3.3 Total N, available P and available K in soils
Contents of soil total N, available P and available K in the two counties increased, and the increase was higher in Meixian County (Fig. 4). Total N in soils of Wugong and Meixian counties increased from 0.8 g kg-1 and 0.9 g kg-1 in 1980 to 0.95 g kg-1 and 1.21 g kg-1 in 2017, respectively. Available P in Wugong County increased 3.1 times from 9.6 mg kg-1 in 1980 to 30 mg kg-1 in 2017, whereas in Meixian County, available P increased from 4.9 mg kg-1 in 1980 to 111 mg kg-1 in 2017. Available K in Wugong County increased slowly from 1980 to 2017, from 112 mg kg-1 to 159 mg kg-1. For Meixian County, the available K increased rapidly, from 107 mg kg-1 to 509 mg kg-1.