8 

 and none released more than 6 ppm of sulfate-S when incubated for 10 

 weeks under aerobic conditions. They found no significant correlation 

 between mineralized S and total S, sulfate S, organic C, total N, or 

 mineralized N. 



Bettany et al. (1980) found C:N:total S ratios of 79:7.9:1 in a 

 Udic Haploboroll under pasture and ratios of 71:6.6:1 for the same soil 

 that had been cultivated for 65 years in Saskatchewan. The relatively 

 narrower C:S and N:S ratios of the cultivated soil, along with a rela- 

 tively smaller decrease in S than both C and N in the cultivated soil, 

 suggested that S is more resistant to mineralization than C and N. 

 Earlier, they had found the largest amount of S mineralization occurred 

 in soils with the lowest C:N:S ratios (Bettany et al., 1974). 



Kowalenko and Lowe (19 75) concluded from their research that while 

 the interrelationships of C, N, and S would be important in a consid- 

 eration of the S supplying power of a soil, more complex interrelation- 

 ships than simple C:N:S ratios may exist. 

 1.1.2.2 Organic sulfur fractionation 



At the same time investigators were studying C:N:S relationships 

 in soils, many developed techniques to fractionate organic S to find 

 the form or forms of organic S that might influence 3 mineralization. 

 Williams and Steinbergs (1959) separated soil S into alkali-soluble S, 

 soluble sulfate after ignition, heat-soluble S, reducible S, and sul- 

 fate released by hydrogen peroxide oxidation. Each method removed part 

 of the organically-bound S, but only the heat-soluble fraction was 

 highly correlated with the amount of S taken up by plants. Heating 

 the soil on a water bath, followed by heating for 1 hour at 102°C in a 

 hot-air oven, released a maximum amount of S from the soil. Most of 



