On-line Monitoring of Protected Crops and their Environment: Towards the Speaking Plant.

Keywords: Transpiration, Crop models, Sensors, Lysimeter.

Abstract
The horticultural industry is rapidly changing from a producer to a consumer orientated industry. Changes include the need for more planned and sustainable production, which requires less input of fertilizers, energy and crop protecting agents. Setpoints for greenhouse controllers are at best obtained from experience, trial and error, or experiments. On-line interpretation and use of signals from plants and their environment (the 'speaking plant' approach), could directly or indirectly give feedback to controllers as a warning system for stressful conditions. Examples of monitoring in relation to both unwanted and beneficial stress conditions are given. Sensor requirements, spatial variability, data interpretation and the possible uses of sensors in control systems are considered.

The practical questions a grower faces with plant-monitoring equipment are addressed. For improving plant quality and yield prediction, a combination of plant monitoring and empirical or mechanistic crop growth and development models is promising. Examples are the graphical tracking and visual quality of pot plants, and yield prediction of tomato.

Rob Baas, Applied Plant Research, Business Unit Glasshouse Horticulture, Linnaeuslaan 2a, 1431 JV Aalsmeer, the Netherlands.

20 Pages, 8 Figures, 2 Tables, 24 References.


Water Stress and Root Disease Detection in Protected Crops by Routine Measurements.

Keywords: Greenhouse, Stress, Environment monitoring, Hydroponics.

Abstract
Early detection of crop stress is especially beneficial in greenhouses, because the highly controllable environment makes it possible to take corrective actions once the onset of stress has been detected. While information about the well-being of a given plant can be obtained by direct measurements (e.g. leaf position, sap flow, transpiration rate), this 'speaking plant' approach has the disadvantage that the small number of plants that can be monitored are not necessarily representative of the whole greenhouse.

This paper presents a different approach. It is based on monitoring the crop environment and uses changes in the environment as indicators of stress and is illustrated using two case studies, in which the root and shoot environment, respectively, are monitored.

Raphael Linker and Ido Seginer, Faculty of Civil and Environmental Engineering, Lowdermilk Division of Agricultural Engineering, Technion-Israel Institute of Technology, Haifa 32000, Israel.
Leslie S. Katzman, Department of Floriculture and Ornamental Horticulture, Cornell University, Ithaca, NY, USA.

13 Pages, 6 Figures, 1 Table, 13 References.


Monitoring of Nutrients and Water in Closed (Recycled) Systems for Ornamentals.

Keywords: Recycled irrigation and fertigation system, Long-term monitoring, water use efficiency in a closed system, ornamentals.

Abstract:
Long term monitoring of irrigation and fertigation management, overall estimation of the water requirement of potted ornamentals and water use efficiency evaluation in a recycled system was conducted over a period of 18 months. The water source for irrigation was either desalinised water or rain water. The overall annual crop water requirement was found to be, on average, 2 mm/day, and the water use efficiency of the recycled system was 95%. Long term chemical monitoring of the recycled solution showed that in a system where chloride levels are very low, electrical conductivity, rather than chloride concentrations, can be used as a parameter for dilution and disposal of the solution from the system, according to the pre-determined threshold level. High sensitivity to pH fluctuations was observed due to the low bicarbonate levels as a result of using desalinised water and/or rainwater. An additional iron supplement was found to be necessary.

A Lowengart-Aycicegi, M Eisinger, Extension Service, Ministry of Agriculture and Rural Development, Western Galilee District, 25212 Oshrat Mobile Post, Israel.
A Avidan, Subject Matter Specialist for Protected Agriculture, Extension Service, Field Service, Ministry of Agriculture and Rural Development, P.O.Box 28, Beit Dagan 50250, Israel.
Y Shefer, A Shefer, B Shefer and V Shefer, 'Shefer Nurseries', Michael St., #50, Kfar Bialik 27905, Israel.

10 Pages, 7 Figures, 1 Table.