Readily available chemical fertilizers have resulted in a decline in the use of organic manure (e.g., green manures), a traditionally sustainable source of nutrients. Based on this, we applied urea at the rate of 270 kg ha⁻¹ with and without green manure in order to assess nitrogen (N) productivity in a double rice cropping system in 2017. In particular, treatment combinations were as follows: winter fallow rice-rice (WF-R-R), milk vetch rice-rice (MV-R-R), oil-seed rape rice-rice (R-R-R) and potato crop rice-rice (P-R-R). Results revealed that green manure significantly (p ≤ 0.05) improved the soil chemical properties and net soil organic carbon content increased by an average 117.47%, total nitrogen (N) by 28.41%, available N by 26.64%, total phosphorus (P) by 37.77%, available P by 20.48% and available potassium (K) by 33.10% than WF-R-R, however pH was reduced by 3.30% across the seasons. Similarly, net dry matter accumulation rate enhanced in green manure applied treatments and ranked in order: P-R-R > R-R-R > MV-R-R > WF-R-R. Furthermore, the total leaf dry matter transport (t ha⁻¹ ) for the P-R-R in both seasons was significantly higher by an average 11.2%, 7.2% and 36 % than MV-R-R, R-R-R, and WF-R-R, respectively. In addition, net total nitrogen accumulation (kg ha⁻¹ ) was found higher in green manure applied plots compared to the control. Yield and yield attributed traits were observed maximum in green manure applied plots, with treatments ranking as follows: P-R-R > R-R-R > MV-R-R > WF-R-R. Thus, results obtained highlight ability of green manure to sustainably improve soil quality and rice yield.

Soil organic carbon; dry matter; nitrogen accumulation; milk vetch; rapeseed