How to take a water sample- Irrigation Water Analysis

Irrigation Water Analysis

Introduction

High Sodium, excess salinity and high bicarbonates are all big problems when irrigating crops. Knowing the chemistry of your water will help you better manage the water and your soil. The sodium adsorption ratio (SAR) for example, is a critical calculation for assessing the suitability of irrigation water and is based on the relationship between sodium, calcium and magnesium in your water.

Water with a high SAR can quickly degrade soil structure – but this can be avoided, with the use of gypsum and planting crops more resistant to saline waters. In addition to irrigation water analysis we can also perform;

1. Heavy metal analysis 
2. Pesticide residue analysis

if these are identified as potential hazards to your production.

How to take an irrigation water sample

Water samples for irrigation water analysis must be collected in clean bottles, and care must be taken to prevent accidental contamination of the bottle or water sample during sampling and transportation to the water testing laboratory. 

We supply bottles for sampling.  Please email us on support@cropnuts.com to order sample bottles.

Samples should be taken every 6-12 months, depending on the stability of the source water. In general you need to take samples more often from rivers and surface water and less often for borehole water. Below are procedures for Collecting samples from a tap, river, stream, hand or electric pump, borehole and a well.

Equipment 

1. Sample bottles.
2. Water proof marker pen.
3. Labels.

Collecting a sample from a tap

Procedure

1. Remove any external fittings from the tap, such as anti-splash nozzle or rubber tube.
2. Clean carefully the outside nozzle of the tap, especially any dirt/grease which has collected. 
3. Turn the tap on full.
4. Fill the sample bottle from a gentle flow of water, and replace the cap of the bottle.

NB

allow the water to run for a while to clear the pipes. This allows time for the nozzle of the tap to be flushed and any stagnant water in the service pipe  is discharged.

Collecting a sample from a river, stream or other surface water

Procedure

1. Remove the cap and cover of the sample bottle.
2. Face the mouth of the bottle upstream. 
3. Plunge the neck downwards about 30 cm below the water surface.
4. Tilt the neck slightly upwards to let it fill completely.
5. Where there is no current, push the bottle forward horizontally until it is filled.
6. Carefully replace the cap and cover. 

Collecting a sample from a hand/electric pump/borehole

Procedure

1. Continuously operate the pump for at least 5 minutes.
2. Let the water flush the fittings and pipes.  
3. Collect a sample of water by allowing the water from the pump to flow directly into the sample bottle.
4. Carefully replace the bottle cap and cover.

Collecting a sample from a well

Procedure

If the well is one from which water can be raised only by means of a bucket or can,use a  bottle attached to a weight to collect the sample as follows:

1. Tie a sterile sample bottle onto a length of rope or strong string. 
2. Use a stone or weight, and attach the bottle just above the weight.
3. Remove the cap from the bottle, and lower the bottle into the well to a depth of about 1 meter. 
4. When no more air bubbles rise to the surface, raise the bottle out of the well and replace the cap.

The quality of any analysis is directly related to how well the sample is collected.

Irrigation and Water Analysis Packages

For more information please contact us through:

Crop Nutrition Laboratory Services Ltd.

Off Limuru Road, Limuru, Kenya

Telephone +254 (0) 711094444, + 254 (0) 720 839 933

Email support@cropnuts.com