Agricultural and Biosystems Engineers Licensure Examination Protected Cultivation & Greenhouse Engineering: practice questions

Question 1 · easy

A grower plans a greenhouse with soilless culture and fan-pad cooling. Which site check is most often the deciding one?

1. Texture of the field soil, since roots in substrate still draw water from it
2. Quality of the irrigation water, including sodium, bicarbonate, boron and iron
3. Distance to the nearest forest, since trees supply carbon dioxide to the house
4. Colour of the local soil, since dark soil raises the light inside the house

Question 2 · easy

On a calm, clear winter night, a crop under a single layer of plain polyethylene can be colder than the outside air. Why?

1. The film reflects the heat from the soil downward and freezes the crop by conduction
2. The film absorbs moisture from the air, which takes heat from the crop as it freezes
3. The film conducts heat from the crop to the steel frame, which then acts as a large cooling fin for the whole crop
4. The film passes the crop's long-wave radiation to the cold sky while blocking warm air from the crop

Question 3 · medium

Natural ventilation through a 6,000 m³ greenhouse is 45 m³/s. How many air changes per hour is this?

1. 27 per hour
2. 0.45 per hour
3. 133 per hour
4. 2.2 per hour

Question 4 · medium

Why is a continuous bleed-off of water from the sump of a pad-cooling system recommended?

1. To limit the build-up of dissolved salts, which otherwise crust on the pad and block it
2. To keep the pump from running dry, because pads absorb all the water that is supplied
3. To cool the sump water below the outside wet-bulb temperature, so the pad works better than its rating
4. To remove dissolved oxygen, which otherwise rots the cellulose fibres of the pad

Question 5 · medium

Compared with fan-pad cooling, what is the main advantage of a high-pressure fog system?

1. It cools the air throughout the house and works with natural ventilation as well as fans
2. It cools air below the wet-bulb temperature, which no fan-pad system is able to do
3. It works with untreated, hard water, because fine nozzles cannot be blocked by salts
4. It lowers the humidity inside the house at the same time as it cools, so disease pressure falls sharply

Question 6 · medium

Outside illuminance is 90 klux. The greenhouse cover transmits 80% and an external net rated at 40% shade is drawn. Roughly how much light reaches the crop?

1. 28.8 klux
2. 43.2 klux
3. 36.0 klux
4. 54.0 klux

Question 7 · easy

Why do growers stop enriching CO₂ above the outdoor level once the vents open wide for cooling?

1. The crop stops photosynthesising when vents open, so it no longer takes up any CO₂
2. The added CO₂ escapes with the ventilation air almost at once, so enrichment becomes uneconomic
3. Open vents let oxygen in, which reacts with the added CO₂ and destroys it before the crop takes up any of it
4. The CO₂ sensors stop working in moving air, so dosing cannot be controlled at all

Question 8 · easy

Tall vine crops such as greenhouse tomato and cucumber are most commonly grown soilless in

1. floating rafts on deep water, with plants held in foam plugs
2. aeroponic towers, with the roots misted inside closed columns
3. rockwool or coir slabs or bags, fed by drippers
4. nutrient film channels, with the roots in a thin flowing film

Question 9 · hard

Which statement about liners for farm ponds is correct?

1. LDPE film can be left exposed to sun for decades, while HDPE geomembrane must always be buried under soil
2. LDPE film must be covered with soil or masonry, while carbon-black HDPE geomembrane can be left exposed
3. Both LDPE and HDPE resist ultraviolet light fully, so neither needs any protective cover
4. Neither material reduces seepage, so they are used only to keep pond water free of algae

Question 10 · medium

Before laying a plastic liner in a new farm pond, which preparation is standard practice?

1. Fill the pond with water first, so that the liner floats gently into place on the water surface and settles
2. Spread coarse gravel on the bed, so the liner drains freely from below once filled
3. Compact the subgrade, remove stones and roots, and dig an anchor trench around the top edge
4. Burn the vegetation on the bed, so the ash forms a seal under the liner