Contents

Farming & Agriscience Industry
The Practical Guide to Surface Science (2026)

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Written by
Dr Amit Pratap Singh
PhD, Delhi University Post Doc - AIST Japan
Guest Author
Read More
alidad
Reviewed by
Dr Alidad Amirfazli
Dr. Amirfazli, a leading expert in surface wetting and superhydrophobic coatings, has 250+ publications, edits Advances in Colloid and Interface Science, and has received multiple research awards.
Scientific Advisor & Co-founder
Read More
D54c15105cfe94f786c500e4091d6ea65457608fde49ba183c8f862814a54249?s=100&d=m
Written By

Dr Amit Pratap Singh

Guest Author

PhD, Delhi University

Post Doc - AIST Japan

alidad
Reviewed By

Dr Alidad Amirfazli

Scientific Advisor & Co-founder

Dr. Amirfazli, a leading expert in surface wetting and superhydrophobic coatings, has 250+ publications, edits Advances in Colloid and Interface Science, and has received multiple research awards.

Featured Studies & Publications

Research Paper Contact angle measurement with a smartphone
Research Paper Surface tension measurement with a smartphone using a pendant drop

This is a practical guide to Surface Science for researchers working in the Farming & Agriscience Industry.

In this all-new guide you’ll learn all about:

  • Crucial surface science principles
  • The significance of surface science measurements for the Farming & Agriscience industry
  • Applicable ASTM Standards & Guidelines

Let’s dive right in.

Farming & Agriscience

Contents

measurement

Contact Angle Measurement

tension

Surface Tension Measurement

energy

Surface Energy Measurement

sliding angle

Sliding Angle Measurement

realworld

Real World Applications

standardand guide

Standards and Guidelines

Executive Summary

What it covers: How agriscience labs use contact angle, surface tension, surface free energy and sliding angle on leaves, soil, sprays, coatings and films. Each measurement is tied to a field or lab problem and to a published client study or case study.
Key insights: Leaves and soil are rough, so the fitting method matters as much as the instrument. A University of Toronto study measured water contact angles of 139.7 to 150.1 degrees on regrown aspen leaves. At Murdoch University, tight cropping and a tilted baseline fixed analysis errors on real soil.
Business value: Wetting checks screen adjuvants, coatings and soil treatments on the bench before slow field or shelf life trials. One portable kit covers four measurements, so a small research team can run them without booking a shared lab instrument.
Standards to follow: ASTM D1331 describes surface and interfacial tension of surfactant solutions by the ring and plate methods. The Dropometer uses the pendant drop method, so treat its result as an alternative value and do not label it D1331. We found no ISO or ASTM standard for contact angle on soil.
Bottom line: Measure surface tension while you formulate a spray or coating, and contact angle once it meets a leaf, peel or soil. Start with the measurement that matches your problem, then book a 15 minute demo to try it on your own samples.

Chapter 1: Introduction

In farming and agriscience, many costly losses start where a liquid meets a surface. A spray that beads on a waxy leaf runs off before it works. Rain that sits on water repellent soil never reaches the roots.

These are the places where wetting decides yield in agriscience work:

The Dropometer contact angle and surface tension kit measures contact angle, surface and interfacial tension, surface free energy and sliding angle with one portable setup. Its method was validated against a KRUSS DSA100E in two peer reviewed papers. If you are new to the terms, start with wettability.

We use the following surface properties to understand the behavior of Farming & Agriscience products and improve their quality.

Chapter 2: Contact Angle Measurement

The contact angle quantifies the wettability of a surface by representing the angle between a liquid’s surface and a solid surface.
Dropletlab Research

Sample Image taken from Droplet Lab Tensiometer.

Young – Laplace Method

  • 1. This method uses the whole drop profile to calculate the contact angle value.
  • 2. This method is only compatible with an axisymmetric drop, which is not always seen in practice because a needle is typically inserted into the drop to increase or decrease the drop volume.
  • 3. This method yields more consistent results than the polynomial fitting method.

