Plant Protection Equipment Questions and Answers

Answer: A

The swath narrows by 0.23 m.

Each nozzle sprays a cone of included angle 75 degrees, so its swath width at height h is \(2h\tan 37.5^{\circ}\). The boom's overall swath is the nozzle spacing times the gaps between nozzles plus the spread of the end nozzles, and only that spread depends on the height:

\[ \begin{aligned} \Delta W &= 2\,\Delta h\, \tan 37.5^{\circ} \\ &= 2 \times (0.75 - 0.60) \times 0.767 \\ &= 0.23\ \text{m} \end{aligned} \]

Counting the change once per nozzle instead of once for the boom multiplies it by 12, which is not offered, and using tan 75 degrees in place of the half-angle gives 1.12 m. 0.48, 0.65 and 0.91 are not produced by this geometry.

Answer: A

Higher spraying pressure results in a reduction of droplet size.

A hydraulic nozzle breaks the liquid into a sheet that disintegrates into droplets. Higher pressure gives a faster, thinner sheet that breaks up into finer droplets, and also increases the flow rate. That is why drift increases at high pressure: small droplets are carried by wind.

Droplets get larger, not smaller, when pressure is lowered, so 'Increase of droplet size' is the reverse. 'No change' is wrong because pressure is one of the main controls on droplet size, along with nozzle type and orifice size.

Answer: C

An air blast sprayer is used for orchards.

In an air blast (air carrier) sprayer, the liquid is broken into droplets by nozzles or by the air stream, and a large fan blows a high-volume air blast that carries the droplets into the canopy of tall trees. The air displaces the air inside the canopy and shakes the leaves, so both sides of the foliage are covered, which is what fruit trees need.

Field crops are low and are sprayed with boom sprayers. Gardens and nurseries are small areas suited to knapsack or hand sprayers. The air blast is needed only for tall, dense canopies such as orchards.

Answer: D

The knapsack sprayer suits all three, so the answer is All are correct.

A knapsack sprayer is carried on the operator's back and is either hand-operated (lever) or engine-powered. Its lance can be pointed at low or high targets, so it is used on bushes ('brushes' as printed), on row crops, and on small trees in nurseries and young orchards. It is the most common sprayer on small Indian farms.

Choosing only one of bushes, row crops or small trees understates the sprayer's range; it is a general-purpose sprayer for small areas.