Recycling Manure as Vermicompost: Assessing Phosphorus Fertilizer Efficiency and Effects on Soil Health Under Different Soil Management

Abstract

Vermicompost from organic wastes can provide nutrients and benefits to soil health. Its effects on P availability to plants is still poorly understood, specially under different soil management practices. This work aimed to assess vermicompost as a P fertilizer able to enhance soil functioning. Phosphorus forms of vermicompost were studied by 31 P NMR and chemical P fractionation to explain its efficiency as fertilizer. This efficiency was assessed with a pot experiment using soil from two different soil management (conventional tillage–CT – and non-tillage–NT–) and from two depths (0–5 and 20–40 cm). Under NT, the soil showed a higher initial P bioavailability than under CT. In vermicompost, 65% of total P corresponded to ortophosphate, meanwhile 35.4% was extractable with neutral ammonium citrate. Overall, vermicompost increased the physiological P use efficiency by 87% compared to mineral fertilization, this increase being greater under CT (107%) than under NT (70%). Replacement values on a dry matter basis close or even higher than 100% were observed under CT and in subsurface soils under NT, conditions with the lowest P availability to plants. Vermicompost boosted microbial diversity in soils (by 8% according to Shannon index) and alkaline phosphatase and phytase activities, specially under NT. Vermicompost increased Fe and Zn uptake, while decreased the P to Zn molar ratio in spikes. Vermicompost can be a suitable replacement for P mineral fertilizer, in particular in soils with low P availability, providing further benefits such as improved Fe and Zn nutrition and increased microbial diversity and P cycling capacity in soils. Graphical Abstract

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