A method to separate plant roots from soil and analyze root surface area

Abstract

Analysis of the effects of soil management practices on crop production requires knowledge of these effects on plant roots. Much time is required to wash plant roots from soil and separate the living plant roots from organic debris and previous years' roots. We developed a root washer that can accommodate relatively large soil samples for washing. The root washer has a rotary design and will accommodate up to 24 samples (100 mm diam. by 240 mm long) at one time. We used a flat-bed scanner to digitize an image of the roots from each sample and used a grid system with commercially-available image analysis software to analyze each sample for root surface area. Sensitivity analysis and subsequent comparisons of 'dirty' samples containing the roots and all the organic debris contained in the sample and 'clean' samples where the organic debris was manually removed from each sample showed that up to 15% of the projected image could be covered with debris without affecting accuracy and precision of root surface area measurements. Samples containing a large amount of debris may need to be partitioned into more than one scanning tray to allow accurate measurements of the root surface area. Sample processing time was reduced from 20 h, when hand separation of roots from debris was used, to about 0.5 h, when analyzing the image from an uncleaned sample. The method minimizes the need for preprocessing steps such as dying the roots to get better image contrast for image analysis. Some information, such as root length, root diameter classes and root weights, is not obtained when using this technique. Root length measurements, if needed, could be made by hand on the digital images. Root weight measurement would require sample cleaning and the advantage of less processing time per sample with this method would be lost. The significance of the tradeoff between information not obtained using this technique and the ability to process a greater number of samples with the time and personnel resources available must be determined by the individual researcher and research objectives.

Fine-root carbon and nitrogen concentration of European beech (Fagus sylvatica L.) in Italy Prealps: possible implications of coppice conversion to high forest

“…Various studies show that increase in canopy gap size causes an increase of both seasonal average soil temperatures and soil temperature extremes (Liechty et al, 1992; Hashimoto and Suzuki, 2004). Moreover, seasonal and diurnal differences in maximum-minimum air temperatures increase 15 cm above soil surface as well (Carlson and Groot, 1997). …”

Quantification of roots and seeds in soil with real-time PCR

“…When roots are separated from soil, fine roots are lost, distinguishing dead roots is difficult (Oliveira et al 2000) and it is not possible to reliably separate different species or readily study associated soil biota. Improvements in efficiency of extraction and estimation continue to be made (Benjamin and Nielsen 2004;Blouin et al 2007;Metcalfe et al 2007a, b) and the difficulties of interpreting such results without understanding of anatomy and structure has been recently highlighted (Watt et al 2008). Additionally, Atkinson (2000) emphasises there is a need to reconcile root measurement with function.…”

A quick method to determine root biomass distribution in diameter classes

“…Soil and root separation takes 20 min: washing coarsely (5 min), cutting (5 min) and differential sedimentation (10 min). This was shorter than with the automatic washing mechanism described by Benjamin and Nielsen (2004), which requires 90 min. However, this was longer than the hydropneumatic elutriation system which requires 3-10 min according to soil texture and plant species, but concerns only small soil cores between 115 and 825 cm 3 (Smucker et al 1982).…”

“…First, the root system can be washed very quickly, even coarsely; remaining soil particles or dead organic matter will be separated from root pieces after cutting, by differential sedimentation. This avoids the use of complex root/soil separation devices (Smucker et al 1982;Benjamin and Nielsen 2004). Soil and root separation takes 20 min: washing coarsely (5 min), cutting (5 min) and differential sedimentation (10 min).…”