Polynomial Method

  • 1. This method uses only a portion of the drop profile to calculate the contact angle value.
  • 2. This method is compatible with both axisymmetric and non-axisymmetric drops.
  • 3. The measurement results of this method are less consistent, as they can be influenced by local surface imperfections.
Dynamic Contact Angle

Ideally, when we place a drop on a solid surface, a unique angle exists between the liquid and the solid surface. We can calculate the value of this ideal contact angle (the so-called Young’s contact angle) using Young’s equation. In practice, due to surface geometry, roughness, heterogeneity, contamination, and deformation, the contact angle value on a surface is not necessarily a single consistent value but rather falls within a range. The upper and lower limits of this range are known as the advancing and receding contact angles, respectively. The values of advancing and receding contact angles for a solid surface are highly sensitive to many parameters, such as temperature, humidity, homogeneity, and minor contamination of the surface and liquid. For example, the advancing and receding contact angles of a surface can differ at different locations.

Dynamic Contact Angle versus Static Contact Angle

Practical surfaces and coatings naturally show contact angle hysteresis, indicating a range of equilibrium values. When we measure static contact angles, we get a single value within this range. Solely relying on static measurements poses problems, like poor repeatability and incomplete surface assessment regarding adhesion, cleanliness, roughness, and homogeneity.

In practical applications, we need to understand how easily a liquid spreads (advancing angle) and how easily it is removed (receding angle), such as in painting and cleaning. Measuring advancing and receding angles offers a holistic view of liquid-solid interaction, unlike static measurements, which yield an arbitrary value within the range.

This insight is crucial for real-world surfaces with variations, roughness, and dynamics, aiding industries like cosmetics, materials science, and biotechnology in designing effective surfaces and optimizing processes.

Learn how Contact Angle measurement is done on our Tensiometer

For a more complete understanding of Contact Angle measurement, read our Contact Angle measurement: The Definitive Guide

Contact Angle measurement: The Definitive Guide

Open Benchmark Data: Contact Angle & Surface Energy

These reference measurements show how deionized water wets four standard substrates measured with the Droplet Lab Dropometer. Use them as visual and numerical benchmarks when you're checking your own sample preparation, treatments, and chemistry.

Full contact angle and surface energy datasets (including additional liquids and statistics) are available on our dataset hub.

Glass - DI Water
Glass - DI Water
Nylon - DI Water
Nylon - DI Water
PMMA - DI Water
PMMA - DI Water
Teflon - DI Water
Teflon - DI Water

The droplet images above are taken from the same benchmark series as our open dataset. For each substrate and probe liquid we report:

● Advancing and receding contact angles (and hysteresis)
● Derived surface energy (SFE) values based on multi-liquid measurements
● Measurement conditions, uncertainties, and sample preparation details

Comparing your own droplet shapes and angles against these references is a fast way to spot contamination, treatment drift, or unexpected changes in wettability.

Explore the full benchmark datasets (contact angle + surface energy)

Measurements were performed with the Droplet Lab Dropometer under controlled laboratory conditions. Treat these values as sanity checks and starting points for your own process targets, not as product specifications.

Chapter 3: Surface Tension Measurement

This property measures the force that acts on the surface of a liquid, aiming to minimize its surface area.

Surface Tension Measurement

Sample Image taken from Droplet Lab Tensiometer

Dynamic Surface Tension

Dynamic surface tension differs from static surface tension, which refers to the surface energy per unit area (or force acting per unit length along the edge of a liquid surface).

Static surface tension characterizes the equilibrium state of the liquid interface, while dynamic surface tension accounts for the kinetics of changes at the interface. These changes could involve the presence of surfactants, additives, or variations in temperature, pressure, and composition at the interface.

When to use Dynamic Surface Tension Measurement

Dynamic surface tension is essential for processes that involve rapid changes at the liquid-gas or liquid-liquid interface, such as droplet and bubble formation, coalescence (change in surface area), the behavior of foams, and the drying of paints (change in composition, e.g., evaporation of solvent). It is measured by analyzing the shape of a hanging droplet over time.

