QUALITY AND INTERPRETATION OF IRRIGATION WATER

The quality of irrigation water depends on its chemical composition. The concentration of mineral components in water varies depending on the amount of soluble ions found in water. These soluble components are called soluble salts. If there are many soluble salts, they can be harmful to plants. The most common soluble salts are cations: sodium (Na), calcium (Ca), magnesium (Mg) and potassium (K), as well as anions: carbonate (CO₃), bicarbonate (HCO₃), chloride (Cl), sulfate (SO₄) and nitrate (NO₃).

The total level of soluble salt is determined by the electrical conductivity. Because cations are positively charged and anions are negatively charged, they will conduct electricity. The more ions, the easier it will conduct an electric current to give readings of soluble salt.

The higher the electrical conductivity, the higher the risk of salinity. Interpretation of the danger of salinity can be found in the table below.

In addition to soluble salts, it is necessary to analyze the level of sodium in water. The presence of high sodium content can reduce the penetration of water into the soil. The hazard of sodium water for irrigation is assessed by calculating the sodium adsorption factor (SAR).

If the sodium cation is predominant in irrigation water, constant use of water will adversely affect the physical condition of the soil. Sodium replaces the exchange of calcium and magnesium, causing the dispersion of clay. This dispersion destroys soil aggregates, so the soil seems slippery in the wet state and very hard in the dry. In addition to reduced permeability, other problems include slower seed germination, less soil aeration, and more difficult disease and weed control due to stagnant surface water.

Permeability problems are also related to the content of carbonates and bicarbonates in irrigation water. When the soil dries, some of the calcium and magnesium precipitates in the form of Ca-Mg (lime) carbonates. This removes Ca and Mg from groundwater and increases the risk of sodium. Recent studies have developed a method for assessing the effects of carbonate and bicarbonate on the risk of sodium. The new procedure uses a modification of the specific absorption coefficient and is called the adjusted absorption coefficient.

Interpretation of adjusted SAR for different soil types

In addition to salinity and sodium hazard, chlorides, bicarbonate and boron are potential hazards to irrigation water.

Potential hazards to irrigation water quality

Potential dangers	Content	Interpretation
Chloride (ppm Cl)	< 140 140 – 350 > 350	No problem Growing problem A difficult problem
Bicarbonate (ppm HCO3)	< 180 180 – 520 > 520	No problem Growing problem A difficult problem
Boron (ppm B)	< 0,75 0,75 – 2,0 > 2,0	No problem Growing problem A difficult problem

The quality of water needed for animals

A large amount of clean water for livestock is important for optimal productivity and animal health. Water quality is difficult to visualize, so laboratory analysis is required. There are several indicators of water quality that can lead to poor animal health or reduced livestock productivity. Such parameters are the total amount of dissolved solids, electrical conductivity, hardness, sodium content, pH, nitrates, sulfates, toxic nutrients or contaminants, as well as Escherichia coli bacteria.

The total amount of dissolved solids is a measure of all inorganic components or minerals that are dissolved in water. The most common soluble salts in water are combinations of sodium, calcium and magnesium ions with sulfate, chloride and bicarbonate ions. High salinity water can affect animal health, leading to diarrhea, excessive water consumption, mineral imbalances and reduced productivity.

Electrical conductivity measures the amount of dissolved solids, and the electrical conductivity of water is related to cations and anions dissolved in the water source. Common cations in water include calcium, magnesium and sodium. Anions include chloride, sulfate and bicarbonate. Water with higher salinity has a higher electrical conductivity. Animals typically consume water with high salinity because it creates an electrolyte imbalance that manifests itself through symptoms including dehydration, diarrhea, fever, and decreased production.

Use of salt contained in water

Hardness is expressed as the total amount of calcium and magnesium ions in the water, in the form of calcium carbonate (CaCO₃). Although hardness is not in itself a factor in animal productivity and health problems, hard water can lead to excessive calcium and / or magnesium intake, leading to mineral imbalance problems in combination with a balanced diet.

