The “N-C balance model” for optimizing nitrogen supply and temperature management in greenhouse fruit vegetable production

The N-C balance model is a growth model that describes how solar radiation, temperature and nitrogen supply affect the distribution of photosynthates (leaves, stems, fruits and roots), flower bud differentiation and flower number.
We focused on the fact that under conditions of sufficient fertilizer supply, the nitrogen content (N%) of each organ is almost constant and organ-specific, i.e., the N/C ratio has a constant relationship.
Conventional models describe the sink strength of each organ as a temperature-dependent function that accounts for the increase in the number of leaves and fruit ripening.
The N-C balance model is unique in that it assumes that the sink strength of each organ is not determined by temperature but by the amount of N distributed to that organ.
According to this model, an organ’s N demand is at first expressed as a function of temperature.
Next, the absorbed N is distributed in proportion to the N demand, while the necessary amount of C is then computed to ensure that the N content of the organ meets an organ-specific value which is equivalent to its sink strength.
In other words, the sink strength of an organ depends on the amount of nitrogen it receives.
Stems and leaves have a higher capacity to accept nitrogen distribution than fruits.
Therefore, when an excess amount of nitrogen is absorbed, it is distributed to the leaves and stems, increasing sink strength.
This results in more C being distributed to the stem and leaves, explaining the phenomenon of larger leaves and inferior fruit enlargement.
The implementation of this model helps to optimize nitrogen supply and temperature management in the greenhouse and contributes to stabilizing flower bud differentiation, increasing flower number and promoting fruit enlargement.

International Symposium on New Technologies for Sustainable Greenhouse Systems: GreenSys2023

Y. Iwasaki

sink, source, dry matter distribution, nitrogen distribution, flower bud differentiation, fruit enlargement

https://doi.org/10.17660/ActaHortic.2025.1426.12