Gypsum and phosphogypsum cut compost emissions better than lime
Ren X, Yang Q, Tang J, Sha Z
Soil Health
If you add lime to your garden beds or compost bin to sweeten the soil, this research shows that same lime boosts ammonia and carbon dioxide losses even as it curbs nitrous oxide, so the amendment you reach for changes what leaves your yard and enters the air.
Farmers and gardeners often add calcium-rich materials like lime, gypsum, or phosphogypsum to soil and compost to adjust pH and help plants grow. This huge review of 279 studies found that these materials don't just change the dirt, they also change how much nitrogen and carbon escape into the air as gases, some of which warm the planet and others of which smell like ammonia. The catch is that lime fights one gas while feeding another, so picking the right amendment depends on whether you're working with garden soil or a compost pile.
Key Findings
Liming cut nitrous oxide (N2O) emissions by 27.9% in soil and 36.5% in compost, but raised soil ammonia (NH3) by 68.4% and CO2 by 26%.
Phosphogypsum was the strongest ammonia reducer, cutting NH3 by 64.6% in soil and 54.8% in compost, and also lowered methane by 29.2% (soil) and 71.8% (compost).
Single superphosphate reduced compost N2O, CO2, and CH4 emissions by 25.2%, 14.1%, and 36.9% respectively, but increased soil CO2 by 5.4%, with effects depending on application rate, C/N ratio, and starting pH.
chevron_right Technical Summary
A massive analysis of 279 studies finds that common soil additives like lime and gypsum can cut harmful nitrogen and methane emissions from farms and compost piles, but the tradeoffs differ sharply depending on which amendment you use and whether it's applied to soil or a compost pile.
Abstract Preview
Original paper
Effects of calcium-based amendments on carbon and nitrogen emissions from soil and composting systems: a meta-analysis.
Nitrogen (N) and carbon (C) losses from cropping and livestock systems contribute significantly to global warming and other ecological crises. Calcium-based materials, such as lime, gypsum, phospho...
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Composting is the controlled decomposition of organic materials—such as plant waste, food scraps, and manure—into a nutrient-rich amendment that improves soil fertility and structure. For plant science, compost is significant because it enhances soil microbial communities, increases nutrient
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