crop plants

• glass house - artificial heating means enzymes are at optimum temp for photosynthesis, artificial lighting so plants can photosynthesise for longer, increasing carbon dioxide contents so plants can photosynthesise quicker, regular watering. however, there is a significant extra cost against the increased income. in hot countries, the greenhouses may need to be ventilated to avoid temps running too high
• polyethene tunnels - they protect crops grown outside from weather including wind and rain and temp. they also increase temperature slightly in the tunnel and they prevent the entry of any pests which can damage the plants
• how fertilisers increase crop yield - fertilisers contain a range of mineral ions which helps crops grow faster and bigger so crop yield increases (normally nitrogen, phosphorus and manure)
• organic fertilisers - used by farmers include farmyard manure and compost
• chemical fertilisers - often applied to soil as dry granules or can be sprayed on in liquid form
• advantages of pesticides - easily accessible and relatively cheap, have an immediate effect, kills the entire population of pests
• disadvantages of pesticides - resistance can be developed to them, they are non specific chemicals and can often kill other beneficial organisms, they can be persistent chemicals (do not break down in body and so can accumulate in great concentration at the top of the food chains and harm top predators), need to be repeatedly applied
• advantages of biological control - natural method, no resistance, can target specific species, long lasting, does not need to be reapplied
• disadvantages of biological control - may eat other organisms instead of the pest, takes longer period of time to be effective, cannot kill entire population, may not adapt to new enviroment, may become a pest itself