A SIMPLE MODEL TO PREDICT N MINERALISATION OF GREENHOUSE SOILS

The formulation of a correct N fertilisation advice, besides a measurement of N_min at the start of the growing period, mainly depends on the possibility to predict the N mineralisation out of soil organic matter.
This study aimed to model the N mineralisation of greenhouse soils, using both easily available and easily measurable parameters.
Two laboratory incubation experiments were set up.
The first incubation experiment allowed to deduct a zero-order model, N_t = kt, in which N_t = N mineralised [kg N ha^-1], k = N mineralisation rate constant [kg N ha^-1 day^-1] and t = time [days], whereas the temperature dependence of the N mineralisation rate constant was deduced out of the second incubation experiment.
The N mineralisation rate constant further depends on the N mineralisation potential of the soil and on the ‘soil’s age’, i.e. being the time the soil has been glass-covered, eventually leading to the following simple N mineralisation model: Nt = (-9.965 + 0.104 NKCl + 0.336 T + 0.095 O)t, with NKCl = N_min in a hot KCl-extract (100°C) [kg N ha^-1], T = temperature [°C] and O = soil’s age [years].
Though the via the model calculated (k_mod) and experimentally obtained (k_exp) N mineralisation rate constants were closely related and a linear relationship was found k_mod = 0.872 k_exp (R² = 0.719, <0.01), further research is necessary to evaluate this model in-situ.
In the long run it will be incorporated into a nitrogen fertilisation advice system for greenhouse crops.

Workshop Towards and Ecologically Sound Fertilisation in Field Vegetable Production

J. Salomez, K. D’Haene, G. Hofman, I. Vandevelde

soil organic matter, incubation experiments, N mineralisation kinetics, rate constant

https://doi.org/10.17660/ActaHortic.2002.571.16