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Water, salt and cows in pastures

Let’s use disaster as a chance to learn more about measuring the salt content in water

The recent loss of 200 head of stock due to bad water brings the subject of water and cows into sharp focus. The loss occurred at a pasture near Shamrock, Sask., about 75 km southwest of Moose Jaw. Let me first offer condolences to the producers who lost cattle. In my experience cows are more than just money to stock growers.

This piece is not about placing blame on anyone, but hopefully will lead to some very simple procedures that will prevent such loss in the future.

Measuring salt content of water in the field

The salt content of water can be very easily measured in the field with sufficient accuracy to be very useful to solve many problems.

Salts carry an electric charge. The more salts in a body of water the more electric current it will carry. We measure that as the EC (Electrical Conductivity). The higher the EC, the higher the salt content of the water. For more detail those who have Henry’s Handbook of Soil and Water can check out Chapter 9.

EC is reported in MicroSiemens per centimetre (µS/cm). EC is temperature dependent so all readings are corrected to a standard 25 C. For many of our waters, EC is a good first approximation of the Total Dissolved Solids in parts per million (ppm).

As a first approximation, interpretation of EC (µS/cm) for cows is as follows:

EC < 1,000 µS/cm: Good to go. But water that good is rare in some areas.

EC 1,000 to 5,000 µS/cm : Problems increase and there may be poor production even if there is no actual serious distress. By 5,000 µS/cm, you should be looking for a better water source.

EC 10,000+ µS/cm: Forget it. Find another source.

Note: Barry Blakley of the Veterinary College, University of Saskatchewan assisted with the general guidelines regarding EC and cows. I have more than a passing acquaintance with Prairie surface and ground waters but know little about cattle. Thanks Barry!

Near my Dundurn farm, 2001

The turn of the century was near the end of a long dry cycle that led to very low surface water levels. In general, as water levels decline the salt level rises.

On a quarter section very near me a neighbour noticed cows in distress, alerted the owner, and the cows were immediately moved off. Veterinary assistance established that very high sulphate levels were the culprit. I measured the water at that location on October 2, 2001 and found the EC = 14,750 uS/cm. I keep EC Meter and probe in a small briefcase along with notebook for an ongoing record.

In 2001, my good neighbours, the Janzens, were digging backhoe tests to find a site for a trackhoe dugout. I used my trusty EC meter to help. A shallow clean sand produced very clean looking water but the salt level was nearly as high as that where the neighbour’s cows were in trouble. Another location was chosen with water not as clean but with lower salt.

In 2015 Janzens acquired SE 27 32 3W3, after 10 wet years and several large snowpacks. As they suspected, the water was now diluted to safe levels. But, notice that after part of a dry summer (2017) the salt levels have risen. What is OK one time may not be later.

In the famous northeast swale that is much in Saskatoon news, cattle deaths from bad water also occurred around 2001.

This is a slough beside my buildings on NW 22 32 3W3. The photo was taken in 2013. The water level was about that high for years but is now falling fast with the low 2017 rain and very little snow last winter.
photo: Les Henry

Keeping an EC meter honest

Of course lab analysis will still be needed to get a complete water test and make sure the answer is correct. Some veterinarians now carry an EC meter so they can do a spot test. I have carried an EC meter since we started the soil salinity work in 1982 and now have several notebooks full of data from all over the prairies, and even the mountains (not much salt there). Chapters 8 and 9 of Henry’s Handbook of Soil and Water includes a selection of that data.

To keep my meter honest I use our Saskatoon tap water. If I get a different number a check with the City water treatment lab sorts it out. A drilled well would work as a check for most pastures. Deep wells (>75 feet) normally do not change much.

Slough water is not always less salty

In a wet cycle, slough water is not always less salty.

On my Dundurn farm I’ve monitored three sloughs for about 10 years. One slough is shown here. It was dry at the turn of the century and was hayed by a neighbour for a few years. The dry cycle lowered the pressure in all aquifers as well as drained all the sloughs.

The big snow melt of 2005 was the start of our wet cycle.

When the wet cycle started the water was fairly good. As the water level rose to cover the salt ring it dissolved many salts. As well, aquifer pressures would be up, adding groundwater to the picture. By 2013 the EC was at 3,350 µS/cm, 2014 =3,500, 2015=3,850 and 2017=5,000. The water level has dropped very noticeably this summer and concentration by evaporation is now taking place. At this level a stock grower should be looking for another source.

Visual inspection is a poor guide

Looking at surface water tells you almost nothing about salts. In fact, very salty water is usually very clear and looks great. It is so salty that algae will not grow, or anything else.

Vegetation can be a clue. Cattails only grow up to about EC=3,000 µS/cm. The presence of a surface scum of algae that might include bad blue-green algae, usually indicates water that is not very high in salt.

Visual inspection may be good for some problems, but not for salty water.

The bottom line?

Any pasture management program should include an ongoing inventory of field measurements of water EC of all water sources stock will drink. It need not be expensive and learning will take place as the monitoring program carries on. Field EC meters will set you back a grand or two depending on bells and whistles. One person should be trained and be responsible for the measurements and the records which will be passed on if staff changes. Some lab measurements will be needed but only to keep the field program honest.

Let us hope that such losses can be relegated to history.

About the author

Columnist

J.L.(Les) Henry is a former professor and extension specialist at the University of Saskatchewan. He farms at Dundurn, Sask. He recently finished a second printing of “Henry’s Handbook of Soil and Water,” a book that mixes the basics and practical aspects of soil, fertilizer and farming. Les will cover the shipping and GST for “Grainews” readers. Simply send a cheque for $50 to Henry Perspectives, 143 Tucker Cres., Saskatoon, Sask., S7H 3H7, and he will dispatch a signed book.

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