Keywords: pedotransfer functions, soil hydraulic properties, SWBACROS, irrigation scheduling, functional evaluation.

Computer simulation of the complex soil-plant-atmosphere continuum, has been proven to be an effective process in addressing environmental problems. A major drawback is the requirement of a substantial amount of input data. In addition to that, many inputs, such as the soil hydraulic properties, are both extremely variable in space and time and time consuming to obtain [1,2], thus the cost of field data collection is significantly raised.

Although indirect estimation of soil hydraulic properties by pedotransfer functions (PTFs) [3], seems to be an alternative solution to field data collection, the effects of using PTFs on soil water balance simulation are not often examined. This paper attempts to provide an insight to the efficiency of PTFs to correctly describe the soil water content variations of a cropped field, as well as on how they affect irrigation scheduling.

For this purpose, field data from two different crops (sugarbeet and cotton) and PTFs suggested by [4] are used. Simulations were carried out using the SWBACROS model [5,6]. Comparison between soil moisture characteristics (SMCs) constructed with PTFs and the SMCs determined in the laboratory revealed that, differences may exist within the pressure range between 0.1m to 150.0m, but significant differences were found in only one case (0-50cm layer of the sugarbeet field). The use of PTFs in general overestimated the soil water content observed. Higher discrepancies were observed at the top soil layers, which are diminishing in deeper layers. Irrigation scheduling based on PTFs, was clearly affected by the aforementioned discrepancies. By continuously predicting higher soil water contents, PTFs reduced the total number of irrigation events and total irrigation depth.

With pedotransfer functions being an such attractive alternative to field data collection, further research should be made in order to obtain more reliable results when PTFs are used.

1

A.B. McBratney, B. Minasny, S.R. Cattle, R.W. Vervoort, "From pedotransfer functions to soil inference systems", Geoderma, 109, 41-73, 2002. doi:10.1016/S0016-7061(02)00139-8

2

L. Baker, "Development of class pedotransfer functions of soil water retention - A refinement", Geoderma, 144, 225-230, 2008. doi:10.1016/j.geoderma.2007.11.017

3

J. Bouma, "Using soil survey data for quantitative land evaluation", Advances in Soil Science, 9, 177-213, 1989.

4

A.G. Mousouliotis, H. Georgoussis, Ch. Babajimopoulos, A. Panoras, E. Hatzigiannakis, G., Arampatzis, "Use of pedotransfer functions for the description of soil hydraulic properties in the Thessaloniki plain: II Development of new functions", Proceedings of the common 11th Panhellenic Congress of the Hellenic Hydrotechnical Association and the 7th National Conference of the Greek Committee for Water Resources Management, Volos, Greece, 2009 (accepted for publication - in Greek).

5

C. Babajimopoulos, A. Budina, D. Kalfountzos, "SWBACROS: A model for the estimation of the water balance of acropped soil", Environmental Modelling Software, 10(3), 211-220, 1995.

6

C. Babajimopoulos, "Revisiting the Douglas-Jones method for modelling unsaturated flow in cultivated soil", Environmental Modelling Software, 15, 303-312, 2000. doi:10.1016/S1364-8152(00)00019-0

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