Dynamic surface tension applies to various industries, including cosmetics, coatings, pharmaceuticals, paint, food and beverage, and industrial processes, where understanding and controlling the behavior of liquid interfaces is essential for product quality and process efficiency.

Learn how Surface Tension measurement is done on our Tensiometer

For a more complete understanding of Surface Energy measurement, read our Surface Tension measurement: The Definitive Guide

Surface Tension measurement: The Definitive Guide

Chapter 4: Surface Energy Measurement

Surface energy refers to the energy required to create a unit area of a new surface.
231

Sample Image taken from Droplet Lab Tensiometer

Learn how Surface Energy measurement is done on our Tensiometer

For a more complete understanding of Surface Energy measurement, read our Surface Energy measurement: The Definitive Guide

Surface Energy measurement: The Definitive Guide

For benchmark contact angle and surface energy values on glass, nylon, PMMA, and Teflon, see the Open Benchmark Data panel above or visit our Dataset Hub for full CSV downloads.

Dataset Hub

Chapter 5: Sliding Angle Measurement

The sliding angle measures the angle at which a liquid film slides over a solid surface. It is commonly employed to assess the slip resistance of a surface.

sliding angle 1

Sample Image taken from Droplet Lab Tensiometer

Learn how Sliding Angle measurement is done on our Tensiometer

For a more complete understanding of Sliding Angle measurement, read our Sliding Angle Measurement: The Definitive Guide

Sliding Angle Measurement: The Definitive Guide

Chapter 6: Real-World Applications

Within the Farming & Agriscience industry, several case studies exemplify the advantages of conducting surface property measurements.

Superhydrophobicity Mechanism of Refoliated Quaking Aspen Leaves After Complete Defoliation by LDD (Gypsy, Spongy) Moth Caterpillars

The paper investigates a severe mid-summer defoliation event (Ontario, Canada, 2021) where quaking aspen trees were completely stripped of leaves by LDD moth caterpillars, then refoliated within the same year. The regrown leaves were smaller, but still exhibited strong non-wetting behavior. The authors attribute the high water contact angles to a hierarchical “dual-scale” leaf surface: nanoscale epicuticular wax (ECW) crystals superimposed on microscale papillae, consistent with a Cassie-Baxter non-wetting state. Differences between refoliated vs. typical-season leaf surface morphology are discussed in relation to environmental growth conditions (notably seasonal temperature during development after budbreak).

Role of Droplet Lab Goniometer

The Droplet Lab Dropometer was used to quantify the wettability recovery of refoliated aspen leaves by measuring water contact angle (WCA) on the adaxial (upper) leaf surface during the regrowth period. Specifically:

  • In Section 2.3 (“Wetting characteristics”), the study describes WCA measurements performed with the Droplet Lab Dropometer using 10 µL deionized water droplets, with ≥9 measurements per sampling date and reporting mean ± standard deviation.
  • These WCA measurements provided the primary functional metric linking:
    (1) refoliation timing and leaf development, to
    (2) micro/nano surface morphology (SEM), and to
    (3) the onset and persistence of a superhydrophobic/non-wetting state.

Where contact angle is explicitly described in the paper:

  • Methods: Section 2.3 (Droplet Lab Dropometer, 10 µL DI water, replicate counts)

Results: Section 3.2, plus Fig. 2-4 and Table 1 (WCA values/trends and correlation to surface structures)

Key Findings

  • Same-season recovery is possible: Quaking aspen in the study could refoliate in the same year after complete LDD defoliation, though with smaller leaves than typical spring growth.
  • High hydrophobicity appears quickly: Refoliated leaves were already strongly hydrophobic within ~2 days after budbreak, rather than requiring a long “ramp-up” period.
  • Measured WCA range during refoliation: Reported average WCAs across the refoliation study window were approximately ~140° to ~150° (with date-to-date variation reported as mean ± SD). (See Section 3.2, Fig. 2-4, and Table 1.)
  • Mechanism confirmed by structure + WCA: SEM showed a dual-scale hierarchy (microscale papillae + nanoscale ECW crystals) consistent with a Cassie-Baxter non-wetting state, aligning with the high WCA measurements.
  • Ultra-low adhesion prevented roll-off testing: The team notes they could not accurately measure roll-off angle because droplets rolled off immediately with slight disturbance (stated in Section 2.3).
  • Environmental conditions likely tune morphology: The refoliated leaves showed subtle morphology differences versus normal-season leaves, plausibly linked to temperature during growth after budbreak.

