Crop Science and Crop Production Systems
Core concepts
Understand crop classification (cereals, legumes, oilseeds, root and tuber, fiber, forage), growth stages and phenology (vegetative, reproductive, maturity), and the drivers of yield: intercepted radiation, water, nutrients, and harvest index. Know the difference between C3, C4, and CAM photosynthetic pathways and their environmental adaptations. Master cropping systems terminology-monoculture, multiple cropping, intercropping, relay cropping, crop rotation, and agroforestry-and the agronomic benefits of rotation such as breaking pest cycles and nitrogen fixation by legumes. Understand planting density, plant population calculations, seed rate, and the concept of the critical period for weed competition.
Traps in questions
Do not confuse intercropping (two crops simultaneously in the same field) with relay cropping (overlapping but staggered planting) or sequential cropping (one after another). Remember that C4 crops (maize, sorghum, sugarcane) are more water- and heat-efficient but not universally higher-yielding under cool conditions. Watch for questions treating plant population as independent of row spacing and seed germination percentage.
Worked example
Target population 60,000 plants/ha with 75 cm rows and 95% field germination. Plants per meter of row = 60,000 / (10,000 / 0.75) = 60,000 / 13,333 ≈ 4.5 plants/m. Adjusting for germination: seed 4.5 / 0.95 ≈ 4.7 seeds/m. Rule of thumb: convert target population to plants per meter of row using the row-width factor before adjusting for germination.
Rule of thumb
Always express population per unit area, then convert to per-row-length using the spacing, and only then correct for germination and emergence.