4. fertilisers and eutrophication

• crops take in minerals as they grow 2. crops removed, not left to die and decompose. mineral ions not returned to soil y decomposers

• animals eat grass/plants taking up nutrients 2. nutrients aren’t replaced

inorganic contain pure chemicals soluble. more likely to leach into waterways

organic manure, composted veg, crop residue, sewage sludge still contained in organic molecules that need to be decomposed. leaching less likely

• more fertiliser applied than needed • fertiliser leach into water ways (water soluble compounds in soil washed away e.g. by rain) -> eutrophication • too much of a nutrient can cause crops/plants to die

• mineral ions leached from fertilised fields. • stimulate rapid growth of algae in ponds and rivers • large amounts of algae block ligh reaching plants below • plants die (unable to photosynthesise) • bacteria feed on dead plants. • more bacteria = reduce oxygen in water through aerobic respiration • fish and other aquatic organisms die (not enough dissolved oxygen