Much remains unknown regarding the behaviour of P in cropping soils. We have examined a low-input long-tern cropping system not receiving P fertilizers in subtropical Queensland (Australia) in order to determine how, after 50 y, P concentration and distribution in bulk soils and in soil aggregates is affected by tillage practices (no tillage [NT] and conventional tillage [CT]) and by N fertilization. For the bulk soil, neither the tillage practice nor N fertilization altered concentrations of total P, inorganic P (P_i), or organic P (P_o) despite soil organic C concentrations differing significantly depending upon both tillage and N fertilization. Although bulk concentrations of P did not differ significantly, we observed significant changes in NaHCO₃-P_i, 1 M HCl-P_i, NaOH-P_i, NaOH-P_o determined using sequential extraction, seemingly due to changes in pH associated with N fertilization. We also used sequential fractionation to examine the forms of P in the various water-stable aggregate sizes, finding that the tillage practices and N fertilization did not cause significant changes in either the distribution of the various aggregate sizes nor did it cause marked changes in the forms of P in these various aggregates. Thus, our data illustrate that even though the long-term usage of NT in low-input soils may cause a comparative increase in TOC, there was not a concomitant increase in P_o, with this being important for soil fertility and functioning. This information assists in understanding how management practices alter P behaviour in long-term, low-input subtropical cropping soils, as is required to manage these soils more appropriately.

关于磷在耕作土壤中的行为，仍然有许多未知数。我们已经研究了在亚热带昆士兰州（澳大利亚）不接受磷肥的低投入长期种植系统，以确定在耕种50年后，耕作方式如何影响散装土壤和土壤团聚体中磷的浓度和分布（无耕作[NT]和常规耕作[CT]）并通过氮肥施肥。对于大块土壤，尽管土壤有机碳的浓度取决于耕种和施氮量，但耕作习惯和氮肥均不会改变总磷，无机磷（P _i）或有机磷（P _o）的浓度。尽管P的总浓度没有显着差异，但我们观察到NaHCO ₃ -P的显着变化_i，1 M HCl-P _i，NaOH-P _i，NaOH-P _o使用连续萃取法测定，似乎是由于与氮肥相关的pH值变化。我们还使用顺序分级法研究了各种水稳性团聚体大小中P的形式，发现耕作方式和氮肥施肥既不会导致各种团聚体大小的分布发生显着变化，也不会引起土壤中显着变化。这些不同聚集体中的P形式。因此，我们的数据表明，即使在低投入土壤中长期使用NT可能会导致TOC相对增加，但P _o并没有随之增加。，对于土壤肥力和功能至关重要。这些信息有助于理解管理实践如何改变长期，低投入的亚热带作物土壤中的P行为，这是更适当地管理这些土壤所需要的。