Nitrogen (N) addition and precipitation increment can greatly influence soil phosphorus (P) dynamics, with much emphasis on total and available P, yet little is known about their interactive effects on soil mineral‐bound inorganic P (P_i) fractions under different historical land uses of grasslands and old fields. Thus, we compared (i) plant readily available P, (ii) less available P_i (sum of NH₄F‐extractable P_i, NaOH‐Na₂CO₃‐extractable P_i and NaHCO₃‐extracted P_i), (iii) refractory forms of P_i (NH₄Ac‐extractable P_i, H₂SO₄‐extractable P_i and Na₃(citrate)‐dithionite‐extractable P_i) and (iv) organic P under the same urea and water treatments in an old‐field grassland with a semi‐arid steppe. Soil total P remained unchanged with 10‐year urea addition in both sites, with lower organic P but higher P_i concentrations in the old field. Urea addition promoted transformation of refractory P_i into less available P_i in both sites, which potentially was related to higher plant productivity and thus enhanced plant P accumulation. Specifically, urea addition increased less available P_i fractions by as much as 42%, but decreased refractory P_i fractions by as much as 24%, for two sites under ambient precipitation. Water addition decreased less available P_i in the steppe under higher urea addition rates, whereas it increased less available and refractory P_i but only in the control plot of the old field. Irrespective of urea and water treatments, the old field had a higher P_i pool, which could replenish plant readily available P in the longer term and be less prone to P‐limitation than the steppe. We conclude that conversion of semi‐arid steppe to farmland causes long‐term increases in the soil P_i pool, possibly by enhancing organic P mineralization and anthropogenic fertilization during cultivation. Urea addition accelerated soil P cycling via promoting refractory P_i, transforming into less available P_i, with the process being strongly mediated by water availability, whereas the projected precipitation increment could decrease less available P_i via promoting plant P uptake and P leaching out of the plant–soil system.

中文翻译：

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不同土地利用历史下半干旱草原尿素与水分的交互作用对土壤矿质磷动态的影响

氮（N）的添加和降水量的增加会极大地影响土壤磷（P）的动力学，重点在于总磷和速效磷，但对于不同历史时期它们对土壤矿物结合的无机磷（P _i）组分的相互作用的影响知之甚少。草原和旧田地的土地利用。因此，我们比较了（ⅰ）植物容易获得的P，（ⅱ）较少的可用P_我（NH的总和₄ F-提取磷_我，加入NaOH娜₂ CO ₃ -extractable P_我和NaHCO ₃ -extracted P_我），（ iii）难熔形式的P _i（NH ₄可萃取的P _i，H₂在相同的尿素和水处理条件下，在半干旱草原的老草原上，SO ₄可萃取的P _i和Na ₃（柠檬酸盐-亚硫联石可萃取的P _i）和（iv）有机P。在两个地点添加10年尿素后，土壤总磷保持不变，在旧田中有机磷含量较低，而P _i浓度较高。尿素的添加促进了耐火性P _i在两个部位转化为较少的可用P _i，这可能与更高的植物生产力相关，从而增强了植物P的积累。具体而言，添加尿素可使可用的P _i分数减少了多达42％，但降低了难处理的P对于环境降水下的两个地点，_我的分数高达24％。加水量下降较少有效磷_我在草原较高下添加尿素的价格，而这增加了少于可用，耐火材料P_我却只能在老油田的对照区。无论使用尿素和水处理方式如何，旧田的P _i池都较高，从长期来看，可以补充植物中容易获得的P，并且与草原相比，P限度较小。我们得出的结论是，半干旱草原向农田的转化会导致土壤P _i的长期增加可能通过增强耕作过程中有机磷的矿化作用和人为施肥来蓄水池。尿素的添加通过促进难处理的P _i加速土壤P的循环，转化为较少的可用P _i，该过程在很大程度上受到水的可利用性的调节，而预计的降水量增加可通过促进植物对P的吸收和P的淋溶而减少可用的P _i。植物-土壤系统。