1. Soils Workshop 2008 Soil Fertility Session 13 th August 2008 John Standley

2. 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

4. 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

6. 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

8. 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

9. 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?

11. 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

12. Nutrient removal Consider removal by various crops Consider fertiliser analyses and how much needs to be applied Consider manures See N-O5

15. 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

20. Deficiency symptoms What does the plant tell us?

24. 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

26. Nodulation Examine the roots of grasses and legumes Grow soybeans with and without rhizobial inoculum Examine nodules With and without N fertiliser See O-O7