This study was under the long-term fertilization in black soil (harbin), which had 24 treatments from the year of 1979, under the rotation of wheat-soybean-corn, investigated the changes of black soil fertility under long-term fertilization, results showed that:
Soil organic matter (SOM) had big changes under different fertilization about 31 years. The content of SOM under no fertilizer (CK) decreased from 26.6 g/kg to 22.3 g/kg, about 16.2%; the treatment of chemical fertilizer (NPK) also made the SOM ...