following the order of vegetable field > orchard > cropland
in the soil depths from 0 to 25 cm (Table 2). There
are no significant differences between orchard and vegetable
field. However, for the soil depths of 0–25 cm, the
TP contents in vegetable field are significantly higher
than that in the cropland. For the deeper soil layers
(40–70 cm), the TP is significantly higher in orchard
than that in the other two agricultural land use types (p <
0.05).
Following the same pattern as observed for the SOC
and TN, the TP contents in each agricultural land use
type decrease generally with soil depths increase, in particularly
in the soil profile of 0–40 cm (Table 2). Correspondingly,
the TP contents in the depths of 25–100 cm
range from 0.51 to 0.70 g/kg in these land use types.
The available phosphorus in vegetable field is the
highest (Table 3), corresponding well to the highest P
fertilizer inputs and frequent irrigation (Table 1). In the
depths from 0 to 40 cm, the available phosphorus contents
in vegetable field range from 22.03 mg/kg to 66.10
mg/kg which is about 2.5–6.5 times higher than those in
the other two agricultural land use types (Table 3). It is
presumed that high available phosphorus contents are
prone to potential risk of P loss and non-point source
pollution.
3.4 Soil nutrient absorption rate and soil nutrient
use economic efficiency ratio
Data of the agricultural land use economic outputs, plant
nutrient update, and input of fertilizers are shown in
Table 4. For different agricultural land use types, the
calculated values of nutrient absorption rate (NAR) and
nutrient use economic efficiency ratio (NEER) are listed
in Table 5. For both N and P, the NAR values in cropland
and vegetable field are higher than that in the orchard,
and the order is cropland > vegetable field > orchard.
Compared with P, the absorption rate of N is a
relatively higher in the three agricultural land use types.
The NARs in vegetable field and orchard are lower
than that in the cropland, and the NEERs show the op-