Feeding the World While Healing the Planet
Exploring nitrogen management challenges and solutions in China's intensive wheat-maize agricultural system
Imagine a world where the very substance that helps grow the food on your plate also slowly degrades the environment around you. This is the double-edged sword of nitrogen, a chemical element essential to all life that has become one of modern agriculture's greatest challenges and opportunities.
The core challenge in China's nitrogen management can be summarized in one stark statistic: while research trials demonstrate that nitrogen use efficiency (NUE) can reach 26-28%, the actual efficiency in farmers' fields is dramatically lower at just 16-18% 2 .
This inefficiency comes with staggering numbers. In the intensive wheat-maize system, typical nitrogen application rates exceed 500 kg per hectare annually, approaching 600 kg in some regions 2 .
When nitrogen is applied to crops but not used efficiently, it doesn't just disappear—it finds its way into our environment through multiple pathways. At the national scale in China's wheat systems, applied nitrogen partitions into approximately 41.56% uptake by the plants, 29.66% residual in the soil, and 38.81% lost to the environment 1 .
| Nitrogen Pathway | Percentage (%) | Environmental Impact |
|---|---|---|
| Plant Uptake | 41.56 | Productive use |
| Soil Residual | 29.66 | May contribute to future losses |
| Total Losses | 38.81 | Cumulative environmental damage |
| Â Â - Ammonia (NH3) | 9.35 | Air pollution, particulate formation |
| Â Â - Leaching | 7.38 | Groundwater contamination, eutrophication |
| Â Â - Runoff | 4.68 | Surface water pollution |
| Â Â - Nitrous Oxide (N2O) | 0.73 | Greenhouse gas emissions |
| Â Â - Nitric Oxide (NO) | 0.38 | Air pollution |
One of the most fascinating aspects of China's nitrogen management story is how dramatically the challenges and solutions vary across different regions. Research has revealed that nitrogen fate follows a distinct geographical pattern, with uptake increasing from north to south, while residual nitrogen and losses gradually decrease 1 .
Ammonia volatilization accounts for a striking 91.76% of total nitrogen loss 1 .
Ammonia volatilization
Loss pathways are more balanced, with ammonia constituting 53.45% of losses and leaching accounting for 41.38% 1 .
Ammonia volatilization
Leaching
Shows the most even distribution of losses across multiple pathways 1 .
Multiple pathways
| Region | Dominant Loss Pathway | Percentage | Recommended Focus |
|---|---|---|---|
| Northern China | Ammonia (NH3) volatilization | 91.76% | Loss reduction |
| Central China | Ammonia volatilization | 53.45% | Residual management |
| Leaching | 41.38% | ||
| Southern China | Multiple pathways | Distributed | Loss reduction |
At the core of these solutions are the 4R principles: applying the right fertilizer source at the right rate, right time, and right place 4 .
When implemented effectively, these principles have shown remarkable results. For instance, site-specific nitrogen management, as part of 4R practice, has been demonstrated to reduce nitrogen fertilizer use by 32% while simultaneously increasing yields by 5% in China 4 .
While improved field management practices are essential, researchers are increasingly recognizing that truly sustainable nitrogen management requires thinking beyond individual fields to the entire food chain. A new framework called food-chain-nitrogen-management (FCNM) has been proposed to address nitrogen flows from production to consumption 4 .
Reduce the need for synthetic fertilizers
Better nutrient synchronization
Reduce nitrogen-intensive food consumption
Across the entire food system
Reduction in nitrogen fertilizer usage
Decrease in nitrogen-induced water pollution
Reduction in agricultural water consumption
These changes could result in national societal gains of around US$140 billion against a net investment of just US$8 billion 6 .
To understand how scientists are developing and testing improved nitrogen management practices, let's examine a comprehensive field experiment conducted across multiple locations in Shandong province between 2016 and 2020 5 .
The researchers established experiments in four cities in Shandong province (Jining, Dezhou, Yantai, and Zibo), representing different ecological conditions within the North China Plain 5 .
The results of this multi-site experiment were striking. Compared to the common farmer practice, the high-yield and high-efficiency approach (HHL) increased yields by 13.7% while boosting partial factor productivity of nitrogen (PFPN, an important efficiency metric) by an impressive 58.2% 5 .
| Management Approach | Yield Change | Nitrogen Efficiency (PFPN) Change | Key Physiological Improvements |
|---|---|---|---|
| High-Input Level (HIL) | +22.0% | +8.4% | Not specified |
| High-yield & High-efficiency Level (HHL) | +13.7% | +58.2% |
Tiller survival: +19.8% Tiller coefficient: +33.3% Post-anthesis biomass: +7.4% Biomass remobilization: +33.1% |
| Research Term | Definition | Significance |
|---|---|---|
| Nitrogen Use Efficiency (NUE) | The proportion of applied nitrogen recovered in harvested crop | Measures how effectively crops utilize fertilizer |
| Partial Factor Productivity (PFPN) | Crop yield per unit of applied nitrogen | Important indicator of economic and environmental efficiency |
| Recovery Efficiency (REN) | The proportion of nitrogen fertilizer taken up by the crop | Direct measure of plant uptake efficiency |
| Nitrogen Nutrition Index (NNI) | A quantitative method for diagnosing crop nitrogen status | Helps determine optimal nitrogen application timing and rates |
| Nitrogen Balance/Budget | The difference between nitrogen inputs and outputs in a system | Identifies nitrogen surpluses (risk of loss) or deficits (soil mining) |
Looking ahead, research points to several promising directions for advancing nitrogen management in China and beyond. The concept of the food-energy-water nexus highlights how nitrogen management intersects with these three critical resources 6 .
Another promising frontier is the development of climate-adaptive sustainable agricultural systems 7 . As climate change increases yield variability and extreme weather events, nitrogen management strategies must become more resilient and flexible.
Research combining field experiments with crop modeling suggests that efficient agronomic practices could enhance wheat yields by about 7-14% without expanding cultivation areas in China 7 .
A 35-year study of the paddy rice-upland wheat cropping system found that combining mineral fertilizers with organic manure produced higher yields than either approach alone .
Recommended annual application
Mineral & organic sources
The challenge of nitrogen management in China's wheat-maize systems represents a microcosm of the broader global dilemma of how to meet human needs while respecting planetary boundaries. The current situation, characterized by overuse and inefficiency, is not sustainable—but the research we've explored demonstrates that viable alternatives exist.
As consumers, policymakers, and citizens, we all have a role to play in supporting this transition. Whether through our food choices, support for agricultural research, or policies that incentivize sustainable practices, we can contribute to a future where nitrogen no longer represents an environmental threat but instead becomes a well-managed resource that helps feed the world sustainably.