Soil Carbon
• Labile carbon – oxidised with dilute potassium permanganate; the fraction changing most rapidly
• Organic carbon – oxidised by potassium dichromate in sulphuric acid; about 70% of total carbon
• Total carbon – converted to carbon dioxide at high temperature; may include carbonate
Organic carbon in soils
• Comparisons - surface and subsoil
• Different soils
• Uncleared land or by trees
• Under pasture or lawn
• In cultivated paddocks or gardens
• Bare soil
• See S-O3, S-O4
Soil pH and liming
• Some soils may be too acid for some plants
• Adjust pH by adding lime. Does gypsum have the same effect?
• Compare the three soils without and with the addition of lime
• Experiment with different rates• See S-O6
Fertilisers and pH
• Compare ammonium sulphate, ammonium nitrate, potassium nitrate and urea
• Check the effect of urea on the three soils
• Experiment with your soils
• See N-O6
Urea changes
• Expect urea to be converted ammonium to make soils more alkaline
• Expect ammonium to be converted to nitrate
• Check what has happened with the three soils
• Beware of units – measuring N (14) or NO3 (62) ppm?
Fertiliser experiments
• Grow various plants with various fertilisers and record what happens
• Compare rates and plot growth response curve
• Maybe in conjunction with maths teacher run a replicated trial, fertiliser rates replicated three or four times to separate treatment and environmental effects
Nutrient removal
• Consider removal by various crops
• Consider fertiliser analyses and how much needs to be applied
• Consider manures
• See N-O5
Manure composition
• An example
• Cattle manure from feedlots
• Nitrogen 2%
• Phosphorus 0.8%
• Potassium 2.3%
• Compare with inorganic fertilisers and calculate how much will be required
Mycorrhizae
• Have a look
• Experiment with linseed in pots
• Soil “as is”, sterilised , with and without inoculum added
• Also with and without P fertiliser
• Could consider zinc too
• See O-O6