Agricultural Science II: Propagation, Breeding, Plant Physiology, Pest Management, Post-Harvest, and Paddy

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Plant Propagation

Sexual (seeds): seed quality, germination, dormancy-breaking, nursery management, seedling transplanting.
Asexual (vegetative): cuttings, layering, budding, grafting (rootstock and scion), tubers, corms, and runners, and tissue culture (micropropagation produces large numbers of disease-free plants from small tissue pieces).
Choose the method by crop, speed, cost, and genetic uniformity.

Plant Breeding

Goals: higher yield, quality, resistance to pests, diseases, and stresses, and adaptation.
Methods: selection (mass, pure line), hybridization and heterosis, mutation breeding, polyploidy, biotechnology (marker-assisted selection, genetic modification); varietal release and seed certification (basic, foundation, and certified seed).
Sri Lankan rice varieties are released by the Department of Agriculture and carry codes (such as Bg for Bombuwela, At for Ambalantota, and Bw for Batalagoda), with differing durations (about 3 to 4.5 months) and traits.
Principles from genetics (Chapter 11) underpin breeding.

Plant Physiology in Agriculture

Photosynthesis and respiration determine yield; transpiration and water relations; plant growth regulators (auxin for rooting, gibberellin for growth, ethylene for ripening); photoperiod and flowering; dormancy; and senescence. Understand how harvest index and crop growth rate relate to management.

Control of the Growing Environment

Protected cultivation (greenhouses, net houses, shade houses), mulching, windbreaks, hydroponics, and soilless culture adjust conditions for high-value crops.

Pest Management

Pests: insects, mites, nematodes, rodents, birds, weeds, and the pathogens (fungi, bacteria, viruses) causing plant diseases.
Integrated Pest Management (IPM): combines cultural control (crop rotation, resistant varieties, sanitation, timing), mechanical and physical control, biological control (natural enemies, biopesticides), chemical control (used judiciously), and legal control (quarantine), guided by monitoring and economic thresholds.
Pesticides: classes (insecticides, fungicides, herbicides); safe use (correct dose, protective clothing, pre-harvest intervals, safe storage and disposal); resistance development; residues in food and water; effects on non-target organisms.
Weed management: prevention, mechanical, cultural, and chemical methods.

Post-Harvest Technology

Maturity indices and harvesting; post-harvest losses (physical damage, respiration, transpiration, rot); handling and packaging; storage (temperature, humidity, controlled atmosphere); processing (drying, canning, juicing, milling, fermentation); value addition; food safety and quality standards; marketing and transport.

Home Gardens and Paddy Farming

Home gardens are multi-layered systems of trees, shrubs, and vegetables combined with livestock, providing food, income, and biodiversity; they are an important traditional system in Sri Lanka.
Paddy: the two seasons are Maha (about October to March, north-east monsoon) and Yala (about April or May to August or September); growth stages: vegetative (germination, seedling, tillering), reproductive (panicle initiation, booting, heading, flowering), and ripening (milk, dough, and mature grain). Practices: variety choice, land preparation, establishment (transplanting or direct seeding), nutrient and water management, weed, pest, and disease control, harvesting, threshing, drying, and storage.

Common Mistakes

Confusing grafting and budding terminology.
Treating chemical control as the first option in IPM.
Forgetting the pre-harvest interval for pesticides.

CHAPTER 23