Regulation of soil fixed ammonium and soluble N through combined application of N fertilizer and manure

Objectives As the temporary storage pools of fertilizer nitrogen (N), soil fixed ammonium (FA) could subsequently release N for plant uptake. Soil soluble N (SSN-soil soluble organic N, SSON; soil mineral N, SMN) are the important sources of soil FA, therefore, it is imperative to study the effects of combined application of N fertilizer and manure on the dynamics of soil FA and soil soluble N and their relationship under the greenhouse cultivation.

Methods N application rates of: 0, 187.5, 375.0 and 562.5 kg/hm²(recordered as N0, N1, N2 and N3), 75000 kg/hm² of manure fertilizer combined with N0, N1, N2, and N3 were sep up in a field plot experiment under the greenhouse cultivation.

Results Fertilizer application significantly increased SSN and FA in the 0-30 cm depth (P < 0.01). In general, N2 treatment demonstrated the highest values for SMN, SSON and FA under no manure treatments. MN2 and MN3 treatments had the highest values for SMN, SSON and FA under the N fertilizer and manure combined application. There were no significant differences for soil FA with different nitrogen fertilizer rates (P > 0.05). Soil FA was significantly and positively correlated with SMN during the growing season, except for 20-30 cm interval during the harvesting period (P < 0.05). Significant and positive correlation was also existed between soil FA and SSON in some soil layers (P < 0.05).

Conclusion Soil fixed ammonium and soluble N pools significantly affect the N immobilization and release. The appropriate rate of N fertilizer and manure application (M: 75000 kg/hm²; N2: 375.0 kg/hm²) could modulate the soil N supply more effectively in greenhouse cultivation.