Evaluation of precision nitrogen management using leaf colour chart in lowland rice cultivation

Abstract

Blanket nitrogen recommendations waste fertiliser and pollute waterways. This research evaluated the leaf colour chart (LCC) as a real-time N management tool in lowland rice at the University of Hohenheim, Stuttgart, Germany (2021-2022). Five treatments were compared: fixed-rate 120 kg N ha⁻¹, LCC-guided at thresholds 3, 4, 5, and unfertilised control. LCC threshold 4 produced the highest yield (4,910 kg ha⁻¹) with only 105 kg N ha⁻¹, outperforming the fixed rate by 4.9% while saving 12.5% nitrogen. LCC-SPAD correlation was strong (R² = 0.87-0.91). Agronomic efficiency reached 18.7 kg grain per kg N under LCC-4 versus 13.0 under fixed-rate, confirming the LCC as a low-cost precision tool for temperate lowland rice.