Runoff, Pour-Through, Slurry, and Tissue Testing
Select, standardize, and interpret root-zone and plant tests without comparing values generated by incompatible methods.
Educational reference · evidence, sources, and limits shown below
Select, standardize, and interpret root-zone and plant tests without comparing values generated by incompatible methods.
Terms to know
- Runoff
- Drainage produced during irrigation; its composition depends on flow path, timing, volume, and container state.
- Pour-through
- Standardized displacement method that collects substrate pore solution after controlled pre-irrigation and timing.
- Slurry or dilution extract
- Substrate mixed with a defined water ratio for pH or EC measurement.
- Tissue analysis
- Laboratory measurement of elemental concentration in a defined plant organ sampled by a controlled protocol.
Core science
Every testing method samples a different fraction. Casual runoff is convenient but strongly affected by irrigation volume, dryback, preferential flow, and container geometry. Standardized pour-through estimates pore-water conditions with minimal root disturbance. Slurry, 1:2 dilution, saturated-media extract, and squeeze methods use different dilution and extraction conditions.
Method-specific reference ranges cannot be exchanged. An EC from a 1:2 extract is expected to differ from a pour-through or saturated-media extract from the same container. Trend value depends on repeating sample timing, water volume, plant size, container, instrument, and procedure.
Tissue analysis integrates acquisition and growth but is sensitive to organ, node, age, contamination, washing, stage, time, cultivar, and laboratory method. A high tissue concentration can reflect luxury uptake or slow growth; a low concentration can reflect dilution by rapid growth. Pair tissue with input, root zone, growth, and symptom evidence.
Why this matters in cultivation
- Choose one routine root-zone method appropriate to the substrate and container, train operators, and build method-specific control limits from healthy crops.
- Use laboratory tissue and solution testing when routine indicators disagree, when a micronutrient or contaminant is involved, or when a corrective action could create substantial risk.
Measure and record
Sampling plan
Population, randomization, cultivar, stage, container, root zone, tissue organ, and replicate count.
Root-zone method
Pre-irrigation, wait time, collection volume, dilution ratio, water quality, temperature, and extraction time.
Tissue method
Node or organ, age, number of plants, washing, handling, laboratory, digestion, and reporting units.
Chain of custody
Sample ID, collector, time, container, preservation, shipment, receipt, and deviations.
Interpretation
Method-specific reference, healthy control, paired pH/EC/ions, uncertainty, action, and re-sample date.
Common misconceptions
Correction: It is a mixed drainage sample shaped by irrigation and flow path.
Correction: Different extraction ratios and solution fractions produce systematically different readings.
Correction: Supply, growth dilution, roots, pH, environment, sampling, and interactions still require review.
Evidence limits
Validated cannabis tissue sufficiency ranges are limited and laboratory methods vary. Internal healthy-crop baselines and consistent procedures are often more defensible than generic charts.
Related encyclopedia topics
- THC-ENC-052, THC-ENC-087-090, THC-ENC-131-140, THC-ENC-327-328, and THC-GROW-080.
Source notes
- LeBude A.V. and Bilderback T.E. The Pour-Through Extraction Procedure: A Nutrient Management Tool for Nursery Crops. NC State Extension.
- Cox D.A. How to Use pH and EC Pens to Monitor Greenhouse Crop Nutrition. University of Massachusetts Extension.
- Cox D.A. Soluble Salts and Electrical Conductivity for Greenhouse Crops. University of Massachusetts Extension.
- Cockson P. et al. (2022). Visual Symptoms of Nitrogen, Phosphorus, Potassium, and Magnesium Deficiency in Hemp. e-GRO Edible Alert 8.11.
This lesson summarizes the source material and its evidence limits for education. Use direct measurement, controlled comparison, and the cited sources when conditions differ or a decision carries meaningful risk.