maize grain yield in 2020 and significantly increased it in 2021. The AL_CF100 treatment significantly enhanced soil available N (AN) content, while soil Olsen-P (SOP) content and soil quality index (SQI) were significantly improved in the AL_CF100, AL_CF80, and AL_CF60 treatments. Alfalfa green manure application had no significant effect on soil bacterial and fungal communities. However, the CF rates positively influenced the relative abundances of bacterial phyla (Bacteroidota, Myxococcota, and Patescibacteria) and genera (Intrasporangium, Streptomyces, and Quadrisphaera), as well as fungal genera (Exophiala and Setophoma). α-Diversity analysis revealed that partial substitution of CF with alfalfa green manure did not significantly affect soil bacterial diversity (Ace, Shannon, and Sobs indices) or richness (Chao value). In contrast, chemical N fertilizer rates significantly altered the β-diversity of both bacteria and fungi. The soil AN, AK, sucrase activity, and the relative abundances of Bacteroidota, Streptomyces, and Instrasporangium showed significant positive relationship with maize grain yield. This study demonstrates that substituting 20% CF with alfalfa green manure optimizes maize productivity while enhancing soil health in Karst agroecosystems.
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Claims 19
Claim · model-written summary
Sole reduction of chemical N fertilizer decreased maize grain yield.
Zea maysNot reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“maize grain yield decreased with the sole reduction of chemical N fertilizer”
Claim · model-written summary
AL_CF100 significantly increased maize grain yield by 21.8% compared with CF100.
- Treatment
- AL_CF100e1
- Outcome
- grain yielde1
- Direction
- increasede1
- Value
- 21.8%e1
- Comparator
- CF100e1
- Setting
- two-year field experimente2
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“maize grain yield decreased with the sole reduction of chemical N fertilizer”
e1“Compared to the CF100 treatment, the AL_CF100 and AL_CF80 treatments significantly increased grain yield by an average of 21.8% and 16.9%, respectively”
e2“we conducted a two-year field experiment”
Claim · model-written summary
AL_CF80 significantly increased maize grain yield by 16.9% compared with CF100.
- Treatment
- AL_CF80e1
- Outcome
- grain yielde1
- Direction
- increasede1
- Value
- 16.9%e1
- Comparator
- CF100e1
- Setting
- two-year field experimente2
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“maize grain yield decreased with the sole reduction of chemical N fertilizer”
e1“Compared to the CF100 treatment, the AL_CF100 and AL_CF80 treatments significantly increased grain yield by an average of 21.8% and 16.9%, respectively”
e2“we conducted a two-year field experiment”
Claim · model-written summary
AL_CF60 maintained maize grain yield in 2020.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“maize grain yield decreased with the sole reduction of chemical N fertilizer”
e1“the AL_CF60 treatment maintained maize grain yield in 2020 and significantly increased it in 2021”
Claim · model-written summary
AL_CF60 significantly increased maize grain yield in 2021.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“maize grain yield decreased with the sole reduction of chemical N fertilizer”
e1“the AL_CF60 treatment maintained maize grain yield in 2020 and significantly increased it in 2021”
Claim · model-written summary
AL_CF100 significantly enhanced soil available N content.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“maize grain yield decreased with the sole reduction of chemical N fertilizer”
e1“The AL_CF100 treatment significantly enhanced soil available N (AN) content”
Claim · model-written summary
AL_CF100 significantly improved soil Olsen-P content and soil quality index.
- Treatment
- AL_CF100e1
- Outcome
- soil Olsen-P (SOP) content and soil quality index (SQI)e1
- Direction
- improvede1
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“maize grain yield decreased with the sole reduction of chemical N fertilizer”
e1“soil Olsen-P (SOP) content and soil quality index (SQI) were significantly improved in the AL_CF100, AL_CF80, and AL_CF60 treatments”
Claim · model-written summary
AL_CF80 significantly improved soil Olsen-P content and soil quality index.
- Treatment
- AL_CF80e1
- Outcome
- soil Olsen-P (SOP) content and soil quality index (SQI)e1
- Direction
- improvede1
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“maize grain yield decreased with the sole reduction of chemical N fertilizer”
e1“soil Olsen-P (SOP) content and soil quality index (SQI) were significantly improved in the AL_CF100, AL_CF80, and AL_CF60 treatments”
Claim · model-written summary
AL_CF60 significantly improved soil Olsen-P content and soil quality index.
- Treatment
- AL_CF60e1
- Outcome
- soil Olsen-P (SOP) content and soil quality index (SQI)e1
- Direction
- improvede1
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“maize grain yield decreased with the sole reduction of chemical N fertilizer”
e1“soil Olsen-P (SOP) content and soil quality index (SQI) were significantly improved in the AL_CF100, AL_CF80, and AL_CF60 treatments”
Claim · model-written summary
Alfalfa green manure had no significant effect on soil bacterial and fungal communities.
