3 Fig. 3.1 shows the construction of a fence used to enclose a grazing pasture. (a) Name the type of fence shown in Fig. 3.1. [1] (b) State three factors a ...

Labelled answer diagram:

(a) The type of fence shown is a post and rail fence. [1]

(b) Three factors to consider when choosing a fence type:

1. Cost of materials: the farmer must balance the upfront expense against the farm budget and the length of fencing required. [1]
2. Type of livestock to be enclosed: different animals require different fence heights, wire spacings and strengths (e.g. cattle vs. poultry vs. goats). [1]
3. Durability and expected lifespan: a more durable fence (e.g. stone wall) costs more initially but may be cheaper over decades than a fence needing frequent replacement. [1]

Other acceptable factors: purpose of the fence; availability of local materials; ease of construction; terrain of the land; length of fencing needed.

(c) A strainer post provides strong anchorage at corners and at the ends of a fence line to maintain wire tension along the entire run. [1] Without strainer posts, the wire would gradually slacken as intermediate posts are not braced to resist the pulling force of taut wire.

(d) Why wooden posts are treated with preservative:

1. The buried section of the post is in constant contact with damp soil, making it highly susceptible to rotting caused by fungal decay. [1]
2. Preservative treatment (e.g. creosote or CCA) extends the working life of the post by preventing decay and protecting against termite and insect attack. [1]

(e) Two differences between permanent and temporary fences:

1. Permanent fences are fixed in position and built from strong, durable materials (treated wooden posts, wire, concrete), while temporary fences (e.g. portable electric fencing with lightweight metal stakes) can be moved from one location to another. [1]
2. Permanent fences are more expensive to build and are designed to last many years, while temporary fences cost less and are intended for short-term use such as rotational grazing or protecting a single season's crop. [1]

(f) Two reasons why proper wire tensioning is important:

1. Loose, sagging wire allows animals to push through or step over the fence, defeating its purpose as a barrier. [1]
2. Properly tensioned wire distributes stress evenly along the fence line, reducing the chance of breakage from wind, animal pressure or temperature changes. [1]

Other acceptable: good tension prevents posts from leaning; maintains correct spacing between strands.

(g) Fencing is important on a mixed farm to separate livestock from crop fields so that animals do not enter and damage or eat the growing crops. [1]