What question did this study set out to answer?

The study aims to assess how different nitrogen application rates affect garlic yield and nitrogen use efficiency.

February 2, 2026Open Access

Effects of Nitrogen Application Rate on Bulb Yield, Nitrogen Use Efficiency, and Normalised Difference Red Edge-Based Nitrogen Diagnostics in Garlic Varieties

BNBinh T. NguyenThe University of Queensland JWJ. Bernhard WehrThe University of Queensland TOT.J. O’HareThe University of Queensland

Key Points

The study aims to assess how different nitrogen application rates affect garlic yield and nitrogen use efficiency.
Conducted a field experiment with nine nitrogen rates (0–360 kg N ha−1) across three garlic varieties.
Measured foliage and bulb nitrogen concentrations at key growth stages.
Collected NDRE data at 147 days after planting to evaluate nitrogen status and yield.
Determined yield components at 185 days after planting.
Bulb yield increased significantly with nitrogen rates, peaking at 160–240 kg N ha−1.
Higher nitrogen application reduced both dry matter content and nitrogen use efficiency.
NDRE values correlated highly with nitrogen rates, leaf nitrogen concentration, and bulb yield, indicating their efficacy as indicators.

Abstract

Optimising nitrogen (N) management is crucial for improving garlic (Allium sativum L.) productivity and nitrogen use efficiency (NUE). This study evaluated the effects of N application rate on bulb yield, NUE, and the links between N status, Normalised Difference Eed Edge (NDRE), and yield. A field experiment was conducted using nine N rates (0–360 kg N ha−1) across three garlic varieties (Glenlarge, Southern Glen and AV08). Foliage and bulb N concentrations were measured at key growth stages, and yield components were determined at 185 days after planting (DAP). NDRE values were collected at 147 DAP to evaluate their potential as non-destructive indicators of crop N status and yield. Nitrogen rate significantly affected bulb yield, with maximum yield achieved at 160–240 kg N ha−1. Increasing the N application rate reduced dry matter content and NUE across three garlic varieties. NDRE showed strong positive correlations with N rate (r2 = 0.96), leaf N concentration (r2 ≥ 0.82), and bulb yield (r2 = 0.85), demonstrating its sensitivity to in-season N variability and its potential for yield prediction. This study provides a systematic assessment of NDRE for N status diagnosis in garlic and presents initial evidence of varietal differences in N response, contributing to improving the understanding of management in this crop.

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