Land Preparation and Crop Establishment
What you must understand
Know the purposes of land preparation: clearing, loosening, levelling, incorporating residues, controlling weeds and creating a seedbed. Distinguish primary tillage (ploughing, ripping, subsoiling) from secondary tillage (harrowing, discing, levelling, rolling). Understand conservation tillage and zero tillage, which reduce erosion and conserve moisture but may need more herbicide and can build compaction.
Know seed quality (viability, vigour, purity, germination percentage), seed rate, plant population, spacing, planting depth (generally 3–6 cm, deeper in dry sand, shallower in clay), and row spacing. Understand sowing methods (broadcasting, drilling, dibbling, transplanting) and their advantages. Know the seedbed requirements: fine tilth, adequate moisture, good aeration, free of weeds. Understand nursery practice for transplanted crops such as tobacco, rice and vegetables. Know how to calculate germination percentage and pure live seed.
Traps in questions
- Ploughing is primary tillage; harrowing is secondary.
- Deep planting in heavy clay causes poor emergence, not better moisture uptake.
- Plant population is plants per unit area, not seed mass sown.
- Broadcasting uses more seed than drilling and gives uneven stands.
- Zero tillage is not "no management"; it needs residue cover and weed control.
Rule of thumb
Aim for a fine, firm, moist seedbed: fine enough for seed-soil contact, firm enough for capillary rise, moist enough for germination, and free of weeds.
Worked example
Seed has 85% germination and 95% purity, so pure live seed = 0.85 × 0.95 = 0.81 (81%). To establish 100 000 plants/ha, sow 100 000 ÷ 0.81 ≈ 123 500 seeds/ha. At 1 000-seed weight of 300 g, that is about 37 kg/ha.