Use a soil-testing kit to find out how pH and nutrient (nitrogen and potash) content of soils vary. Investigate the effect of soil pH on crops.
See a useful table at www.ruralni.gov.ukcropsvegetablestechnical_informationsoil.htm
Explain the role of microbes in the nitrogen cycle and why using artificial and natural fertilisers has affected its natural balance. Use the Fens and Norfolk Broads to show how fertiliser "run-off" has caused eutrophication in the waterways and its effect on wildlife. See BTCV handbooks on line at handbooks.btcv.org.uk
Consider the structural adaptations of halophytes and xerophytes. Explain the osmotic processes which help halophytes survive in salt marshes.
Compare their physiological adaptations with those found in xerophytes.