Optimizing nitrogen management in grain rotations: balancing retention and photosynthesis

Area of Science:

• Agricultural Science
• Agronomy
• Soil Science

Background:

• Diversified cropping systems enhance resource use, but nitrogen (N) dynamics in economic-grain rotations are unclear.
• Understanding N allocation and utilization is crucial for optimizing multi-cropping systems.

Purpose of the Study:

• Investigate cross-seasonal N allocation and photosynthetic responses to N reduction in a garlic-maize rotation.
• Determine optimal N management strategies for balancing productivity and economic returns.

Main Methods:

• Conducted a three-season field experiment with graded N treatments for garlic and maize.
• Measured soil properties (WFPS, NO3--N), leaf physiological parameters (LAI, SPAD, photosynthesis), and yield components.
• Analyzed N partitioning, translocation, and efficiency metrics (NUE, agronomic efficiency).

Main Results:

• Nitrogen reduction increased soil WFPS during maize but decreased it in garlic seasons, and reduced topsoil nitrate accumulation.
• Leaf physiological parameters declined under N reduction, with garlic showing higher sensitivity.
• Maize achieved optimized grain N partitioning and improved NUE with N reduction, showing compensatory inter-season adjustments from residual N.
• Garlic exhibited increased stem N translocation and decreased bulb allocation under N reduction.
• Annual N reduction enhanced maize agronomic efficiency but reduced garlic yields and partial factor productivity.

Conclusions:

• Garlic-maize rotation systems display contrasting, crop-specific N allocation strategies.
• Demand-driven N management is essential for optimizing productivity and economic outcomes in diversified cropping systems.