Straw beats manure at unlocking buried soil phosphorus for crops
Wang Y, Fan H, Yang X, Wang Z, Shang J
Soil Health
If you compost or mulch with straw instead of manure, you're not just feeding this year's plants, you're coaxing soil microbes to release phosphorus that's been locked away from years of past fertilizing.
Greenhouse vegetable soils often have huge amounts of phosphorus buried from years of heavy fertilizing, but plants can't easily reach it. Researchers found that adding straw, or straw treated with a wood-derived compound called lignin, got pakchoi plants to grow bigger and pull in much more phosphorus than chicken manure did, essentially by shifting the carbon-to-phosphorus balance and encouraging helpful soil microbes rather than dumping in more phosphorus. Straw alone gave the biggest growth boost, while the lignin-treated version also fixed soil acidity, making it a gentler, lower-pollution way to feed crops using nutrients already sitting in the ground.
Key Findings
Straw and lignin-modified straw amendments increased pakchoi shoot dry weight by 47.0% and 12.4% respectively, and boosted shoot phosphorus uptake by 80.2% and 76.8%, compared to chicken manure.
Chicken manure caused a phosphorus surplus (adding more than plants removed), while straw-based amendments created negative phosphorus balances, meaning they drew down legacy phosphorus already in the soil rather than adding new accumulation.
High-carbon, low-phosphorus plant amendments raised soil carbon-to-phosphorus ratio and pH, boosted microbial enzyme activity for carbon and nitrogen cycling, and reduced signs of microbial phosphorus limitation, with gains tied to overall nutrient balance and microbial community shifts rather than one specific phosphorus-cycling pathway.
chevron_right Technical Summary
Adding straw or lignin-treated straw to overfertilized greenhouse soil helped pakchoi plants grow bigger and absorb far more phosphorus than chicken manure did, all while tapping into phosphorus already stockpiled in the soil instead of adding more. That's a promising way to cut phosphorus pollution from decades of over-fertilizing without starving the crop.
Abstract Preview
Original paper
Plant-derived high-C:P amendments enhance legacy phosphorus utilization in phosphorus-enriched greenhouse soil via stoichiometric regulation and microbial functional coupling.
Long-term intensive fertilization has accumulated large legacy phosphorus (P) pools in greenhouse vegetable soils, while substituting chemical fertilizers with livestock manure may exacerbate soil ...
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