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NCSU HS 301 - Lab 1 Review Questions

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Lab 1 Review QuestionsJenna Barnes1. What is the function of the solenoid valve in an intermittent mist system? Explain how the solenoid valve (normally closed version) in the class mist beds operates.- The solenoid valve controls water flow through the mist system by getting an electrical signal to open intermittently from a control box.2. All media brought into the Horticultural Science greenhouses are steam sterilized (actually pasteurized) before use. Distinguish between sterilization and pasteurization. What temperature is used and for how long is this temperature maintained during soil pasteurization? What is the advantage of pasteurization as compared to sterilization?- Sterilization will kill all microbial life in the soil whereas pasteurization only kills pathogenic microbes. There are beneficial microbes in media that we want to keep for the plants which is why pasteurization is better than sterilization in this situation.The media is steamed at 160 degrees Fahrenheit for 30 minutes.3. What components are mixed together to create the propagation mediawe use in our flats in this class? What is the ratio of the mixture of these components?- A 1:1 ratio of peat and perlite is used for the media we use in class. 4. Explain how a Mist-A-Matic ("mechanical leaf") functions to regulate mist application. What is the advantage of a mechanical leaf for mist regulation as compared to a timed-based controller?- The mechanical leaf system operates based on the condensation on the leaf screen and the system is activated when the leaf is close to dry and mimics the leaf surface that needs moisture. This system is beneficial because it is irrigating in response to the actual environment of the plants instead of on a timer system.5. In place of a Mist-A-Matic, the automatic timing of mist application on a 24-hour cycle could be regulated by 2 time clocks. What 2 types of clocks would you need, and briefly explain how these time clocks would function.- You have to have a 24 hour clock as well as an interval timer. The 24 hour clock allows you to set the time of day you want the system to operate (ex. 6am-6pm) and the interval clock allows you to set how often the system comes on (ex. Every 6minutes).6. A mechanically operated gate valve is usually integrated into a water line that bypasses the solenoid valve in a mist propagation system. Why would this be a good idea?- In case of a power outage, you can manually operate the valve to ensure the plants don’t die from a lack of irrigation.7. Distinguish between ‘duration’ and ‘frequency’ in an intermittent mist system.- Duration is how long the plants are misted when the system comes on and frequency is how often the mist is applied to the plants.8. What are 2 advantages to the use of an electronic controller for controlling mist operation as compared to a cycle timer if you have a greenhouse with multiple mist beds?- You can set the duration of misting whereas cycle timers have a factory setduration. You can also use different mist regiments for different benches if the plants call for it. 9. What is the typical voltage of the solenoid valve used in a mist propagation system? Why is this voltage used?- The typical voltage is 12 volts and this is used because a system that is near waterand electricity needs to have a low voltage for safety

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