Crop Production and Plant Science
The Crop Production and Plant Science domain tests whether you can convert plant physiology and agronomy into field decisions: variety and rootstock choice, sowing and planting rates, timing of inputs, and diagnosis of yield gaps in Cyprus's irrigated and rainfed systems - potatoes, citrus, olives, vines, cereals and protected vegetables.
Physiology that changes management
- Photosynthetic pathway: C3 crops (wheat, potato, citrus, olive) lose carbon through photorespiration as temperature rises, so water-use efficiency falls in summer; C4 crops (maize, sorghum) and CAM crops (Opuntia) hold higher WUE where heat and limited water coincide.
- Vernalization and photoperiod: cereals and onions need low temperature and/or a specific daylength before flowering. Sowing date is a flowering-control tool, not just a calendar decision.
- Harvest index (HI) = marketable dry matter / total dry matter. Modern varieties raise yield more by raising HI than by raising total biomass, which is why late nitrogen and lodging cut HI without cutting biomass.
Thermal time
Growing degree days (GDD) = Σ [(Tmax + Tmin)/2 − Tbase], with temperatures capped at the crop's upper and lower limits. GDD predicts emergence, flowering and maturity better than calendar days and lets you stage pesticide timing and harvest.
Worked example - seed rate
Target 300 plants/m² of wheat; thousand-grain weight (TGW) 40 g; laboratory germination 95%; field establishment 90%. Seeds needed = 300 / (0.95 × 0.90) = 351 seeds/m². Seed weight = 351 × 40 / 1000 = 14.0 g/m² = 140 kg/ha. Reasoning: laboratory germination overstates field performance; establishment corrects for emergence losses. Note the direction - dividing by a fraction below 1 increases the rate.
Traps
- Multiplying by germination percentage instead of dividing: the seed rate comes out too low.
- Treating TGW as if it were the seed rate, or mixing grams and kilograms.
- Assuming a C4 advantage in cool spring conditions, where C3 crops often establish faster.
- Reading HI as yield; it is a ratio and says nothing about absolute biomass.
- Quoting a GDD sum without its base temperature.