Abstract:

The easy fixation of phosphorus fertilizer in soil is a main reason for the low utilization rate of phosphorus fertilizer. In order to study the effects of fertilization frequency on availability of phosphorus fertilizer， three cinnamon soils with different Olsen-P levels （19.4， 24.2， 49.7 mg·kg^-1） were collected in the long-term fertilization test based on Shouyang County， Jinzhong City Shanxi Province， and the same amount of phosphorus fertilizer （potassium dihydrogen phosphate） was added to the soil with different Olsen-P levels by once and 3 times， respectively. The soil with Olsen-P was incubated under constant temperature condition for 90 d， soil Olsen-P content was measured by 11 sampling intervals， and the phosphorus forms in soil were measured at the end of incubation. The effects of fertilization frequency on soil Olsen-P content， phosphorus fixation rate and phosphorus forms were analyzed， and characteristics on availability of phosphorus fertilizer under different fertilization times were clarified. The results showed that after 90 d of fertilization， the soil Olsen-P contents under 3 times of application increased significantly compared with that of once of application， and the increase rates at 3 Olsen-P levels were 21.0%， 13.5% and 9.4%， respectively. However， the phosphorus fixation rate decreased significantly， which were 8.0%， 6.8% and 10.5% at 3 Olsen-P levels， respectively. The Michaelis-Menten equation betterly fitted the process of soil phosphorus fixation. The maximum phosphorus fixation rate of once application was greater than that of 3 times application， but the time to reach 50% of the maximum phosphorus fixation rate was shorter than that of 3 times application. The phosphorus fixation rate decreased with the increase of Olsen-P levers under once application. Phosphorus fixation rate in high Olsen-P （49.7 mg·kg^-1） soil was significantly reduced by 10.8%～12.4% compared with low Olsen-P （19.4～24.2 mg·kg^-1） soil under 3 times application.When compared with once application， the content of labile P in soil increased by 6.8%～12.1%， and the content of non labile P decreased by 8.4% under 3 times application. This study showed that the 3 times application of phosphorus fertilizer could significantly improve the availability of soil phosphorus and reduce the fixation rate of phosphorus fertilizer； the higher soil Olsen-P content was， the smaller the proportion of phosphorus fertilizer was invalidated in soil； the 3 times application of phosphorus fertilizer could increase soil Olsen-P content， decrease phosphorus fixation rate and increase the content of labile P. These results had important directive significance to improve the utilization rate of phosphorus fertilizer， and provided theoretical basis for efficient and scientific application of phosphorus fertilizer.

Key words: P-fixation, multiple application, dynamics equations, Olsen-P level, phosphorus forms

摘要：

磷肥在土壤中易被固定是磷肥利用率低的主要原因，为研究施肥次数对磷肥有效性的影响，依托山西省晋中市寿阳县长期施肥试验基地，采集3个不同有效磷（Olsen-P）水平（19.4、24.2、49.7 mg·kg^-1）的褐土，将等量的磷肥（磷酸二氢钾）1次与分3次分别添加到不同Olsen-P水平的土壤中，恒温培养90 d，间隔取样11次测定土壤Olsen-P含量，培养结束后测定土壤磷形态，分析施肥次数对土壤有效磷含量、固磷率和磷形态的影响，解析不同施肥次数下磷肥有效性的差异特征。结果表明，施肥90 d后，磷肥分3次施用的土壤Olsen-P含量比1次施用显著增加，在3个Olsen-P水平增加率依次为21.0%、13.5%和9.4%；而磷肥固定率则显著降低，在3个Olsen-P水平降低率依次为8.0%、6.8%和10.5%。米氏方程能更好地拟合土壤对磷的固定过程，磷肥1次施用的最大固磷率大于分3次施用，但达到最大固磷率50%的时间短于分3次施用。磷肥1次施用下，磷的固定率随Olsen-P水平增加而降低；分3次施用下，在高Olsen-P水平（49.7 mg·kg^-1）的土壤上，磷的固定率比低Olsen-P水平（19.4～24.2 mg·kg^-1）的土壤显著降低了10.8%～12.4%。与磷肥1次施用相比，磷肥分3次施用的土壤活性态磷含量增加了6.8%~12.1%，土壤稳定态磷含量则降低了8.4%。本研究表明，磷肥分3次施用可显著提升土壤磷的有效性、降低磷肥固定率；土壤Olsen-P水平越高，磷肥被土壤固定的数量和比例越小；磷肥分3次施用能提升土壤Olsen-P含量、降低磷肥固定率、提高活性磷含量。结果对提高磷肥的利用率具有重要指导意义，为磷肥高效利用和科学施用提供了理论依据。

关键词: 磷的固定, 多次施用, 动力学方程, Olsen-P水平, 磷形态