Not reportedComparatorDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“maize grain yield decreased with the sole reduction of chemical N fertilizer”
e1“Alfalfa green manure application had no significant effect on soil bacterial and fungal communities”
Claim · model-written summary
CF rates positively influenced the relative abundances of bacterial phyla Bacteroidota, Myxococcota and Patescibacteria.
- Treatment
- CF ratese1
- Outcome
- relative abundances of bacterial phylae1
- Direction
- positively influencede1
- Qualifier
- Bacteroidota, Myxococcota, and Patescibacteriae1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“maize grain yield decreased with the sole reduction of chemical N fertilizer”
e1“the CF rates positively influenced the relative abundances of bacterial phyla (Bacteroidota, Myxococcota, and Patescibacteria) and genera (Intrasporangium, Streptomyces, and Quadrisphaera), as well as fungal genera (Exophiala and Setophoma)”
Claim · model-written summary
CF rates positively influenced the relative abundances of bacterial genera Intrasporangium, Streptomyces and Quadrisphaera.
- Treatment
- CF ratese1
- Outcome
- relative abundancese1
- Direction
- positively influencede1
- Qualifier
- genera (Intrasporangium, Streptomyces, and Quadrisphaera)e1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“maize grain yield decreased with the sole reduction of chemical N fertilizer”
e1“the CF rates positively influenced the relative abundances of bacterial phyla (Bacteroidota, Myxococcota, and Patescibacteria) and genera (Intrasporangium, Streptomyces, and Quadrisphaera), as well as fungal genera (Exophiala and Setophoma)”
Claim · model-written summary
CF rates positively influenced the relative abundances of fungal genera Exophiala and Setophoma.
- Treatment
- CF ratese1
- Outcome
- relative abundancese1
- Direction
- positively influencede1
- Qualifier
- fungal genera (Exophiala and Setophoma)e1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“maize grain yield decreased with the sole reduction of chemical N fertilizer”
e1“the CF rates positively influenced the relative abundances of bacterial phyla (Bacteroidota, Myxococcota, and Patescibacteria) and genera (Intrasporangium, Streptomyces, and Quadrisphaera), as well as fungal genera (Exophiala and Setophoma)”
Claim · model-written summary
Partial substitution of CF with alfalfa green manure did not significantly affect soil bacterial diversity.
- Treatment
- partial substitution of CF with alfalfa green manuree1
- Outcome
- soil bacterial diversity (Ace, Shannon, and Sobs indices)e1
Not reportedComparatorDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“maize grain yield decreased with the sole reduction of chemical N fertilizer”
e1“partial substitution of CF with alfalfa green manure did not significantly affect soil bacterial diversity (Ace, Shannon, and Sobs indices) or richness (Chao value)”
Claim · model-written summary
Partial substitution of CF with alfalfa green manure did not significantly affect soil bacterial richness (Chao value).
Not reportedComparatorDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“maize grain yield decreased with the sole reduction of chemical N fertilizer”
e1“partial substitution of CF with alfalfa green manure did not significantly affect soil bacterial diversity (Ace, Shannon, and Sobs indices) or richness (Chao value)”
Claim · model-written summary
Chemical N fertilizer rates significantly altered the beta-diversity of both bacteria and fungi.
- Treatment
- chemical N fertilizer ratese1
- Outcome
- β-diversity of both bacteria and fungie1
- Direction
- alterede1
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“maize grain yield decreased with the sole reduction of chemical N fertilizer”
e1“chemical N fertilizer rates significantly altered the β-diversity of both bacteria and fungi”
Claim · model-written summary
Soil AN, AK and sucrase activity showed a significant positive relationship with maize grain yield.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“maize grain yield decreased with the sole reduction of chemical N fertilizer”
e1“The soil AN, AK, sucrase activity, and the relative abundances of Bacteroidota, Streptomyces, and Instrasporangium showed significant positive relationship with maize grain yield”
Claim · model-written summary
Relative abundances of Bacteroidota, Streptomyces and Instrasporangium showed a significant positive relationship with maize grain yield.
- Interactor
- Bacteroidota, Streptomyces, and Instrasporangiume1symbiont
- Outcome
- maize grain yielde1
- Direction
- positivee1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“maize grain yield decreased with the sole reduction of chemical N fertilizer”
e1“The soil AN, AK, sucrase activity, and the relative abundances of Bacteroidota, Streptomyces, and Instrasporangium showed significant positive relationship with maize grain yield”
Claim · model-written summary
Substituting 20% CF with alfalfa green manure optimizes maize productivity while enhancing soil health (author conclusion).
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“maize grain yield decreased with the sole reduction of chemical N fertilizer”
e1“substituting 20% CF with alfalfa green manure optimizes maize productivity while enhancing soil health”
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