Integrated field assessment of nitrogen release dynamics and crop recovery of band-applied controlled-release fertilisers

Purpose To conduct a field-based, integrated assessment of the effect of band-applied, polymer-sulfur coated urea (PSCU), plant oil coated urea (POCU), and polymer coated urea (PCU) on (i) the release dynamics of urea-N and mineral N in the soil profile (Experiment 1); and (ii) the crop N recovery and agronomic response of an irrigated maize crop (Experiment 2) relative to standard urea. Methods Two experiments were conducted in a Vertosol under subtropical field conditions. In both experiments, six treatments (nil, urea, PSCU, POCU, and two PCU products) were replicated four times. Soil samples were collected at 8, 27, 48, 82 and 173 days after fertiliser application (DAF) to quantify N release dynamics. Maize biomass production, N uptake, grain yield and N content were quantified to assess the agronomic performance of CRFs relative to standard urea. Results CRFs delayed the release of N relative to standard urea. Soil moisture and mass flow impacted N release dynamics from fertiliser bands, with soil chemical changes largely confined to the band for CRFs. Despite obvious differences in N release dynamics, there were no clear advantages of CRFs relative to standard urea for crop productivity and grain yield. A significant amount of in-season mineralization likely masked any potential benefits arising from the slower release of N from CRF products. Conclusion This study improves our understanding of how CRFs behave in soil under changing environmental conditions and highlights the complexity of synchronizing N supply and crop N requirements to improve NUE in irrigated maize.

Automated summary

The study found that controlled-release fertilizers can delay nitrogen release compared to standard urea, but do not show clear advantages in terms of crop productivity and yield. Despite differences in nitrogen release dynamics, in-season mineralization may mask any potential benefits from the slower release of nitrogen from controlled-release fertilizer products.