Runoff Losses of Nitrogen and Phosphorus in Double-Rice Cropping Systems Under Various Fertilizer Applications

Strategic Insights -

Research in Changsha, People's Republic of China, has shed light on the significant eutrophication risks posed by runoff losses of nitrogen (N) and phosphorus (P) from paddy fields. The study, which has been peer-reviewed, aimed to understand the long-term patterns of losses and mechanisms driving runoff N and P in double-rice cropping systems. The research found that optimizing fertilizer application and straw return to fields can minimize nitrogen and phosphorus runoff losses.

Key Takeaways:

  • The study revealed that the 0-20 days after fertilization was a high-risk period, contributing 41.7-56.6 % of annual TN and 20.2-25.8 % of TP loss loads.
  • Total nitrogen (TN) loss predominantly occurred during the early rice season (58.3-61.3 %), while TP loss is evenly distributed across the winter fallow and two rice seasons.
  • Optimized fertilization significantly decreased TN and TP losses by 11.7 % and 13.7 % compared with conventional fertilization.
  • The study concluded that understanding N and P losses patterns in subtropical double-cropping paddy fields with various agricultural management measures aids in assessing runoff water reuse potential, to achieve a virtuous cycle of water and nutrients.
  • The research was funded by the Natural Science Foundation of Hunan Province, Natural Science Foundation of Changsha City, Agricultural Science and Technology Innovation Funds Project of Hunan Province, and Postdoctoral Fellowship Program of CPSF.
  • The study was conducted over seven years, during which time total nitrogen (TN) and total phosphorus (TP) concentrations, TN and TP loss loads, grain yields, and soil fertility were continuously monitored.
  • The researchers selected typical subtropical double-cropped paddy ecosystems for observation.

Statistics:

  • 41.7-56.6% of annual TN loss loads occurred within 0-20 days after fertilization.
  • 20.2-25.8% of TP loss loads occurred within 0-20 days after fertilization.
  • 58.3-61.3% of TN loss occurred during the early rice season.
  • 11.7% of TN loss was reduced by optimized fertilization compared to conventional fertilization.
  • 13.7% of TP loss was reduced by optimized fertilization compared to conventional fertilization.

Sources:

  • NewsRx. Findings from Ministry of Agriculture and Rural Affairs in the Area of Rice Crops Described (Optimizing Fertilizer Application and Straw Return To Fields To Minimize Nitrogen and Phosphorus Runoff Losses In Double-rice Cropping Systems). Agriculture Week. August 7, 2025; p 1026.
  • Agricultural Water Management. Optimizing Fertilizer Application and Straw Return To Fields To Minimize Nitrogen and Phosphorus Runoff Losses In Double-rice Cropping Systems. 2025;317.