Why It Matters

For forestry, tree health monitoring, and agriscience, this paper shows that contact angle can serve as a fast, quantitative “functional recovery” metric after insect-driven defoliation events. In practical terms, pairing WCA with microscopy allows researchers and land managers to distinguish between “leaf return” and return of critical surface function (water shedding/non-wetting), which can influence canopy water interception, surface cleanliness/pathogen interactions, and broader ecohydrology behaviors discussed by the authors.

Method Snapshot

  • Sample: Refoliated quaking aspen (Populus tremuloides) leaves collected repeatedly during July-Aug 2021 after complete defoliation.
  • Droplet: 10 µL deionized water dispensed on the adaxial leaf surface.
  • Angle type: Static water contact angle (WCA) (advancing/receding not reported).
  • Temperature: Not explicitly specified for the contact angle test conditions (study provides outdoor weather context for growth conditions).
  • Surface tension: Not measured/reported (DI water used as the probe liquid).

Data Note

Comparison of average WCAs (with standard deviations) on the adaxial surface of quaking aspen leaves from the refoliation period in 2021 (current study, July 18th -August 26th, 2021) and from the same period in a year for a normal growth season (July 18th - September 1st, 2012) (Tranquada and Erb, 2014). Averages are based on at least 9 contact angle measurements per leaf collection date. 

Figure

Citation (APA Format)

Sui, X., Tam, J., Keller, H., Liang, W., & Erb, U. (2023). Superhydrophobicity mechanism of refoliated quaking aspen leaves after complete defoliation by LDD (gypsy, spongy) moth caterpillars. Plant Science, 330, 111659. https://doi.org/10.1016/j.plantsci.2023.111659

View Publication →

Pesticide retention on leaves

A spray only works if it stays on the leaf. Contact angle of a spray drop on the leaf shows whether it spreads into a film or beads up, and beaded drops are more likely to bounce or run off.

Some leaves are extremely water repellent. A University of Toronto study measured water contact angles of 139.7 to 150.1 degrees on regrown quaking aspen leaves. The University of Toronto group notes the drops rolled off at the slightest tilt. Our leaf coverage use case sets out a test plan for spray retention.

Pesticide retention on leaves

Spray formulation for pest control

Surface tension of a tank mix affects how drops form at the nozzle and how they spread on the target. Pendant drop surface tension gives a quick batch check on adjuvant dose. A dilution series shows where adding more surfactant stops lowering surface tension.

Nozzles create new surface in milliseconds, faster than a pendant drop can follow, so treat the reading as a formulation screen and not a field prediction. Our page on drift reduction and adjuvant selection explains how surface tension fits beside droplet sizing. See also surfactant.

Spray formulation for pest control

Soil moisture and water repellent soil

Water repellent soil stops rain and irrigation water from soaking in. Water drop penetration time classes how long the repellency lasts. Contact angle on soil particles adds a direct reading of how well the soil wets.

A Murdoch University research group in Western Australia uses the Dropometer on treated and untreated soil. Rough soil at first gave calculation errors. After tight cropping and a tilted baseline, a test image returned left and right angles of 37 and 35 degrees. Our soil amendment use case lists the steps and the limits.

Soil moisture and water repellent soil

Seed coatings and water uptake

A seed coating has to let water through to the seed. Water contact angle on the coated surface, read over the first seconds, shows how fast the coating wets and starts to take up water.

The same time series method is used on bio based films made from crop residues. Researchers tracked water contact angle on alfalfa lignocellulosic films, where it fell from 78.9 degrees at 0 seconds to 54.5 degrees at 30 seconds. A study of wheat straw cellulose film fitted a similar decline to a wetting rate. See dynamic contact angles.

