Explanation:
(a)Definition of nursery in crop production: Nursery is a place where young plants are raised under intensive management practices for later transplanting into permanent fields/plot
(b)Reasons for establishing a nursery in crop production
- Promotes economy of seeds/efficient utilization of seeds
- Seedlings receive more intensive care e.g watering manuring and protection from animals, disease and pests
- Creates an opportunity for selecting healthy, vigorous and disease-free seedlings for transplanting
-Seeds that ate difficult to germinate in the field are better raised in the nursery e.g carrot, cabbage.
- Horticultural practices like budding, grafting are easily carried out in the nursery
- It is place for hardening delicate seedlings before transplanting them
(c)Characteristic of weeds that make them difficult to control
- Ability to produce many seeds
- Weed seeds have long period of dormancy
- Some weeds have deep root systems used for absorbing water from deeper horizons in dry soils
- Some weeds have modified root system for storing food which they thrive on for long periods e.g waterleaf
- A good number of weeds have very efficient means of dispersal
- Weeds survive under marginal/poor soil by virtue of profuse rooting systems and their minimum nutrient requirement status
- Some weeds have very fast growth rates
- Weeds survive under adverse environmental conditions by means of structures such as stolon, rhizomes
(d)Methods of controlling weeds
- Physical/Mechanical control
- Chemical control
- Biological control Cultural control
(e)Ways by which diseases are spread among crops
- Wind
- Water
- Contact(animal and human)
- Infected/diseased planting materials
- Infected soils
- Vectors
- Contaminated farm tools
(f)Effects of diseases on crops
- Reduced yield/output
- Reduction in the quality of produce
- Malformation of plant parts (gall formation, reduction in the leaf area)
- Death of plants
- Retarded growth of crops
- Reduced seed viability
- Deterioration of stored produce