تخمين منحني رطوبتي خاك نزديك اشباع با استفاده از اطلاعات نفوذ سنج ديسك و مقايسه آن با روش آزمايشگاهي

Estimating near-saturated soil moisture curve using disc-permeameter data and comparing it with laboratorial method

The hydraulic properties of soil, such as soil moisture characteristic and pore size distribution, are very important for the interpretation of the physical characteristics of soil and the management of agriculture practices. The current standard methods employing pressure chamber and sandy box, however, are often time-consuming and difficult to carry out. In this study, a simple approach is proposed to estimate the soil moisture retention, with sufficient accuracy, using steady-state infiltration data. First, the steady state infiltration rates were measured alternatively in the tensions of -15, -10, -6, -3 and zero cm using a disc-permeameter. Then, for estimating hydraulic conductivity in the above tensions was used Elrick and Reynolds (1991) steady state analysis. Optimized saturated hydraulic conductivity obtained of field measurements was used as a initial parameter for the Brooks-Corey model fit to obtain the water retention parameters dec and b. The parameters were estimated with high accuracy (R2 >0.9) via fitting linear form of Brooks-Corey equation to data pairs of (k,h) using statistical software of SPSS 11. The estimated moisture curves at the two methods; Sandy box and proposed method; were compared. The estimated values to proposed method obtained less than the values that were estimated with laboratorial method.