Digital Commons Network^™

Continuous Ph Monitoring And Control: Selecting And Interfacing The Electrode, Controller, And Datalogger, Noah J. Langenfeld, Bruce Bugbee

Techniques and Instruments

pH control is essential to well-managed hydroponics. Here, we describe the selection and interfacing of electrodes, controllers, and loggers.

Far-Red Photography For Measuring Plant Growth: A Novel Approach, Cole Webb, F. Mitchell Westmoreland, Bruce Bugbee, Xiaojun Qi

Techniques and Instruments

A critical part of agricultural studies is determining plant stress and growth rate. Modern computer vision provides a series of tools that can be applied to derive this data. In this paper, we will show our findings, analyze their accuracy, and define a system capable of deriving this data with near-human accuracy in a fraction of the time. Denoising techniques applicable to this system will be discussed, as will our discoveries and findings. Finally, suggestions for further research opportunities will be provided.

Evaluation Of Five Conductivity Meters, Saundralyn G. Rhoades, Bruce Bugbee

Techniques and Instruments

Prices of conductivity meters vary widely. Here we report the response time, stability, and linearity of five meters.

Conclusions
The Hanna HI 98188 and the YSI Pro 30 are the two most expensive meters and they were the most stable. They were within 5% of the actual conductivity.

The Blue Pen was consistently closer to the actual conductivity than the other two Hanna meters and at only $20 it is a cost effective meter.

A Comparison Of Methods For Measuring Co2 And O2, Jake Nelson

Techniques and Instruments

Understanding the dynamics of respiratory gasses gives critical insight into the metabolic processes of a biological system. An efficient and effective means of measuring respiration is essential to understanding aspects of the biosphere. Many methods have been developed for measuring changes in CO₂ and O₂, both as integrated systems and as individual components. Many experiments use an alkali trap with subsequent titration as an inexpensive method for CO₂ measurement. Haney et al. (2008) compared the titration method against infrared gas analysis (IRGA) and found them to be highly correlated, with r²=0.95. The use of …

Carbon Use Efficiency: Adaptation To Changing Environments, Jonathan Frantz, Bruce Bugbee

Techniques and Instruments

Most shade adaptation occurred within two days during vegetative phase.

Up to 12 days were required for complete adaptation.

Different species adapted differently.

Helium Quality Affects Thermal Desorber Calibration, Joseph F. Romagnano, Bruce Bugbee

Techniques and Instruments

Thermal desorption technology increases the sensitivity of gas chromatography, but it also can concentrate contaminants from any gas stream that passes over a trap.

If contaminants interfere with the elution of the compound of interest, it is impossible to get a clean blank run (no sample applied yet there is still a peak) and the calibration curve will not pass through zero. This may be the result of contamination in either the gases used to blend the standards (trap tubes) or gases used internally by desorber (cold trap). However, when combined with an inability to get a clean zero, the …

Downward Blue Drift Of Quantum Sensors, Alec Hay, Bruce Bugbee

Techniques and Instruments

Silicon photodiodes are known to decrease more rapidly in response to blue light than to longer wavelengths (Korde and Geist, 1987). Older quantum sensors thus appear to calibrate accurately using the LI-COR 1800-02 Optical Radiation Calibrator, but may under-report radiation in the 400 – 500 nm wavelengths (blue) due to degradation of the silicon photodiode in the sensor.

Greenhouse Studies On Root Growth And Morphology, Julie K. Chard

Techniques and Instruments

For studies of root growth and morphology, an ideal containerized plant culture system should provide: 1) adequate nutrients, water and oxygen; 2) appropriate mechanical impedance to root elongation; 3) adequate depth to prevent root binding; and 4) easy separation of roots from the root-zone substrate.

Columnar containers are preferable to pots because they can support deep root growth while taking up less bench space. Many columns can be arranged within a small area, such as a gas-exchange chamber, thereby maximizing the number of treatments and replications in a given space.

Standard potting substrates typically contain sphagnum peat mixed with perlite …

Emerging Research Techniques & New Instrumentation For Plant Biology, Bruce Bugbee

Techniques and Instruments

We have not achieved an efficient food production system in US Agriculture by manipulating only the environment.

Genetic engineering techniques now allow us to quickly develop new crop cultivars.

