Critical review on soil phosphorus migration and transformation under freezing-thawing cycles and typical regulatory measurements

Freezing-thawing period plays an important role in the soil nutrient cycling. The frequency of freezing-thawing cycles (FTCs) can directly affect the supply of effective soil nutrients, further influences the growth and development of crops. Phosphorus is one of the essential nutrients for crop growth, and almost no compounds in gas form in nature, which is non-renewable resources. In modern agricultural production, phosphorus required by plants is mainly from the soil, but the utilization rate of phosphorus fertilizer in soil is generally only 10%–25%. Therefore, it is of great significance to study phosphorus migration and transformation behavior of soil in the non-growth period and related interfacial processes for improving the utilization efficiency of phosphorus fertilizer, increasing crop yield, reducing excessive application of phosphorus fertilizer, and subsiding environmental pollution. This paper systematically concludes key interfacial process of soil phosphorus in freezing-thawing soil system and relative mechanisms describing migration and transformation behavior of soil phosphorus. Besides, it summarizes the mediating effects of widely used soil conditioner on phosphorus cycling. The results show that freezing- thawing will destroy the structure of the soil, causing phosphorus to migrate along with runoff, soil water and heat movement. It also affects the types of microorganisms, the activity of microbial communities and the oxidation-reduction reaction of related minerals, making the phosphorus in soil from an unstable form to an active form. Biochar and humic substances can improve the physical and chemical properties of the soil, and have favorable effects on soil during freezing-thawing period. This review has important significance for the rational utilization of existing phosphorus resources, the maintenance of soil phosphorus cycle balance and the sustainable development of agriculture, meanwhile, has guiding significance for the reasonable utilization of agricultural wastes.