Publications
Author: Steven O. Link
Published: September 14, 2026
Journal: Agronomy, Volume 16, Article 1803
DOI: 10.3390/agronomy16181803
Keywords: Phenotyping, dendrometer, agriculture, electronic instrumentation, tubers, signal processing, growth, water status
Summary
Real-time measurement of belowground tuber growth has not been conducted in field crops. Studies were conducted in pivot-irrigated potato fields. In 2025, in a commercial agricultural field in Franklin County, Washington, a strain-gauge sensor was used to monitor the growth of a single Shepody tuber and estimate its daily water loss. Over the 11 days preceding harvest, tuber thickness increased by 0.8 mm, corresponding to a daily gain of 1.4 g, or a 4.2% increase. The greatest diurnal fluctuation was 0.439 mm, corresponding to a transpirational water loss of 9.1 mL, or 2.9% of the tuber’s water content. Daily estimated transpiration showed a positive correlation with estimated vapor pressure deficit.
In 2026, at the Washington State University Research Potato Farm, strain gauges and linear potentiometers were used to monitor Clearwater Russet tuber growth and diurnal variation. The linear potentiometers exhibited the expected patterns over periods of time but had lower resolution than the strain gauges. The strain gauges successfully measured the tubers over a period of 56 days. A large tuber (210 g) increased in thickness by 3.3 mm, while a smaller tuber (95 g) increased by 2.45 mm. Both tubers exhibited varying growth rates and increased in size after the vegetative stalks were cut for curing before harvest. These sensors may enable more precise input control and higher temporal resolution than current methods for belowground crops, supporting new research, improved crop management, yield prediction, and harvest decisions.
Author: Steven O. Link
Published: Preprints.org, July 2026
DOI: 10.20944/preprints202607.1396.v1
Keywords: phenotyping, dendrometer, agriculture, electronic instrumentation, tubers, signal processing, growth, water status
Research Areas: Precision Agriculture, Plant Phenotyping, Plant Water Status, Irrigation Management, Agricultural Sensors, Potato Production
Summary:
Measuring the growth of underground crops in real time has long been a challenge, since soil interferes with the sensors normally used above ground. This study tested a strain-gauge sensor, buried alongside a potato tuber in a working Washington State field, to track its growth and water loss continuously over the two weeks before harvest. The sensor detected steady daily growth and small day-to-night thickness changes tied to water movement in and out of the tuber — with water loss rising on hotter, drier days. The findings point toward a practical new tool for real-time yield estimation, irrigation timing, and harvest-quality decisions for potatoes and other below-ground crops.
Authors: Steven O. Link, Michael E. Thiede, R. Dave Evans, Janelle L. Downs, Glendon W. Gee
Published: 1994, USDA Forest Service, Intermountain Research Station — Proceedings: Wildland Shrub and Arid Land Restoration Symposium (Gen. Tech. Rep. INT-GTR-315), pp. 196–201
Keywords: sagebrush, hopsage, water stress, stem diameter, xylem pressure potential, arid land shrubs, ecophysiology
Research Areas: Plant Water Stress, Plant Physiology, Desert Ecology, Water Relations, Stem Diameter Monitoring, Ecophysiology, Precision Agriculture Foundations
Summary:
This study compared how two desert shrubs, big sagebrush and spiny hopsage, cope with the dry summers of the Hanford region in southeastern Washington. Researchers tracked leaf area, stem diameter changes, and water status in both species from early spring through summer as water stress built up. Big sagebrush, which keeps some of its leaves year-round, put on more overall growth than spiny hopsage, a shrub that drops all its leaves under drought. Spiny hopsage reached much lower internal water potential by midsummer, a sign of greater water stress, yet both shrubs kept functioning at these low levels. Stem thickness in both species swelled after rainfall and shrank as the season dried out, showing that stems act as small water reservoirs the plants can draw on.The two species also responded almost identically in terms of photosynthesis, both slowing down as summer stress increased. The findings suggest spiny hopsage survives dry summers by pulling more water from the soil and tolerating harsher internal water stress, while big sagebrush relies on steadier, more moderate water use to sustain its evergreen growth habit.
Authors: Steven O. Link, Michael E. Thiede, M.G. van Bavel
Published: Journal of Experimental Botany, Vol. 49, No. 326, pp. 1583–1587, September 1998
Keywords: strain gauge dendrometer, plant stem and fruit thickness sensor, plant water status, growth
Summary:
This paper introduces an improved version of a sensor used to track tiny changes in the thickness of tree trunks and fruit over time. Earlier versions of these sensors (called dendrometers) worked well but had a limited range before needing to be manually reset, which made them awkward to use on fast-growing tissue like fruit. This redesign used a more flexible steel band, allowing it to measure a much wider range of thickness change without needing to be adjusted as often.
Tested on apple trees in an orchard in Mattawa, Washington, the sensor tracked two tree trunks and one apple fruit continuously over 15 days. The results showed a very clear and useful pattern: tree stems got thinner during the day and thicker at night, tracking the tree’s water use and recovery cycle, while the apple itself grew steadily, expanding by 3.3 millimeters over the two weeks, with only mild daily shrink-and-swell of its own. The study also carefully measured how much temperature alone could throw off the sensor’s readings, so that effect could be corrected for and true water-related changes could be seen clearly.
In short, this paper is about building a better, more practical tool for something growers care about deeply: understanding exactly when and how much a tree or its fruit is gaining or losing water, in real time, out in a working orchard rather than a lab.