Across
- 3. compacts the soil, limiting the infiltration of water and air into the soil.
- 5. disturbance upsets the balance of the ecosystem
- 6. caused by over-irrigation in arid regions where evaporation is rapid. High levels of salt in the soil kill crops and reduce land productivity.
Down
- 1. a phenomenon caused by nutrients in waste that encourage the rapid growth of algae, which consume oxygen in the water.
- 2. caused by over-irrigation of the soil. Many crops die from lack of oxygen.
- 4. species that grow rapidly, stimulated by nutrients in the residues.