Phosphorus cycling within soil aggregate fractions of a highly weathered tropical soil: A conceptual model

Effective use of soil phosphorus (P) for crop production requires an understanding of how P pools are stabilized and cycled within soil aggregates, rather than assuming that P dynamics, particularly organic P, closely follow those of C. The main goal of this study was to compare C and N cycling with P dynamics in soil aggregate fractions under two distinct crop species, maize (Zea mays) and pigeon pea (Cajanus cajan) in a highly-weathered Lixisol. We found that while C and N follow an open cycle, whereby C and N are mineralized from microaggregates during macroaggregate turnover and partially exit the soil system as gas and leachate, P has a relatively closed cycle, where most of the mineralized and solubilized P from microaggregates is lost from the plant-available pool via sorption to the unaggregated silt and clay-sized particles (