Temporal-spatial variability of soil available phosphorus and potassium in the alluvial region of the Huang-Huai-Hai Plain

The temporalspatial variability of available phosphorus (AP) and available potassium (AK) was studied by the analysis of their changes in the arable layers of the 124 sampling sites in the alluvial region of the HuangHuaiHai Plain, Quzhou county, Hebei province from 1980 to 2000 The results indicated that the average content of AP and AK in the county was 8.8 mg/kg and 90.0 mg/kg in 2000, 69.2% higher and 46.1% lower, respectively, than that in 1980 It is worthwhile noting that the content of AP and AK in 31% and 92% of the arable land of the county, respectively, decreased in a period of twenty years During the period, AP of fluvoaquic soil, saline soil, and cinnamon soil increased by 3.5 mg/kg, 5.8 mg/kg, and 4.5 mg/kg, and their AK decreased by 80.1 mg/kg, 30.4mg/kg, and 39.0mg/kg, respectively Key words: HuangHuaiHai Plain; plowed layer of soil; available phosphorus; available potassium; temporalspatial variability