Root-zone application of vermicompost to enhance phosphorus mineralization in saline soil

Abstract

Soil salinity poses a serious threat to global agricultural development, as it severely impacts the mineralization of nutrients, especially phosphorus, and hinders the normal growth of plants. Vermicompost significantly improved the chemical properties of saline-alkali soil, changed the soil microbial community and increased the nutrient uptake of plants. This study compared the effects of two vermicompost application methods, namely fully incorporated (40.27 g pot⁻¹) and concentrated in the root-zone application (6.04 g pot⁻¹), on phosphorus availability in saline soil. Vermicompost improved the bioavailability and uptake of phosphorus in the saline soil, especially with root-zone application. The root-zone treatment significantly increased the availability of phosphorus, including Resin-P (16.0 mg kg⁻¹ compared to 6.47 mg kg⁻¹ in the mixed treatment), NaHCO₃-Pi, and NaOH-P (6.21 mg kg⁻¹ vs 5.21 mg kg⁻¹), while reducing the content of Conc.HCl-P. Vermicompost concentrated in the root zone significantly reduced soil salinity around the roots, promoted the transformation of stable phosphorus into secondary active and active fractions, and significantly improved both phosphorus availability in saline soil and plant phosphorus use efficiency. Vermicompost application also increased the abundance of phosphorus-solubilizing bacteria, Saccharothrix, Lysinibacillus, Massilia and Ohtaekwangia with root-zone application than the control and fully-incorporated treatment. In addition, the root-zone treatment significantly improved maize shoot and root biomass, enhanced phosphorus and potassium uptake, and reduced the Na⁺ to Ca²⁺ ratio, thereby limiting salt translocation to roots. This study highlights the potential of root-zone application of vermicompost to improve saline-alkali soil, enhance crop growth, and elucidate phosphorus fractions transformation mechanisms driven by microbiota.

Graphical abstract

Keywords

mineralization / phosphorus fractions / soil salinity / vermicompost / root-zone

Highlight

	● Root-zone vermicompost treatment significantly affected soil phosphorus solubilizing bacteria and increased the biological availability of soil phosphorus.
	● The effect of root-zone vermicompost treatment to improve plant roots is better than that of fully incorporated to improve saline-alkali soil.
	● Root-zone vermicompost treatment could improve the phosphorus absorption status of maize root and promote its growth at seedling stage.

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