【Objective】 Soil potassium is an essential macronutrient for crop growth and plays a key role in maintaining high crop yield. However, so far it is still unclear as to dynamics of soil potassium utilization, especially quantitative relationships of content of soil readily available K with input of extraneous and budgeting of cumulative soil potassium relative to fertilization method. Therefore, this study was oriented to analyze dynamics of crop K uptake, crop K recovery rate, soil K budgeting and content of soil readily available K and to explore quantitatively relationships of soil readily available K with input of extraneous K and budgeting of cumulative soil K relative to fertilization practice based on a long-term fertilization field experiment in a field of vertisol in North China.【Method】The long-term experiment, located at the Mengchen Agro-Ecological-Station in the Huang-Huai-Hai Plain, North China, was initiated in 1982 and designed to have five treatments, i.e., CK (no fertilizer), CF (mineral fertilizers), SCF (mineral fertilizers plus wheat straw), PCF (mineral fertilizers plus pig manure), and CCF (mineral fertilizers plus cattle manure), and four replicates for each. Plots, 70 m² each in area, of the treatments and replicates were laid out in a randomized block design and separated from each other with cement boards embedded 50 cm deep. Soil samples were collected randomly from the top 20 cm soil layer of each plot along a S-shaped line, after the crop of soybean was harvested in October each year, with a soil core sampler (inner diameter 7 cm). Chemical N, P and K fertilizer was applied in the form of urea, calcium superphosphate and potassium chloride, respectively, at a rate the same as the local farmers did, i.e., 180 kg N, 39.3 kg P, and 112 kg K hm^-2 yr^-1. Soil total K was measured with the sodium hydroxide melting - flame photometry, soil slowly available K with the nitric acid boiling - flame photometry, soil readily available K with the ammonium acetate extraction - flame photometry and crop K with the vitriol peroxide/hydroxidation - flame photometry. 【Result】 It was found that the mean crop K recovery rate varied in the range of 55.1% ~ 66.1%, relative to treatment and displaying an order of CCF > PCF > SCF > CF. The content of soil readily available K increased somewhat in all the treatments except in CK, where the content declined steadily over time. The over-year mean content of soil readily available K exhibited an order of CCF (289.5 mg kg^-1) > PCF (133.0 mg kg^-1) > SCF (128.4 mg kg^-1) > CF (82.4 mg kg^-1) > CK (72.3 mg kg^-1). On the whole, a significant (p< 0.05) positive linear relationship was observed between soil K budgeting and content of soil readily available K. The gain of each 100 kg hm^-2 in soil K budgeting raised the content of soil readily available K in Treatment CF, SCF, PCF, and CCF by 1.4 mg kg^-1, 1.8 mg kg^-1, 2.3 mg kg^-1 and 15.8 mg kg^-1, respectively. Besides, a significant (p < 0.05) positive linear relationships between input of soil K and content of soil readily available K was also observed in all the fertilization treatments. The input of each 100 kg hm^-2 increased the content of soil readily available K by 0.4 mg kg^-1, 0.5 mg kg^-1, 0.6 mg kg^-1 and 4.3 mg kg^-1 in Treatment CF, SCF, PCF, and CCF, respectively. Compared to the increase in Treatment CF, that in the treatment amended with organic material (wheat straw, pig manure or cattle manure), that is, Treatment SCF, PCF and CCF was 25%, 50% and 975% higher, respectively, which indicates that application of a proper rate of organic material may improve soil K supply capacity in soils the same in input of extraneous K and soil K budgeting. 【Conclusion】To sum up, application of organic material is an important practice regulating soil potassium utilization. Long term application of organic manure, especially cattle manure in the study, may increase crop potassium recovery rate and transformation rate of surplus soil K into readily available K. Therefore, the application of animal-digested crop straw is a recommended practice to achieve stable and high crop yields in fields of vertical under wheat-soybean cropping system in North China.