Seed coatings and water uptake

Irrigation water and infiltration

Wetting agents added to irrigation water lower its surface tension so it spreads and soaks into soil more evenly. Pendant drop surface tension checks the wetting agent dose. Contact angle on the soil shows the effect where the water lands.

Measure at a known temperature, since surface tension changes with temperature. Our surface tension measurement guide explains the pendant drop method. For runoff and water quality work, a Clemson group used contact angle to choose coatings for a dip and read orthophosphate sensor.

Irrigation water and infiltration

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If you are interested in implementing these or any other applications, please contact us.

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Chapter 7: Standards and Guidelines

In an industry where precision reigns supreme, how can Farming & Agriscience manufacturers ensure their products withstand scrutiny? The answer lies in standards and guidelines: the compass that guides them through the complex maze of quality and performance.

ASTM D1331, Surface & Interfacial Tension of Solutions (Du Noüy Ring / Wilhelmy Plate Force Methods)

What it is

ASTM D1331 is a method-defined standard for measuring surface tension and interfacial tension of liquid materials using force tensiometry, where a Du Noüy ring or Wilhelmy plate is pulled from a liquid or across a liquid-liquid interface. Results should only be labeled “ASTM D1331” when produced using these ring/plate force methods (optical pendant-drop methods are not D1331 as-written).

When to use it

Formulation QC and supplier/customer specs for agrochemicals/adjuvants

Use when a product spec, COA language, or dispute-resolution test requires a ring/plate surface or interfacial tension value reported as ASTM D1331 (e.g., spray adjuvants, EC/ME concentrates, tank-mix additives).

R&D screening tied to spray performance and emulsion behavior

Use when optimizing wetting/spreading on leaves, coverage, compatibility, and emulsification (water/oil) where tension is a sensitive indicator of surfactant package changes or contamination.

In-scope / Out-of-scope

In scope
  • Surface tension of agriculture-relevant liquids (e.g., adjuvant concentrates, surfactant solutions, pesticide dilutions, fertilizer solutions, spray tank mixes) measured by Du Noüy ring or Wilhelmy plate.
  • Interfacial tension for systems with two liquid phases (e.g., water/oil or water/solvent) to support emulsion design, compatibility, and phase-separation troubleshooting.
  • Batch-to-batch trending when temperature, sample handling, and ring/plate cleanliness are controlled and documented.
  • Comparative studies across surfactant packages (nonionic/anionic, organosilicone, etc.) using consistent geometry and procedures.
Out of scope
  • Optical pendant-drop (Young-Laplace) measurements (e.g., Dropometer pendant drop) and other non-force optical methods, these are not ASTM D1331 compliant as-written.
  • Dynamic surface tension at short timescales relevant to spray atomization (may require other methods if you need milliseconds-to-seconds behavior).
  • Highly particulate, dirty, or solid-laden samples (e.g., suspensions/SCs, some biological slurries) where ring/plate wetting/contamination makes results unreliable without a validated sample-prep approach.
  • Leaf contact angle/retention on plant surfaces (use contact-angle/leaf-wetting protocols; D1331 measures liquid tension, not surface wetting on solids).

Minimum you must report (checklist)

  • Sample identity (product/formulation name, lot/batch; dilution rate and water quality if a tank-mix simulation is used, hardness, pH, ions).
  • Property measured (surface tension or interfacial tension; for interfacial, clearly identify both phases and their preparation).
  • Instrument + geometry (Du Noüy ring or Wilhelmy plate; material and relevant dimensions).
  • Temperature and equilibration time (setpoint/measured temperature; time since mixing/dilution, critical for surfactants).
  • Sample preparation and handling (mixing method, degassing/settling, filtration if used; bubble/foam controls).
  • Cleaning/conditioning protocol for ring/plate and vessels (including how you verify cleanliness with a reference check).
  • Replicates and statistics (n, mean/median, SD/IQR; outlier/rejection rule).
  • Any deviations from ASTM D1331 or your internal SOP (and why).

