Substrate-Induced Organic Phosphorus Mineralization

Phosphatase activities in soils and surface waters have been linked to organic phosphorus mineralization, which is regulated by enzymatic hydrolysis by microbes. To determine the enzymatic activities of ambient microbial populations, field moist samples are spiked with nonlimiting concentration of LOP and incubated for a period of 2 h, followed by extraction of soils with 0.5 M NaHCOj. Soil suspensions are filtered through a 0.45 pm membrane filter and analyzed for DRP 

FIGURE 9.54 Substrate induced organic phosphorns mineralization in northern Everglades wetland soil. (From Chua, 2000.) 

In addition to mineralization of organic phosphorus, microbial decomposition of detrital matter and soil organic matter can have indirect effect on phosphorus solubility, as described below  

Anaerobic decomposition of organic matter and detritus can result in production of organic acids, which can result in solubilization of phosphorus bound to iron, aluminum, calcium, and magnesium. 

Organic anions produced during decomposition can compete with phosphate ions for adsorbing surfaces, thus decreasing phosphorus retention. 

---

Mineralization of added organic substrates Substrate-induced organic phosphorus mineralization (SIPM)... 

Substrate-induced phosphorus mineralization (SIPM) can indicate activity of microbes and associated enzymes involved in organic phosphorus mineralization. Hydrolysis of added substrates such as glucose-6-phosphate was not influenced by P enrichment in the litter layer (Chua, 2000). In the 0-10 cm soil layer, substrate hydrolysis decreased by approximately 67% at the impacted site. The mineralization coefficient (SIPM/MBP) also decreased by 54 and 74% in the litter and 0-10 cm soils, respectively, at the impacted site. These decreases suggest that phosphorus is not limiting to microbes. High substrate phosphorus hydrolysis at the reference site was attributed to limitation of labile inorganic phosphorus and high phosphatase activity. 

---