CONTROL OF NUTRIENT SOLUTION CONCENTRATION DEPENDING ON GREENHOUSE CLIMATE IN A SWEET PEPPER CROP

Water and nutrients are taken up by plants influenced by environmental conditions.
In this study models of photosynthesis and transpiration were used to calculate the ratio of nutrient uptake to water uptake for a sweet pepper crop.
From these models an algorithm was derived to control the concentration of nutrient solution depending on global radiation.

The algorithm was tested in a sweet pepper crop grown on rockwool from March to November and compared to a constant nutrient concentration (commercial standard). The concentration of nutrient solution in the model treatment was adjusted each morning depending on global radiation expected for the day.

The set point for the nutrient solution concentration of the model treatment was lower than for the standard when solar radiation increased.
On average over the growing period electrical conductivity of nutrient solution in the root environment was 2.8 dS m^-1 for the model treatment and 3.0 dS m^-1 for the standard.
This resulted in a 13 % higher marketable yield of the model treatment mainly due to a decrease of the fraction of fruits with blossom end rot.

International Symposium on Water Quality & Quantity-Greenhouse

H.-P. Kläring, W. Cierpinski

Capsicum annuum L., Electrical conductivity, Model, Photosynthesis, Transpiration

https://doi.org/10.17660/ActaHortic.1998.458.15