| Spatial variation of soil moisture content under a sub-surface drip irrigated field was studied. Conventional statistics and geostatistical methods were used to analyze the relation between four soil variables: % sand, % silt, % clay, and soil moisture content. The soil moisture content was measured before, during, and after irrigation using tensiometers. The samples were collected from 63 sites on a 180 by 244 meters (4.45-hectare) cotton field. The pre- and post-irrigation soil moisture content shared the same spatial structure, differing only by the magnitude of their variances. After any irrigation the soil wetter points remained wetter and the drier points remained drier. It was found that the spatial patterns of soil moisture content appear to be stable over time. The ranges obtained from the variograms before and after an irrigation had the same magnitude of influence. The coefficient of uniformity obtained using the gravimetric method was 92.4 %, however, using tensiometers values ranged from 84.4 to 87.3%. |
