Sulphur is an important nutrient within the soil solution. It is needed by plants for protein synthesis, certain vitamins and enzymes that transfer energy and to stimulate nitrogen fixation (Cameron and McLaren, 1996). Where there is a sulphur deficiency plants are small and thin, with a decreased growth rate and delayed maturity. Sulphur is taken up by plants in the inorganic sulphate ion, but the majority of sulphur within the soil occurs in the organic form (Goh and Nguyen, 1994). Sulphur in soil comes from weathering of parent material, types of vegetation, atmospheric inputs and decaying plant matter (Brady and Weil, 1996). Because of this, temperature and precipitation can have an effect on sulphur levels, particularly through leaching of the soluble sulphate ions in winter. Sulphur levels are also connected to nitrogen levels in soil organic matter, as the ratio between the two is fixed within plant proteins (Cameron and McLaren, 1996; Goh and Nguyen, 1994).
Because of the need of sulphur for optimal plant growth, the levels of sulphur within dairy farms is important in producing as much pasture for milk production as possible. The addition of sulphur as elemental S or sulphate ions through fertiliser is common practice in New Zealand (Cameron and McLaren, 1996). Farming practices such as irrigation and stock trampling may also have an effect on sulphur levels within the soil on dairy farms (Brady and Weil, 1996).
The aim of this report is to test for any statistically significant changes in sulphur concentration on a dairy farming. This will be carried out by testing a soil from a dairy farm on the Taieri Plains of Otago and a control soil from nearby with no dairy farming processes operating on it. Total inorganic and organic sulphur concentrations will be tested. The dairy soil was taken from near cattle yards, where livestock are often walking across the soil, while the control was from a roadside with native grasses growing on it. It is hypothesised that the sulphur levels within the dairy soil will decrease compared to the control, as plant uptake is high through constant growing of pasture, leaching through rainfall and loss through waterlogging of soil. This report will investigate any changes within sulphur concentrations and why they may occur. Results
The data collected was corrected for any additional sulphur added during testing and a moisture factor. As seen in table 1, the mean of the control sulphur is much larger than that of the dairy, 37.964 and 10.724 respectively.
Table 1: Summary statistics for corrected Sulphur concentration (ppm) in the control and dairy soils
Mean
Standard Deviation
Median
Variance
Minimum
Maximum
Range
Control S
37.964
1.157
38.241
1.339
35.675
39.498
3.823
Dairy S
10.724
1.211
10.836
1.466
8.366
13.302
4.936
Shown below in figure 1 is the corrected data values plotted graphically. As seen there is little spread within the separate data sets and a wide gap between the two sets. No outliers occur.
Figure 1: Dotplot of the collected data for sulphur concentration in the dairy and control soils
The mean value of the dairy sulphur falls into the adequate section of nutrient soil levels, while the control is in the very high (Department of Environment and Primary Industries Victoria).
The data was statistically analysed to test if the difference between concentrations was significant. A T-test was used as the variances were equal and there were no outliers in the data (Fcalc = 1.095). This showed a significant difference as (p=0.000) and the 95% confidence interval excluded 0 (26.352, 28.127).
Discussion
The data collected supported the original hypothesis of a decrease in sulphur concentration on the dairy soil, confirmed by statistical analysis to be a significant decrease. This decrease is likely to be due to human activities on the soil, in the form of leaching, stock trampling, increased
