Objectives The periodical change trend of arable land fertility reflects the outcome of fertilization practices. So we studied the change of soil fertility in recent four decades in Guanzhong area for sustainable agriculture.
Methods We collected the published data from 1980 to 2020, the data from the Second Soil Census in 1980s, and the measured data by ourselves in Shaanxi Province, including soil organic matter (SOM), total nitrogen (TN), alkaline hydrolyzed nitrogen (AN), total phosphorus (TP), Olsen-P (AP), total potassium (TK), available potassium (AK), pH, and bulk density at topsoil layer. The change in soil fertility was summarized in 10-years scale, and compared among the four periods.
Results From 1980 to 2020, using every 10-year as a group, the median values of SOM content in the four groups were 11.0 g/kg, 11.1 g/kg, 13.6 g/kg and 18.5 g/kg, respectively, with a significant higher increase in the latter two decades than the early two decades. The median TN content in the four ten-year groups was 0.77 g/kg, 0.81 g/kg and 0.81 g/kg, 0.95 g/kg, with the significantly higher TN in the latest ten-year than in the other three groups. The median content of AN in 2011−2020 (58 mg/kg) was significantly higher than in the first 20 years. The median TP content in the four groups were0.70 g/kg, 0.76 g/kg, 0.82 g/kg and 1.03 g/kg, respectively, with a significant increasing trend. The median AP content in 2011−2020 was 21.9 mg/kg, which was significantly higher than those in the first three groups (8.5 mg/kg, 8.5 mg/kg and 18.7 mg/kg), and 80% of the data exceeded the agronomic threshold of AP (14 mg/kg) in the last 10 years. The median TK contents in the four groups were 19.3 g/kg, 19.9 g/kg, 18.6 g/kg and 19.6 g/kg, respectively, and not significantly varied. The median AK content was 212 mg/kg in 2011−2020, which was significantly higher than those in the first three groups (163 mg/kg, 149 mg/kg, 158 mg/kg). The median value of soil pH during 2011−2020 (7.76) decreased significantly compared with the first three groups (8.10, 7.90 and 8.00). The median soil bulk density in the four groups was similar.
Conclusions In the Guanzhong region of Shaanxi Province, the SOM, TN, TP, AP and AK increased, while the pH decreased significantly from 2001 to 2020, compared with those from 1980 to 2000. In conclusion, long term fertilization would not impact soil bulk density, but could increase the organic matter and total N and P storage, enhance the availability of N, P and K nutrient due to the decrease of soil pH. Modifications in nutrient management and tillage system should be studied for the culture of fertile farmland.
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