Document Type : Research Paper

Authors

• A Khorasani
• M.A Mousavi Shalmani
• N Piervali Bieranvand

Abstract

An accurate, precise, fast and ease as well as the ability for measurements in depth are the characteristics that are desirable in measuring soil moisture methods. To compare methods (time domain reflectometry and capacitance) with neutron scattering for soil water monitoring, an experiment was carried out in a randomized complete block (RCB) design (Split Split plot) on tomato with three replications on the experimental field of IAEA (Seibersdorf-Austria). The treatment instruments for the soil moisture monitoring (main factor) consist of neutron gauge, Diviner2000, time domain reflectometer (TDR) and an EnviroScan and different irrigation systems (first sub factor) consist of trickle and furrow irrigations and different depths of soil (second sub factor) consist of 0-20, 20-40 and 40-60cm. The results showed that for the neutron gauge and TDR the amount of soil moisture in both of trickle and furrow irrigations were the same, but the significant differences were recorded in Diviner2000 and EnviroScan measurements. The results of this study showed that the neutron gauge is an acceptable and reliable means with the modern technology, with a precision of ±2mm in 450mm soil water to a depth of 1.5 meter and can be considered as the most practical method for measuring soil moisture profiles and irrigation planning program. The TDR method in most mineral soils, without the need for calibration, with an accuracy ±0.01m³m^-3 has a good performance in soil moisture and electrical conductivity measurements. The Diviner2000 and EnviroScan are not well suitable for the above conditions for several reasons such as much higher soil moisture and a large error measurement and also its sensitivity to the soil gap and to the small change in the soil moisture in comparison with the neutron gauge and the TDR methods.

Highlights

1. T. Kovacs, G. Kovacs, J. Szito, “Crop yield response to deficit irrigation imposed at different plant growth stages,” IAEA-TECDOC-888, 89-114 (1996).

    

2. T.J. Dean, J.P. Bell, A.J.B. Baty, “Soil moisture measurement by an improved capacitance technique: Part 1. Sensor design and performance,” J. Hydrol. 93, 67-78 (1987).

 

1. D.K. Das and Bandyopadhyay,s “Soil water management and crop water use studies using nuclear techniquse. 17^th World Congress of Soil Science,” Volome V Symposium, 59, 1778 (2002).

 

1. F. Moreno, F. Pelegrin, J.E. Fernandez, J.M. Murillo, “Measurement of soil water content using TDR and the neutron probe in tillage experiments in semi-arid SW Spain,” IAEA-TECDOC-1137, 105-110 (2000).

 

1. S. Evett, J.P. Laurent, P. Cepuder, C. Hignett, “Neutron scattering, capacitance, and TDR soil water content measurements compared on four continents. 17^th World Congress of Soil Science,” Volome V Symposium, 59, 1021 (2002).

 

1. “Water balance and Fertigation for crop improvement in west Asia,” IAEA–TECDOC, 1266 (2002).

 

1. O.O.S. Bacchi, K. Reichardt, M. Calvache, “Neutron probes and Their use in agronomy,” IAEA Training course series, IAEA (2001).

 

1. C.S.R. Hignett, Evett, “Neutron thermalization. Accepted for publication. In Methods in Soil Analysis, Part 1,” Physical and Mineralogical Methods, 3^rded. Agronomy Monograph Number 9 (2002).

 

1. S.R. Evett and J.L. steiner, “Precision of neutron scattering and capacitance type soil water content gauges from field calibration,” Soil. Sc. Soc. Of Am. J. 59, 961-968 (1995).

 

1. G.C. Topp, J.L. Davis, A.P. Annan, “Electromagnetic determination of soil water content measurement in Coaxial transmission lines,” Water Resour. Res. 16, 574-582 (1980).

Keywords

• Irrigation
• Soil Moisture
• Neutron Gauge
• TDR
• Diviner2000
• EnviroScan