Effect of tillage treatments on soil thermal conductivity for some Jordanian clay loam and loam soils

Soil thermal conductivity determines how a soil warms or cools with exchange of energy by conduction, convection, and radiation. The ability to monitor soil thermal conductivity is an important tool in managing the soil temperature regime to affect seed germination and crop growth. In this study, the temperature-by-time data was obtained using a single probe device to determine the soil thermal conductivity. The device was used in the ®eld in some Jordanian clay loam and loam soils to estimate their thermal conductivities under three different tillage treatments to a depth of 20 cm. Tillage treatments were: notillage, rotary tillage, and chisel tillage. For the same soil type, the results showed that rotary tillage decreased soil thermal conductivity more than chisel tillage, compared to no-tillage plots. For the clay loam, thermal conductivity ranged from 0.33 to 0.72 W mÿ1 Kÿ1 in chisel plowed treatments, from 0.30 to 0.48 W mÿ1 Kÿ1 in rotary plowed treatments, and from 0.45 to 0.78 W mÿ1 Kÿ1 in no-till treatments. For the loam, thermal conductivity ranged from 0.40 to 0.75 W mÿ1 Kÿ1 in chisel plowed treatments, from 0.34 to 0.57 W mÿ1 Kÿ1 in rotary plowed treatments, and from 0.50 to 0.79 W mÿ1 Kÿ1 in no-till treatments. The clay loam generally had lower thermal conductivity than loam in all similar tillage treatments. The thermal conductivity measured in this study for each tillage system, in each soil type, was compared with independent estimates based on standard procedures where soil properties are used to model thermal conductivity. The results of this study showed that thermal conductivity varied with soil texture and tillage treatment used and that differences between the modeled and measured thermal conductivities were very small. # 2000 Elsevier Science B.V. All rights reserved.