18.11.2012 Views

Cranfield University

Cranfield University

Cranfield University

SHOW MORE
SHOW LESS

You also want an ePaper? Increase the reach of your titles

YUMPU automatically turns print PDFs into web optimized ePapers that Google loves.

Field Study With Full Size Combine Harvesters<br />

Analyzing the interaction of treatment and group is shown in Table 22. Due to the large<br />

variances the amount of significant differences was small, but the trends agreed with pre-<br />

vious data in this chapter, the thesis and in Ansorge (2005, a).<br />

Table 22: Estimated DBD for treatments and controls, statistically identical DBD<br />

followed by the same letter<br />

Effect Estimated DBD (g/cc) SE DF<br />

Control Clay 1.271 a 0.034 29<br />

Control Sandy Loam Shallow Tilled (SLT) 1.463 b 0.034 29<br />

Control Sandy Loam Subsoiled (SLS) 1.323 a 0.034 29<br />

High Inflation Pressure on Clay 1.318 a 0.042 29<br />

High Inflation Pressure on SLT 1.563 c 0.034 29<br />

High Inflation Pressure on SLS 1.672 d 0.034 29<br />

Normal Inflation Pressure on Clay 1.349 a 0.030 29<br />

Normal Inflation Pressure on SLT 1.597 c e 0.030 29<br />

Normal Inflation Pressure on SLS 1.605 d e 0.030 29<br />

Tracked Machine on Clay 1.333 a 0.030 29<br />

Tracked Machine on SLT 1.581 c e 0.030 29<br />

Tracked Machine on SLS 1.582 d e 0.030 29<br />

The moisture content on the clay site was 36 % and on the sandy loam subsoiled part 20.5<br />

% and the shallow tilled part 21.5 %.<br />

4.1.5 Density Measurements with Nuclear Density Gauge<br />

Figure 62 shows the DBD before and after the passage of tracked, wheeled and high in-<br />

flated wheeled combine harvesters in the field on the different field sites. Statistically ac-<br />

counting for treatment and depth was significant in explaining the variation. There was no<br />

interaction between depth and treatment, showing for all treatments a similar behavior with<br />

depth. Figure 62 a) shows the results for the clay soil where the DBD for the control was<br />

in tendency higher than after the passage of the machines. Apart from the machine at high<br />

inflation pressure the control and the passage were not significantly different from each<br />

other however, the experiment has a smaller value than the control. This was interesting as<br />

it would mean that driving over the soil with a combine harvester would in fact loosen the<br />

soil. As this was not possible, it could only be due to the swelling of the clay caused by<br />

Ph.D. Thesis Dirk Ansorge (2007)<br />

78

Hooray! Your file is uploaded and ready to be published.

Saved successfully!

Ooh no, something went wrong!