Fig. 2 shows a cross-section of one row unit of a tractor-mounted seed planter. (a) Name the parts labelled X, Y and Z on the diagram. [3] (b) Describe how ...

Labelled answer diagram:

(a) The labelled parts of the tractor-mounted seed planter are:

• X - Seed hopper (seed box) [1]. This is the container that holds the seed supply. It is filled before planting begins and feeds seed to the metering mechanism by gravity.
• Y - Metering mechanism (seed plate) [1]. This device controls the rate at which seeds are released from the hopper, ensuring a consistent number of seeds are dropped per unit length of row.
• Z - Furrow opener (coulter) [1]. This is a pointed or disc-shaped component that cuts a narrow groove (furrow) in the soil ahead of the seed drop point.

(b) How the seed planter places seeds into the soil:

1. The furrow opener cuts a narrow groove in the soil as the planter moves forward [1].
2. The metering mechanism releases seeds at a controlled rate from the hopper into the furrow at the correct spacing [1].
3. A press wheel or covering device behind the seed drop closes the furrow and firms the soil over the seeds, ensuring good seed-to-soil contact for germination [1].

(c) Why calibration of the seed planter is important:

1. Calibration ensures the correct number of seeds is dropped per unit area or per metre of row [1].
2. If too many seeds are dropped, it wastes expensive seed and causes overcrowding. Overcrowded plants compete with each other for light, water, and nutrients, reducing individual plant yield [1].
3. If too few seeds are dropped, the result is a poor plant stand with gaps in the rows, which reduces total yield per hectare and allows weeds to establish in the gaps [1].

(d) Three maintenance practices at the end of the planting season (any three) [3]:

1. Clean all soil and plant debris from the planter to prevent corrosion and blockages [1].
2. Apply grease or oil to all moving parts (metering mechanism, bearings, chains) to prevent rust during storage [1].
3. Store the planter under cover in a dry shed to protect it from rain and weathering [1].

Other valid practices: check and replace any worn or damaged parts such as the furrow opener or seed plates; release tension on belts and springs to prolong their life during storage.