A large portion of the U.S. Green Industry is involved with growing plants in containers, including nursery crops, annual bedding plants and potted herbaceous perennials. With such a large portion of the industry in containers, it is important to understand the factors that influence root growth to attain optimal benefits from container production. Several factors that affect root growth include the physical and chemical properties of substrates. Physical properties include porosity and water holdingcapacity, percentage of fine particles and bulk density (Mathers et al., 2007). Chemical properties include pH, cation exchange capacity and soluble salts (Mathers et al., 2007). There are several known techniques used to measure these factors that affect root growth, but methods used to measure the whole root system or measure the growth of roots over time are not as widely available. It is also not well understood how roots change and affect the physical properties of substrates in the container overtime. The most common root system measurements reported in scientific literature are: (1) subjective root ratings and (2) root dry weight measurements. Root ratings, while being non-destructive, are completely subjective to the person rating the root system and can vary person to person. The second method of root washing is widely accepted as a valid determination of root mass but it is well understood/assumed that a percent of root (particularly fine roots) mass is lost. Oliveira et al. (2000) reported that almost 20-40% of the original root weight is lost during root washing of certain plant species.
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