Effect of Drying Duration and Temperature on the Amount of Water‐Extractable Organic and Inorganic Phosphorus in Soil Samples

ABSTRACT Determination of the precise quantity of plant‐available phosphorus (P) is imperative to ensure a sufficient supply of nutrients to plants. As a basis for this, the preparation of soil samples has been shown to exert a substantial influence on the extractability of nutrients. To clarify the effects of drying time and temperature of soil samples, water extracts are used with subsequent determination of organic and inorganic P, leading to the finding that an increase in water‐extractable P during the drying process cannot be solely attributed to the decrease in soil water content. Furthermore, we observed that higher temperatures result in an increase of water extractable P, up to a temperature between 40°C and 105°C. However, it is crucial to note that the temperature effects on water‐extractable P differ between organic and inorganic P forms. High temperatures during transport, storage, or sample preparation should be avoided to ensure comprehensive interpretation of results and precise fertilizer recommendations.