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Lysimetry versus Neutron Moisture Meter for Evapotranspiration Determination in Four Soils
Author(s) -
Tolk Judy A.,
Evett Steven R.
Publication year - 2009
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj2009.0037
Subject(s) - loam , lysimeter , soil water , evapotranspiration , environmental science , irrigation , water balance , water content , hydrology (agriculture) , drainage , surface runoff , moisture , soil texture , soil science , geology , geography , agronomy , geotechnical engineering , ecology , biology , meteorology
Knowledge of evapotranspiration (ET) is vital for the management of our freshwater resources. One method for determining ET is through the measurement of the soil water balance, where ET is the residual calculated from the change in soil water storage plus precipitation and irrigation and minus drainage and runoff. The objective of this research was to compare the ET calculations where the change in soil water storage was measured using the neutron moisture meter (NMM), or ET NMM , vs. using weighing lysimeters (ET LYS ) in four soils. Cotton ( Gossypium hirsutum L.) was grown in 2006 and 2007 in weighing lysimeters with NMM access tubes and drainage systems. The soil textures ranged from fine sand to clay loam. The ET NMM was ≤4% of the ET LYS for the clay loam and sandy loam soils, but ET NMM was 8% less than ET LYS in the fine sand due to errors created by the timing of drainage and NMM measurements. At ET LYS amounts <50 mm, the difference between ET LYS and ET NMM for individual measurement intervals could be as much as 28 mm and the average ET NMM /ET LYS ratios as much as 1.20. Beyond 100 mm of ET LYS , the average ET NMM /ET LYS ratios became near 1.0 except for the fine sand, where unmeasured drainage out of the NMM sensor zone resulted in an underestimation of ET. When all other soil water balance components were quantified, a field‐calibrated NMM accurately determined the change in soil water storage for the calculation of ET in three of the four soils.