“The raw-water EC is high. Should we buy RO?” is a common question in water preparation for soilless cultivation. EC provides information related to soluble salts, but does not describe the full ionic composition on its own. It certainly cannot directly prescribe treatment for blueberries, roses, or all crops. Organize the raw-water report and growing objectives first, then compare water-treatment options.
Distinguish three sampling locations
Raw water identifies the conditions entering the system; treated water checks the treatment task; nutrient solution supports growing management. Record the location, time, temperature, and instrument units. Readings from different locations cannot simply be combined as the same indicator. “Raw-water EC” is not the EC of the nutrient solution after fertilizer has been added.
| Item | What it helps explain | What it cannot establish on its own |
|---|---|---|
| EC / electrical conductivity | Conditions related to soluble salts in the water; specify the units and temperature conditions | Does not directly indicate the concentration of each ion or suitability for a crop |
| pH | The water's acidity or basicity | Is not alkalinity and cannot alone represent buffering capacity |
| Alkalinity | The water's ability to neutralize acid; relevant to assessments of water preparation and growing-media management | Cannot be replaced by assessing whether pH is high or low |
| Calcium, magnesium, sodium, chloride, and other constituents | Identify relevant constituents in relation to the intended use | Do not infer individual ion concentrations from a single total value |
| Turbidity, sediment, and relevant contaminants | Determine testing, filtration, and management tasks using the water source and intended use | Clear water does not mean it is free of contamination or suitable for every use |
Determine the treatment task before discussing equipment
For sediment in surface water, filtration and upstream management can be assessed first. Dissolved-salt or specific-ion issues require corresponding testing and treatment assessment. RO, ultrafiltration, and softening perform different tasks and cannot be grouped under one generic “purification” label. Hardness and total-salt tasks also need separate confirmation. The growing team should provide the crop, cultivation method, fertilizer, and circulation conditions so that the water-treatment team can discuss the process and supply scope accordingly.
Why pH and alkalinity cannot be used interchangeably
The two tests provide different information. Adjusting pH to a particular reading does not establish that all raw-water issues have been resolved. This material does not provide a universal acid dose or nutrient formulation. Specific adjustments must be determined by the relevant technical personnel using test results, material compatibility, instructions for use, and site safety conditions.
A raw-water file that supports clear communication
Retain the water source, sampling location, date, testing organization, test items, units, and complete report. Record well water, surface water, and tap water separately, and recheck when the source changes or a significant change occurs. When placing historical reports alongside current readings, state whether they are comparable. Do not directly apply recommended ranges from overseas greenhouse information as acceptance values for specific crops in Yunnan.
Frequently asked questions
Is there one universal EC limit for blueberry irrigation water?This material sets no uniform threshold. The cultivar, growing medium, fertilizer, drainage, and specific growing plan must be considered together.
Does high raw-water EC always require RO?Check the ions, growing objectives, and available water sources. A single reading cannot determine the decision.
Can the original fertilizer-mixing plan still be used directly after water treatment?Treatment may change the constituents. Growing personnel should recheck water preparation and nutrient management.
Supporting records you can fill in
Further reading
- Water solutions for soilless cultivation
- Where to record blueberry water-use information
- Differences between ultrafiltration and RO tasks
- Knowledge & resources
- Submit the water requirements for this inquiry
Sources and scope of application
Gudian Technology compiled this material using public technical information and purchasing discussion needs, with AI-assisted drafting. Content checked on October 6, 2026. The sources below explain general principles. They are not test reports, authorizations, or evidence of project results for this site's equipment models. Confirm the specific equipment configuration, expenses, services, and acceptance criteria for the intended use through written documents.
- Penn State Extension：Interpreting Irrigation Water Tests
- FAO: Water Quality for Agriculture, the relationship between water quality and specific uses
Align testing locations before discussing whether raw-water EC needs to be reduced
Raw water, treated water for preparation, nutrient solution with fertilizer already added, and return solution are four different subjects of observation. Comparing their readings directly may misinterpret normal changes caused by fertilizer mixing as an equipment problem. Raw-water EC reflects the combined electrical conductivity of soluble salts. It does not directly identify which ions exceed a particular crop's management targets.
| Location | Details to specify | Questions to answer |
|---|---|---|
| Raw-water sampling point | Water source, date, EC units, temperature, and test method | Are the report's sodium, chloride, calcium, magnesium, alkalinity, and other results sufficient to explain the issue? |
| Treated water for preparation | Records for the relevant treatment equipment and the same batch of water | Were conditions comparable before and after treatment? |
| Nutrient solution | Formulation version, fertilizer addition status, and sampling point | Do the growing team's targets correspond to the current stage? |
| Return solution or drainage solution | Collection location, whether solutions were mixed, and management records | Its readings cannot be treated directly as raw-water treatment requirements |
Standardize units and retain the original readings
Record both the EC value and its unit: 1 mS/cm equals 1000 μS/cm. Also record whether the instrument uses temperature compensation. pH and alkalinity do not represent the same property. If total hardness is reported as CaCO₃, copy the report's measurement basis exactly. A converted reading from a TDS meter cannot replace ion testing or hardness measurement.
To decide whether to use RO, check the raw-water composition, available sources, downstream growing plan, and water demand together. This article does not provide a universal nutrient-solution formulation or directly apply overseas greenhouse ranges as acceptable thresholds for all crops in Yunnan.
Sources and scope
Drafted with AI assistance on 8 October 2026 and checked item by item against the knowledge base and the public sources below. Manufacturer information explains the relevant technology; it does not imply that Gudian is an authorized distributor or manufacturer for that brand. Equipment specifications are subject to the selected model and confirmed documents.
Scope of farmland irrigation standards and nutrient management
Checked on 9 October 2026: GB 5084—2021, Standard for Irrigation Water Quality, took effect on 1 July 2021 and covers farmland irrigation water within its specified scope. It is not a nutrient-solution formula for soilless cultivation. A value in the standard cannot be applied as a universal target for every crop, substrate and growth stage. The existing four sampling points, unit explanations and downloadable sheets remain. Also identify this project’s use requirements and the person responsible for confirming their applicability.
- Check drinking-water, industrial-production and farmland-irrigation requirements separately. A generic claim that water is purified does not cover every use.
- Confirm the source, blending and disposal arrangements for reused water separately. RO or filtration alone does not establish its suitability for irrigation.
- The growing team confirms water preparation and agronomic requirements; the water-treatment team checks equipment and water-supply handover. Leave unconfirmed items pending review.
- GB 5084—2021: Standard for Irrigation Water Quality; Defines tasks within its water-quality scope; not product certification or a promise of growing results. Existing university references explain general principles, without directly transferring overseas thresholds.