Installation of Greenhouse Crop Monitoring System

• To evaluate sensor application, information on measurements associated with crop response to changes in substrate moisture, weight and variations within the plant growth in greenhouse vegetable crops.
• To operate and evaluate whether these sensors are suitable for the greenhouse use and to provide data that will assist the irrigation and environmental management of the crops based on the data from these sensors.

• Upper load cell.
• Lower load cell.
• CS655 (water content reflectometer probe).
• Apogee IRR-P (Infrared temperature sensor).
• PAR (Photosynthetically Active Radiation).

• A datalogger CR3000 (Campbell Scientific Canada Corp, Edmonton, AB) provided all data collection functions from the sensors. The datalogger communicated with the PC via a communication cable (Figure 2).
• The multiplexer AM16/32B provides a connection of the load cells (to the datalogger for measurement and data acquisition /processing).
• The NL115 to connect the datalogger to an Ethernet network and transfer data to the base station for remote monitoring.
• The ENC 16"x18" enclosure (white box) to house the CR3000 and the multiplexer.
• Power supplies for communication between the sensors, datalogger and computer room.
• Fiber-optic cable for faster transferring of the information to the computer room.
• Two trays containing the plants.
• Two stations of the soilless growing medium (coconut coir and biochar).

• Loggernet 3.4.1. (Figure 3) a Campbell Scientific program was used to collect data generated by the CR 3000 and transfer to a source file on the PC.

• The real time data from the upper, lower load cells, PAR, IRR and CR655 can be display automatically every 15 minutes, hourly, daily, weekly intervals throughout the growing season either graphically or in tables, and is also archived. The datalogger memory 2MB, can store several weeks of data from a single site.
• The datalogger was programmed to sample all instruments readings every 20 seconds and store the sample value of these results every 15 minutes and average every hour.
• The system will illustrate the measurements in tables for both stations (coco # 1) and (biochar #2) as the following in (Table 1) except the biochar station there is no CS655 sensor.

Sensor	Application	Measurement unit
Upper Load Cell	LC_Canopy1_Avg.	Kg
Lower Load Cell	LC_Media1_Avg.	Kg
PAR	Quantum 1_Avg.	ìmol m-2 s-1.
IRR-P	SBTempC_1_Avg (Sensor Body Temperature).	°C
	TBTempC_1_Avg (Target Body Temperature).	°C
CS655	VWC Avg (Volumetric Water Content).	m^3/m^3.
	EC Avg (Electrical Conductivity).	dS/m
	Tsoil Avg (Substrate Temperature).	°C

1. Upper load cell set-up An upper load cell set weighs the crop canopy for continuous measurements of daily growth (midnight to midnight).The plants were tied to a beam placed parallel to the crop wire but suspended from the load cells. The pair of the upper load cells are S–beam tension cells (AnyLoad Transducers, Model 101NSGS, BC, Canada), each load cell had a capacity of 50 kg. The upper load cells were suspended with metal chains to minimized lateral stress on the load cells which is a requirement for accurate readings. The measurements of the upper load cells included change in canopy weight (stems, fruits, flowers, leaves) mass.
2. Lower load cell set-up A set of lower load cells (weight scales) were used to monitor the plants growth weight gain (water contributing to growth).The substrate containing the plants is positioned on top of two single point load cells (AnyLoad Transducers, Model 108KSUN, BC, Canada), each with 50kg capacity The upper and lower load cells utilized the same plants. Load cell output was expressed in kilograms. The measurements of the lower load cells included: Weight of the crop growing medium.
3. CS655 water content Reflectometer set-up
   1. Coconut coir substrate:
      1. The probe CS655 (Campbell Scientific Canada Corp, Edmonton, AB) with the 12 cm rods was used for measuring the:
         1. Volumetric Water Content (expressed in m3 m–3), the probe provides information on the degree of saturation of the media.
         2. Electrical Conductivity (EC) expressed in dS/m (mS/cm).
         3. Temperature (°C).of the growth medium (soilless substrate).
   2. Biochar substrate
      1. Neither the CS655 probe nor a Hydra digital (Hoskin Scientific Limited, B.C Canada) gave substrate water readings for the biochar. It was presumed the inability of the probes to function in the biochar medium was due to elevated E.C values.
4. Apogee IRR-P (Infrared temperature sensor) set-up It measures the temperature at the top of the crop, which to a large extent determines the crop’s growth rate. The sensor was mounted at an appropriate distance from the target and is expressed in unit of degree Celsius (°C).They are useful tools as an indicator of plant stress.
5. Quantum sensor set-up It measures the number of photons in the photosynthetically active radiation (PAR) spectrum, which is light with a wavelength between 400 to700 nanometer; providing the energy for plant photosynthesis. The more PAR a plant receives, the more potential that plant has for growth. The unit of measurement is micromoles per square meter per second (ìmol m-2 s-1). Their placement at the top point in the plant canopy provides an immediate indication of whether the current light levels are sufficient or not.

