Non Technical Summary
Water potential is critical to guide irrigation timing and quantity, dramatically affecting crop yield, quality, and water use efficiency. Growers lack tools to measure water potential accurately, automatically, and long-term, leading to preventable crop losses and excess water use. FloraPulse has demonstrated the only sensor that meets these requirements, a microtensiometer that directly measures water potential in the plant stem, but the current installation method is too large for a majority of commercial crops (i.e., corn, cotton, blueberry, etc.).We aim to develop an installation method that is 10x faster, easier, and dramatically smaller to allow widespread water potential measurement in small crop stems; as part of this effort, we will also survey crop wounding response to sensor installation and validate the small-stem installation method in the laboratory and commercial farms. This small-stem sensor will enable realtime water potential measurement in crops worth over $500 billion worldwide and could lead to 20% yield increases and 50% water savings.

Classification

Knowledge Area (KA)	Subject of Investigation (SOI)	Field of Science (FOS)	Percent
111	1219	2020	33%
404	1119	2020	33%
102	1212	2020	34%

Knowledge Area
102 - Soil, Plant, Water, Nutrient Relationships; 111 - Conservation and Efficient Use of Water; 404 - Instrumentation and Control Systems;

Subject Of Investigation
1119 - Deciduous tree fruits, general/other; 1212 - Almond; 1219 - Edible tree nuts, general/other;

Field Of Science
2020 - Engineering;

Goals / Objectives
The focus of this SBIR project is to develop the FloraPulse µTensiometer for widespread use in crops with small stems. We aim to enable ubiquitous measurement of water potential in commercial, scientific and consumer applications. To this end, we propose to redesign the sensor and installation method for small-stems and field test it in numerous crops.Aim 1: Modify the microchip design to increase response speed and sensitivity (Fig. 4). To achieve ubiquitous use of our probe, we will redesign the microchip to dramatically increase response speed by up to 25x and sensitivity by up to 30x. A faster, more sensitive microchip will enable (1) water potential measurement in annual crops and typical soils that have high (wet) water potential, (2) eventual shrinking of the microchip die, which is currently large and expensive by microfabrication standards, (3) improved long-term sensor accuracy and stability, (4) capture of smaller water potential features the sensor is currently too slow to measure and (5) lower-cost electronics to power and read the microchip.Aim 2: Develop hardware and methods for easy, quick installation in small stems (Figs. 5 - 7). In this aim we will develop an installation method that is 10x faster (1 minute), requires no power tools and produces a wound 25x smaller (3 mm diameter x 7 mm deep) than our current method. These improvements will be tested with an 'artificial stem' developed to test the critical measurement parameters in the laboratory. The improved method will help increase accuracy and customer adoption with our existing (large-stem) crops and enable servicing of numerous crops whether annuals or young perennials.Aim 3: Test critical wound response in numerous small-stem crops. Once the sensor installation method has been developed, the biggest unknown is the wounding response for each plant species. Previous testing has shown a variety of responses: no visible wound response (e.g., apple), phloem-based wounding gels (e.g., prunus), xylem-based clear exudates (e.g., walnut, pecan, avocado) and xylem-based dark exudates (e.g., persimmon). In this aim, Dr. Shackel will undertake a time-series, picture- and microscopy-based study of wounding responses in a variety of crops (kiwifruit, tomato, cotton, corn, melon, beans, coffee) to characterize the feasibility of monitoring water potential in each over long periods. This survey will form the basis of plans for future field testing and implementation of µTensiometers in new crops.Aim 4: Show proof of concept in field crops and improve the design accordingly (Fig. 3). After initial laboratory testing and a wounding response survey, we will validate the installation method in crops we have previously measured successfully (grape and almond), followed by testing in previously unmeasured crops (blueberry, cotton, corn).

Project Methods
Overall, research under this effort will involve multiple methods:Microfabrication of tensiometer chips and new chip prototypes. In particular, we will continue developing the nanoporous Si membrane technology that has enabled our sensor.Continued development and testing of the installation method and hardware for these sensors. New stainless steel installation sleeves will be machined and tested, and the 'mating compound' slurry will continue to be improved to provide better sensor-tissue contact.Improvements and developments on our 'artificial tree' concept for quick testing and iteration on our sensor without the need for field trials. This will be key in continued, quick progress in developing the sensors for this effort, and future ones.Methodical surveys of wounding responses in a variety of crops. The information gathered will be useful to researchers, and in guiding sensor development and market development.Finally, we will work in the field to show that these new versions work reliably in research and commercial contexts.