Urea and pH of the soil

[DarioU]

Hello everyone, it is not clear to me how urea modifies the pH of the soil. Does it increase or decrease the pH? We know that at least in part it is absorbed degraded into ammonium ions and therefore should make the soil more acidic but in part it is also absorbed directly as urea. Anyone know how it works? I can't find anything for sure in my books. Thank you all.

 

[cnycharles]

In a few hours, urea will raise pH slightly then usually in short and long term, lower the pH. Roots in general release ions that match what they are taking in. Urea metabolites are acidic so h+ is released and over time the soil pH lowers. Soil bacteria at warmer temperatures break the urea down, uptake of ammonium over long term can lead to lower ph. There is a wealth of more specific info on the web
So flushing or leaching with clear water can help to alleviate the up or down change in pH in soils and media, depending on the type of fertilizer being used, soil type and water alkalinity

 

[DarioU]

Thank You

 

[Ray]

Keep in mind that this discussion pertains more to *soil* than to orchid media.