SOME RESULTS ON WATER AND NUTRIENT CONSUMPTION OF A GREENHOUSE TOMATO CROP GROWN IN ROCKWOOL

Transpiration (TR) and nutrient consumption (N) of a greenhouse tomato crop grown in rockwool were monitored during spring and summer periods.
Transpiration measurements were obtained by two ways:

1. hourly values given by an electronic balance supporting four plants;

2. daily values estimated by the difference between supply and drainage rates of a complete row (108 plants).

Nutrient (NO3, K, Ca, Mg and P) concentration in the solutions (supply and drainage) were determined each week from chemical analysis of samples of both solutions.

Data on crop transpiration obtained with the two methods agree fairly well at daily scale.
They were used to test and validate two models of canopy transpiration (TR):

1. a model based on the Penman-Monteith approach, where stomatal resistance to water vapour transfer is expressed as a function of global radiation (G) and vapour pressure deficit (D);

2. a simplified formula derived from the previous model: TR = A^*G + B^*D, where A and B are two parameters that were identified by fitting the calculated and measured transpiration all along the crop development (April to July).

Comparison between predicted and measured values showed that the two models simulate quite closely crop transpiration.

The data on mineral absorption of the system (crop + substrate) indicated that the absorption rates of the various nutrients (N) followed quite closely the transpiration rate.
The ratio N/TR remained rather stable for all components, with some slight fluctuations for NO3 and K.

International Seminar on Soilless Culture Technology Protected Crops Mild Winter Climates

R. JEMAA, T. BOULARD, A. BAILLE

greenhouse, irrigation, model, nutrient uptake, transpiration, tomato

https://doi.org/10.17660/ActaHortic.1995.408.14