Establishing critical nitrogen dilution curves based on leaf area index and aboveground biomass for greenhouse cherry tomato: A Bayesian analysis

Intensification of greenhouse production is always closely related to massive nitrogen (N) losses to the environment. Therefore, precisely assessing crop N status and optimizing N fertilizer management are essential for the sustainability of greenhouse system. The study was endeavored to (1) assess whether the parameters of critical nitrogen (Nc) dilution curves were significantly affected by the irrigation level, and (2) compare if both leaf area index (LAI) and aboveground biomass (AGB) based Nc dilution curves could accurately diagnose cherry tomato N status using a recent Bayesian statistical approach. A three-year greenhouse cherry tomato experiment containing five N levels (0, 180, 270, 360 and 450 kg N ha⁻¹) and three irrigation levels (60 %, 80 % and 100 % ET₀, where ET₀ was the reference evapotranspiration) was conducted from 2019 to 2021. The width of the 95 % credibility intervals of Nc dilution curves based on AGB and LAI decreased with the increasing AGB and LAI. Taking the 95 % credibility intervals of parameters A1 and A2 into consideration, water availability of 60 %–100 % ET₀ had no significant effect on AGB-based Nc dilution curves in 2019 and 2021, and it also had no significant effect on LAI-based Nc dilution curves during 2019–2021. Delaying the transplanting date of greenhouse cherry tomato would significantly decrease parameter A1, while parameter A2 was not affected. The differences of nitrogen nutrition index (NNI) calculated from the AGB- and LAI-based Nc dilution curves were negligible under different irrigation levels and sampling dates. The maximum relative yield was associated with an NNI of 0.99 for both AGB and LAI. These results indicate that Nc dilution curves established based on both AGB and LAI could precisely diagnose cherry tomato N status. There is no need to establish specific Nc dilution curves for greenhouse cherry tomato under non-extremely water-stressed conditions.