Note: Dropometer (optical pendant-drop Young-Laplace) can be a strong internal screening/trending tool for spray-mixture drift and contamination, but it must not be reported as “ASTM D1331” because it does not use ring/plate force tensiometry. If you want D1331-equivalent decision gates from a faster method, build and maintain a documented method-bridging correlation to a D1331 ring/plate reference.

How to interpret results (guardrails)

  • Method-specific means method-specific: do not assume pendant-drop γ equals D1331 γ without a validated correlation and ongoing verification.
  • Tie interpretation to the use case: lower surface/interfacial tension often supports wetting/emulsification, but real spray outcomes also depend on viscosity, formulation elasticity, droplet size distribution, and plant surface chemistry, validate against field/bench performance tests.
  • Use variability as a warning signal: rising scatter or unstable readings often indicate contamination (oils/silicones), foam/bubbles, poor cleaning, or phase instability, fix the cause before making formulation decisions.
  • Standardize “tank-mix realism”: if you’re testing diluted sprays, lock down water source/condition (hardness, pH), dilution order, and wait time, or you’ll measure process variation instead of formulation change.
Read our ASTM D1331 page View the official ASTM D1331 Standard

Now It’s Your Turn

We hope this guide showed you how to apply surface science in the Farming & Agriscience industry.

Now we’d like to turn it over to you: 

  • What’s the #1 real-world application from this post that you want to try first?
  • Perhaps we missed a relevant industry standard.
  • Or maybe you have a question about something you read.

Feel free to leave a comment below—we’d love to hear from you.

Frequently asked questions

Which surface measurement should an agriscience lab start with?

Start with the problem you need to solve. Use surface tension for spray tank mixes, adjuvants and coating liquids. Use contact angle on leaves, peels, seeds and soil to see whether a liquid wets them. Add surface free energy when you compare coatings on produce, and sliding angle for very water repellent leaves. Our contact angle guide explains each step.

How do you measure contact angle on a leaf?

Cut a flat section of leaf and fix it to a slide or coupon with double sided tape. Place a small water drop and read the angle at a set time. In the aspen leaf study, researchers used 10 microlitre drops and took at least nine readings per sample. Very repellent leaves may not hold a drop on any tilt, so sliding angle cannot always be measured.

Can the Dropometer measure contact angle on soil?

Yes, with care over image handling. Soil particles are fixed to double sided tape and a small drop is read early, before it soaks in. The Murdoch University case study shows how a tilted baseline, tight cropping and polynomial fitting solved errors on rough soil. Our soil wetting use case explains how to pair the result with water drop penetration time.

How do I find the surface free energy of a fruit peel?

Measure contact angles of two or more probe liquids with known properties on the peel, then work out surface free energy with our contact angle to surface energy calculator. The Research Institute for Bioscience and Biotechnology in Nepal used this approach on tomato skin to compare edible coatings. Dr Alidad Amirfazli advised them to choose probe liquids that give angles ideally above 30 degrees.

Which standards apply to surface tension and wetting in agriculture?

ASTM D1331 describes surface and interfacial tension of surfactant solutions with a ring or plate. The Dropometer uses the pendant drop method, which gives an alternative value, so do not report it as D1331. For soil, we found no ISO or ASTM contact angle standard; drop penetration time classes are used instead. Our edible coatings page follows the ISO 19403-2 approach for peel surface free energy.

How accurate is the Dropometer?

The drop shape method was validated against a KRUSS DSA100E in two peer reviewed papers, one in Review of Scientific Instruments and one in Colloids and Surfaces A. Published contact angle accuracy is 0.35 degrees. On rough leaves and soil, the fitting method matters, so record which fit you used. See our validation papers.

Do published agriculture and food studies use the Dropometer?

Yes. Researchers have used it on packaging films made from crop residues, including corncob films for raspberries and alfalfa and carrageenan films. The Clemson McLamore lab uses it on graphene sensor electrodes, including an aptasensor for apple stem pitting virus. Browse every study on our client citations page.

Standards, evidence and resources

1. Use cases Case studies Client citations (our analysis of each paper) Use case collections Further resources