The Claim
“Agriculture requires animal manure and cannot maintain soil fertility without livestock.”
We Need Animal Manure to Grow Crops
Quick Answer
The nitrogen cycle does not require animals. Biological nitrogen fixation by legumes is the original source of soil nitrogen. Plant-based alternatives (green manures, cover crops, composted plant materials) can provide equivalent fertility, and animal manure comes with significant environmental costs of its own. Note on evidence quality: One study cited on this page is a preliminary preprint from a small 0.19-hectare plot. Its findings are promising but should not be weighted equally with the peer-reviewed Muller et al. (2017, Nature Communications) modeling study or other large-scale analyses. Scalability of veganic farming to commercial agriculture remains an open and important question.
Supported by 2 cited sources
Evidence Summary
The Claim Modern agriculture depends on animal manure for nitrogen, phosphorus, and organic matter. Without livestock, we face a choice between environmentally destructive synthetic fertilizers or declining crop yields. ## What the Evidence Shows ### The Nitrogen Cycle Does Not Require Animals Biological nitrogen fixation by legumes is the original source of reactive nitrogen in terrestrial ecosystems.
Supporting Evidence
Nitrogen fixation via legume-microbe symbiosis predates animal agriculture and is the original terrestrial nitrogen source.
Based on controlled comparison in organic blackcurrant production (Ramos et al., 2021).
Sources & Evidence
2 sources cited across 2 claims
Legumes fix equivalent nitrogen to animal manure
Cohort StudyRed clover outperforms poultry manure for N and K
RCT