3.1 Nutrient inputs, outputs and surpluses
Nutrient inputs to croplands of the two counties have increased
gradually since 1992 (Fig. 2), with a greater increase in Meixian than
in Wugong County. In Wugong County, total N, P, and K increased from
303, 77, and 118 kg ha-1 in 1992 to 526, 136 and 240
kg ha-1 in 2017, with growth rates of 74, 77, and
103%, respectively. Whereas in Meixian County, total N, P, and K
increased from 464, 71, and 118 kg ha-1 to 887, 216,
and 552 kg ha-1, with growth rates of 91, 204, and
368%. Among various input sources, nutrients from synthetic fertilizers
are the main contributors. Nutrient outputs in the two counties over the
years remained relatively stable, resulting in high nutrient surpluses,
especially in Meixian County.