The bioavailability of soil amino acids and the regulation mechanism by environmental factors: A review

Soil contains great amount and all kinds of large and small molecular organic nitrogen, which are the main parts of soil nitrogen pool. Most plant species can absorb amino acids, peptides and even proteins directly, bypassing the decomposition by microorganism as suggested by traditional mineralization theory. Plants roots are able to absorb, transport and metabolize exogenous amino acids. Soil microorganisms are the main competitors for organic nitrogen with plant roots, and the active microorganism composition in different soils varies greatly. Environments play an important role in the absorption and metabolism of organic nitrogen by plants, however, the potential impact of global environmental changes on organic nitrogen nutrition has not been well studied. Accurate and quantitative analysis of the content and composition of soil organic nitrogen is needed for exploring the effect of the complex environmental changes on plant uptake of organic nitrogen, and determining the long-term contribution of soil organic nitrogen to plants nutrition.