Protected Cultivation Questions and Answers

Answer: C

Strawberry is the fruit crop suited to plastic walk-in tunnels. It is a low-growing, short-duration, high-value crop whose fruit needs protection from rain and frost and benefits from a controlled, warmer growing space, so it is routinely grown under plastic tunnels for off-season and quality fruit.

Apple, jackfruit and mango are tall perennial trees that cannot be grown under a walk-in tunnel, so they are not the answer.

Plastic walk-in tunnels are large enough for a person to walk inside and are used for high-value, short, low-growing crops. Strawberry fits this use, and it is often grown on raised beds under tunnels to keep the berries clean and dry.

Answer: B

The key gives maintaining the carbon dioxide concentration. Low tunnels are small plastic covers over a crop row, and one source I found says they trap CO2 within the covered space and so help photosynthesis. Another measurement-based source found that CO2 in a closed tunnel falls during the day, so this is not a firmly established effect; I could not find a source that settles it.

Protecting from insects, holding humidity and the oxygen concentration are not the main principle given by the key, and oxygen is not a limiting factor for plants in the way carbon dioxide can be.

Answer: A

The key gives the 2-stem system. In a polyhouse the tomato is trained to one or two main stems, and the key picks two stems. I could not find a source comparing the one-stem and two-stem systems, so the choice rests on the key.

Growing without any system leaves the plant sprawling, and a 5-stem system gives too dense a canopy for a polyhouse crop.

Tomato in a polyhouse is an indeterminate type that is trained up a string, and the number of stems left on a plant sets the plant density and yield. Pruning to two stems is a common choice and is the one the key gives.

Answer: B

In a glasshouse, strawberry is propagated by runners. The mother plant sends out runners, long stems that root at the nodes and form new plantlets, which are separated and planted.

Stem cuttings, layering and crowns are not the usual multiplication method in a glasshouse, although crown division is possible.

Strawberry plants send out stolons, called runners, which form daughter plants at the nodes. These daughter plants are rooted and used as planting material, which is the standard multiplication method.

Answer: A

The key gives 200-250 flowers per square metre per year. I could not find a source confirming the figure; gerbera yields under a greenhouse are commonly quoted as a few hundred flowers per square metre a year, and the options differ widely, so this is kept on the key.

The ranges 350-400, 450-550 and 600-700 are higher than the key's figure.

Greenhouse yield of gerbera varies with the cultivar and the management, and the values vary widely across the options. The key's figure is the lowest of the four ranges.

Answer: B

Off-season cucurbit seedlings in a polyhouse are raised in December and January. The structure protects the seedlings from cold, so that the crop can be planted early and harvested before the main season.

June to July, May to June and August to September are the normal seasons for cucurbits, not off-season.

Seedlings of cucurbits raised in winter inside a polyhouse are protected from frost and cold, so the plants are ready for planting early in spring and the crop reaches the market before the main season, when prices are better.

Answer: C

French marigold is not commercially suited to polyhouse production: it is a hardy annual that grows well in the open field at low cost, so a polyhouse is not worth the expense. Cut rose, gerbera and carnation are high-value cut flowers for which controlled conditions pay.

French marigold is a low-cost bedding and cut-flower crop that grows well in the open, so the extra cost of a polyhouse is not recovered. Roses, gerbera and carnation need steady temperature and protection from rain to give quality stems.

Answer: A

Long melon, a cucurbit, is suited to low tunnels. Low tunnels protect the young plants from cold early in the season and allow early planting.

Tomato, capsicum and chilli are taller and need other protection, such as trellises or polyhouses.

Low tunnels are used for crops that need only a few weeks of protection early in the season, such as cucurbits. Tall crops such as tomato, capsicum and chilli outgrow a low tunnel.

Answer: B

The key gives 9 to 10 months for the time a tomato crop can grow under greenhouse conditions with indeterminate hybrids. I could not find a source with the figure, so this rests on the key.

4-6 months is the length of an ordinary field crop, and the longer ranges are beyond what the crop is kept for.

Indeterminate tomato hybrids in a greenhouse continue to grow and bear for many months with training. The key gives the period as 9 to 10 months.

Answer: A

Glazing material in polyhouse construction refers to the covering material: the transparent or translucent sheet, such as polyethylene film, polycarbonate or glass, that covers the frame and lets light in while holding the heat.

It is not the growing medium, irrigation material or the matting used on the floor.

The glazing keeps out rain, lets in light and holds the warmth. Ultraviolet stabilised polyethylene film is the most common glazing in India, because it costs less than glass or polycarbonate.