ASABE Technical Library - Abstract
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Development of a Low-Cost Root Collar Diameter Measurement System for Pine Seedlings
Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan www.asabe.org
Citation: Paper number 035003, 2003 ASAE Annual Meeting . (doi: 10.13031/2013.14113) @2003Authors: Tony E. Grift
Keywords: Seedling, Root Collar Diameter, Measurement, Optical
To assess the growth stage of the crop in the field, every year seedling nurseries measure
the Root Collar Diameter (RCD) of a large number of seedlings. This is traditionally done manually
using a slide micrometer and registration of data on paper, a tedious and error-prone practice. As an
alternative, an optical system was developed that measures the RCD of a pine seedling semiautomatically.
As a proof of concept, a system was devised where objects of constant diameter were mounted on
the rim of a wheel spinning at a constant speed. The diameters of the objects were measured with
optical sensors, producing a maximum error of 2.85 %.
Two realistic versions of a semi-automatic RCD measurement system were developed, 1) a system
where the user slides the seedling along an edge and 2) a system where the user places the
seedling on a table after which the system measures and stores the RCD at the push of a button.
The first version produced errors less than 0.7%, sufficiently accurate, but operator dependent and
not very user-friendly. The second version had an accuracy better than 0.2%, virtually independent
of operator skill.
The concept of measuring the RCD on-the-fly using an optical method could be used to
develop a seedling yield monitor on a seedling harvester (lifter) in the near future, although
the transition from laboratory to field conditions will require redesign and intensive testing.