Root and nitrate-N distribution and optimization of N input in winter wheat

Area of Science:

• Agronomy
• Soil Science
• Environmental Science

Background:

• Scientific nitrogen (N) fertilizer management is crucial for maximizing crop yield and minimizing environmental pollution.
• Understanding the interplay between soil nitrogen supply and crop nitrogen demand is key to efficient N fertilization strategies.

Purpose of the Study:

• To determine the relationship between soil N supply and N demand in winter wheat (Triticum aestivum L.) under varying N application rates.
• To identify optimal N input levels that balance wheat yield, nitrogen use efficiency (NUE), and environmental risks.

Main Methods:

• Conducted three-year field experiments at two sites in Henan Province, China, with N application rates ranging from 0 to 360 kg ha⁻¹.
• Analyzed aboveground N uptake, soil nitrate N (NO₃⁻-N) distribution with depth, and root weight density.
• Correlated N uptake and soil NO₃⁻-N with N application rates and root characteristics.

Main Results:

• Aboveground N uptake and soil NO₃⁻-N increased with N application, while NO₃⁻-N decreased with soil depth.
• Optimal correlations between N uptake and soil NO₃⁻-N were found in specific soil layers (20-60 cm and 20-80 cm) at different growth stages.
• Root weight density peaked at 90 kg N ha⁻¹, with significant distribution in the top 60 cm of soil, positively correlating with N uptake.
• Wheat yield saturated at high N rates (>270 kg ha⁻¹), leading to decreased NUE and increased residual soil NO₃⁻-N.

Conclusions:

• An N application rate of 180-270 kg ha⁻¹ is recommended for winter wheat in the study region under sufficient irrigation.
• This rate supports a well-developed root system, balances N supply and demand, and mitigates environmental risks associated with excessive N fertilization.