Quantifying the timing asynchrony between soil nitrogen availability and maize nitrogen uptake

Abstract

Background and aims

In temperate annual cropping systems, an asynchrony between soil inorganic nitrogen (N) availability and plant N uptake is hypothesized to be a major source of poor N fertilizer use efficiency and environmental N losses. However, relationships between the timing of plant N uptake and soil N availability are poorly understood due to a lack of high-resolution time-series measurements.

Methods

We measured soil inorganic N pool size from 0–30 cm and 30–60 cm as well as maize (Zea mays) N uptake at high temporal resolution throughout the growing season across nine site-years. Using these data, we developed models based on growing degree days (GDDs) to quantify the asynchrony between soil N pool size and crop N uptake We used absolute values (kg N ha⁻¹) and standardized values as a percent of maximum soil and plant N pool sizes for each site-year.

Results

The maximum rate of maize N uptake lagged the maximum rate of soil inorganic N depletion by 91 and 185 GDDs for models of absolute and standardized data. By the cessation of maize N uptake, soil inorganic N pool size declined to < 20% of initial values (< 35 kg N ha⁻¹).

Conclusion

Our data provide a valuable resource to quantify and reduce asynchrony between soil N availability and maize N demand. The models developed herein can transfer across other locations. To improve N fertilizer management.