Changing The Integration Time Has A Minimal Effect On The Accuracy Of The Apogee / Stellarnet Spectroradiometer, Nick Knighton, Bruce Bugbee

Techniques and Instruments

Changing the integration time has the potential to change the accuracy of the Apogee/StellarNet spectroradiometer. All Apogee/StellarNet spectroradiometers are calibrated to an NIST traceable calibration lamp. This lamp (LI-COR Inc., model 1800-02; Lincoln, NE) has an output of 206.2 µmol m^-2 s^-1, which requires a relatively long integration time (about 500 ms) to obtain a full scale response. Sunlight and high-wattage electric light sources often have a much higher intensity, which require much shorter integration times (10 to100 ms) to prevent light saturation of the detectors. The accuracy might be affected differently by increasing or decreasing integration …

A Mixture Of Barium Sulfate And White Paint Is A Low-Cost Substitute Reflectance Standard For Spectralon®, Nick Knighton, Bruce Bugbee

Techniques and Instruments

Barium sulfate is a white powder that has historically been used as a reference standard (Weidner and Hsia, 1981). It may be a less expensive alternative to higher priced white standards that use sintered PTFE (polytetrafluoroethylene; Spectralon®, Labsphere, Inc., North Sutton, NH). A 500 g bottle of BaSO4 costs $25, whereas reflectance standard made of Spectralon® and with a 99% reflectance factor costs $385. However, pure barium sulfate dries to a powder and easily rubs off surfaces. We sought to increase the durability of barium sulfate by mixing it with untinted white latex paint. Reflectance and durability of different ratios …

Spectrometer Curve Smoothing Using Replicate Scans And Running Averages, Nick Knighton, Bruce Bugbee

Techniques and Instruments

The Boxcar Pixel Smoothing algorithm significantly reduced noise in spectral traces. However, averaging replicate scans did not significantly reduce noise in these studies.

Simulating The Field: How To Grow Plants In Soil Columns In The Greenhouse, Julie K. Chard, Bruce Bugbee

Techniques and Instruments

Why Soil Columns?

In the field of plant research it is often desirable to grow plants under controlled conditions to minimize environmental variability from one treatment to the next. The desired control can be achieved by growing plants in containers in a greenhouse or growth chamber.

Plant growth in soil is straightforward in the field where soils are deep, but soil moisture dynamics are altered significantly in small containers. Drainage in the field results from the depth (thickness) of the soil layer. Gravity alone is not adequate to remove water from agricultural soils in pots.

Soil columns are an improvement …

Comparison Of The Analytical Spectral Devices Fieldspec Pro Jr And The Apogee/Stellarnet Model Spec-Par/Nir Spectroradiometers, Daniel Dallon

Techniques and Instruments

Spectroradiometers can be used to identify plant stress by measuring crop reflectance. Spectroradiometers can measure nitrogen and water stress, and subsequent adjustments in applications can improve crop yield and reduce over-application. Two portable spectroradiometers and their accompanying software were compared for accuracy and ease of use while conducting experiments to determine water and nitrogen stress in crested wheat grass and soybean plants. The first unit was a higher priced ($40,000) visible/NIR triple diodespectroradiometer (ASD FieldSpec Pro JR) with a range of 350-2500 nm. It uses ASD’sFieldSpec Pro RS3 software. The second was a low-priced ($3600) visible/NIR fixed diode spectroradiometer (Apogee/StellarNet …

A Simple Test To Evaluate The Calibration Stability And Accuracy Of Infrared Thermocouple Sensors, Derek R. Pinnock, Bruce Bugbee

Techniques and Instruments

Accurately measuring surface temperature is not difficult when the surface, the sensor, and air temperatures are similar, but it is challenging when the surface temperature is significantly different than air and sensor temperatures.

We tested three Infrared Thermocouple sensors (IRT’s) that had been used for two years in a greenhouse environment. The importance of the correction for sensor body temperature was also examined.

Non-Destructive Determination Of Leaf Expansion Using A Digital Camera, D. R. Pinnock, S. P. Klassen, Bruce Bugbee

Techniques and Instruments

Leaf expansion is reduced in mild water stress. Early detection of water stress can be accomplished with digital images taken at daily or hourly intervals.

Conclusions

• Digital cameras can be used to determine leaf expansion and relative growth rate.
• Digital cameras can also be used to detect early symptoms of water stress.

Determining The Environmental Factors Controlling Respiration: Interpreting The Temperature Response, Jonathan Frantz, Marc Van Iersel, Bruce Bugbee

Techniques and Instruments

• Concept of Q₁₀is too simplified.
• Specific temperature sensitivities are often ascribed to species rather than method.
• Too much emphasis is placed on temperature in determining respiration rates.