• The first irrigation start 2 hours after dawn, from that time to the point of first drain there is increase in the substrate water content (VWC) and E.C (figure 8).
• Relationships shown here in the graph (figure 11) that the VWC will be stable and decreasing in the substrate E.C as the point of drain realised. This period normally transcends the point of highest solar radiation.
• From last irrigation in day 1 (2 hours before dusk) to first irrigation in day 2 there will be decreasing in the VWC and increasing in the EC.
• The measuring by CS655 probe showed increase in E.C with decreasing in the water content as the fertilizers in the pore water become more diluted as VWC increases.
• The water content of the plant increases by water uptake by the roots and decreases by transpiration.
• Daily fluctuations in water use will result in fluctuations in substrate volumetric water content, when plant water use is high, substrate water content will drop quickly.

• Both coconut coir and biochar stations (Table 2), the plants leaf temperature increased above the air temperature a few times because of the absorbed radiation.
• Leaf temperatures increased (2-3°C) during the afternoon because there was less cooling by transpired water as it evaporated from the leaf surfaces.
• Plant leaf temperatures will generally be warmer than air temperatures by day (around afternoon) but at night was slightly cooler (1-2°C) less than greenhouse air temperature.

• Plants need light (PAR), so increasing energy in the PAR range increases plant photosynthesis. The differences in PAR readings (Table 3) between the stations due to the location of the station, using the shade inside the greenhouse and the filtering of radiation by the greenhouse covering.
• Both photosynthesis and transpiration are dependent on solar radiation; more radiation means more CO2 uptake and also more transpiration.
• Along with daily (photosynthetically active radiation) and more radiation, water use tends to increase during the production cycle, as a result of increasing plant size.

Table 3 PAR readings & outdoor lights of coconut coir and biochar stations during July 15, 2013 in poly # 2.

1. Based on the decision of the greenhouse manager on that system, may be in the next growing season, September 2013,it is a good idea to try use the same system with Red-Hat trials on testing the plant growth of high wire cucumbers in poly # 2 and use different technique of upper load cells. Later on (January 2014) we will do another comparison of two seasons and years for peppers crop.
2. For crops such as tomato, we can use the other sensors but it is impractical to continuously use the same set of plants on the upper load cells for extended periods of time, because of lowering the plants on regular basis and by the end of the season the plant canopy may be over 10m from its roots. So it's better to choose different kind of load cells like weigh the whole plants on the trough instead of an individual plant.
3. In future experiments, we need to examine the relationship of the sensors we are currently using, and the effect of the environmental conditions (sunny and cloudy days) like solar radiation, relative humidity, CO2, greenhouse temperature, VPD and irrigation strategies (volume, start and stop time of watering) on the yield and crop performance in the greenhouse.
4. Extend the system by evaluating different technology like Priva top crop or Paskal growth analysis system.
5. Do the integration of GS 3 probe ((Decagon Devices, US) that with Argus software and view the information of the substrate water status in the Argus computer.