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SCHRIFTENREIHE Institut für Pflanzenernährung und Bodenkunde ...

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causes a platy soil structure (Krümmelbein et al., 2006). The relatively high Ks in<br />

HG is again associated with the coarser soil texture. However, despite the<br />

similar sandy texture, Ks is nearly twice higher in UG 79 than in HG, which is<br />

attributed to not only the higher fraction of large pores but an improved pore<br />

continuity of the more structured soil in the former.<br />

Table 5.3. The laboratory-derived hydraulic parameters (θr=residual water content,<br />

θs=saturated water content, α=reciprocal value of air entry pressure, n=the<br />

smoothness of pore size distribution and m=1-1/n), and Ks=saturated hydraulic<br />

conductivity) for the four sites (R 2 is determination coefficient fitted by RETC<br />

software).<br />

Treat- θr θs α n R 2 Ks<br />

Soil depth<br />

ment (cm) (cm 3 cm -3 ) (cm 3 cm -3 ) (cm -1 (cm<br />

) (-)<br />

day -1 )<br />

UG 79 4-8 0.075 0.572 0.026 1.766 0.983 165.0<br />

18-22 0.086 0.472 0.019 2.199 0.985 133.3<br />

30-34 0.079 0.453 0.015 2.549 0.986 113.7<br />

40-44 0.071 0.452 0.016 2.120 0.985 71.9<br />

UG 99 4-8 0.086 0.577 0.022 1.628 0.983 82.3<br />

18-22 0.096 0.526 0.020 1.750 0.988 66.7<br />

30-34 0.102 0.506 0.017 1.940 0.996 57.1<br />

40-44 0.107 0.502 0.016 2.241 0.992 54.3<br />

WG 4-8 0.075 0.570 0.021 1.636 0.996 54.7<br />

18-22 0.050 0.526 0.023 1.616 0.994 69.8<br />

30-34 0.072 0.529 0.012 1.791 0.969 72.7<br />

40-44 0.079 0.517 0.014 1.742 0.981 61.3<br />

HG 4-8 0.057 0.523 0.014 1.718 0.982 93.0<br />

18-22 0.049 0.473 0.013 2.030 0.983 92.7<br />

30-34 0.060 0.479 0.012 2.130 0.982 75.9<br />

40-44 0.058 0.453 0.013 2.108 0.987 79.4<br />

Soil Moisture and Temperature Regimes<br />

Fig. 2 shows contour plots of depth-averaged soil moisture and temperature<br />

in the four sites during the growing period in 2006. Soil moisture decreases with<br />

increasing soil depth from May to July for all sites, indicating low water storage in<br />

deeper soil layers. However, a reverse trend is observed from late July to<br />

September except for HG, indicating high plant water demands. Compared with<br />

96

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