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Author: Ian Miller, Grant Tranter and Anna Houston |
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The analysis of the data was competed on the JMP 5.1 statistical package. A one way ANOVA t-test was conducted for the penetration strength (kPa) by landuse. A one way analysis was conducted with the Time Domain Reflectrometry (TDR) and landuse to show the effects of water content and penetration strength (kPa). A predictive contour plot of penetrometer values was created by using Vesper (ACPA 2003). For description of analysis Click here. It should be noted where EM is written, penetrometer values were placed here.
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One way ANOVA t-test for Landuse and penetration strength (kPa) and TDR water content % The results show that the penetration strength between the pasture and cultivated land is significantly different with a p-value of <0.0001. The pasture area has a higher penetration strength with a mean of 411.0 kPa compared to the cultivated area with a mean of 155.5 kPa. The TDR results indicated the cultivated area had a higher water content therefore reducing the strength of the soil, the cone penetrometer was able to compress and shear the soil with ease. This clear representation of the results obtained from the total field survey can also be shown in the 10 site locations, where by the water content (influenced by landuse) clearly influences the penetrability of the cone.
Contour plot of predicted cone penetrometer values (kPa)
The predicted values show a clear divide between the landuses, where the majority of the field has a low penetrability strength, this represents the cultivated land. The area above the cultivated land with a higher penetrability is the pasture. The blue area which has a higher value therefore low water content is possibly due to the trees drying the soil, field observation would have been beneficial as the ground cover would be variable causing the water content to differ. The two oval areas in the cultivated land may be due to the depression of the land, human error or use of the land in the past. Over all the contour plot gives a clear representation of the landuse and how it effects the penetrability strength, cultivated land will have a lower strength compared to pasture land.
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To understand the issues associated with the dynamic cone penetrometer Click here. McKenzie N, Coughlan K and Cresswell H. (2002) Soil Physical Measurement and Interpretation for Land Evaluation. (CSIRO Publishing: Melbourne).
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