Recommendations for water hardness

Category	Hardness (ppm)
Soft	0 – 60
Moderately heavy	61 – 120
Heavy	121 – 180
Very heavy	> 180

Sodium in water in high concentrations may have a diuretic effect on animals. This makes the animal feel thirsty, it drinks more toxic water, which dehydrates its body. Sodium also interacts with sulfates, which is more risky if the water is high in sodium sulfate. Chloride deficiency may occur when adjusting your diet to a diet high in sodium. Water with a sodium content of more than 50 ppm should not be used for poultry. Salt in the diet of pigs should be reduced if the level of sodium in the water exceeds 400 ppm. In meat and dairy cattle, salt intake should be reduced if the sodium concentration in the water exceeds 800 ppm.

The pH has not been clearly defined for different livestock species, but current recommendations for beef cattle and pigs are to maintain a pH between 6.5 and 8.5.

Nitrates are found in most feeds and sometimes in water. Nitrates are not toxic in themselves, but during digestion, intestinal bacteria convert nitrates to nitrites, which then enter the bloodstream. There, nitrites convert the red pigment hemoglobin, which carries oxygen from the lungs to the tissues, into methemoglobin, a dark brown pigment that cannot carry oxygen. Nitrate poisoning is usually a bigger problem in pregnant and newborn animals. Older animals that can tolerate higher levels of nitrates. High levels of nitrates in water are often caused by shallow groundwater levels, leaching of nitrates from sandy soils, or difficult application of nitrogen fertilizers.

Use of water containing nitrates

Sulfates include sodium sulfate, magnesium sulfate and calcium sulfate. These compounds have a laxative effect on animals. Water with a high content of sulfates is a problem for animal health.

Use of water containing sulfate

SO4-S ppm	Comments
< 50	Safe for all types of livestock
< 500	Safe for most livestock, not recommended for poultry
500 – 1000	Safe for most livestock, not recommended for poultry, not recommended for young ruminants
1000 – 6999	Dangerous for ruminants and poultry, is acceptable for pigs
> 7000	Toxic to all livestock

Contaminants or nutrients present in the water may include: aluminum, arsenic, beryllium, boron, cadmium, cobalt, copper, fluorine, lead, manganese, mercury, molybdenum, nickel, selenium, vanadium and zinc.

Suitability of drinking water

If the nitrate level exceeds 10 ppm, there is cause for concern. A safe alternative source of water should be found for infants six months of age and pregnant mothers because of the risk of prenatal methemoglobinemia. This level is less critical for adults.

Boiling water does not reduce nitrate levels

Drinking water: bacteriological testing

General coliform analysis is the test most often used to determine the purity of drinking water. Coliforms are used to assess water quality because their detection is more reliable. Coliform bacteria are indicator organisms in aqueous microbiological analysis. Coliforms are a group of bacteria that are easily found in the soil, decomposing vegetation, animal feces and surface water raw materials. They are usually not present in deep groundwater and treated surface water. These indicator organisms may be accompanied by pathogenic microorganisms, but usually do not cause disease in healthy people.

Pathogens appear in smaller numbers than coliforms, so they can be isolated less often. Drinking water containing coliform bacteria is considered biologically contaminated.

Proper disinfection of water wells

The method of disinfection will differ depending on the type of well (dug, drilled, etc.). It is good to pump water until it is clean. Then the whole water system must be disinfected.

Chlorine is a universal disinfectant used in water. It is available in many forms, but two forms are most commonly used: dry chlorine (calcium hypochlorite) and liquid sodium hypochlorite, commonly referred to as “home bleach”, which contains approximately 5.25% chlorine available.

When chlorine is introduced into wells, reservoirs and piping systems, proper distribution and disinfection of all parts of the water system must be ensured.

One convenient way to chlorinate a water supply is to add chlorine directly to the well. An effective hypochlorite solution can be made by adding the required amount of bleach. This chlorinated water should be poured into the well, washing the walls, housing, and other equipment in the process. If after a reasonable period of washing (approximately 10 minutes) the smell of chlorine is not felt, you need to repeat the procedure until the smell of chlorine.

After the recirculation process, the well components should be idle for approximately two hours. The taps should be closed and the chlorinated water residue washed away until all traces of chlorine have disappeared, as traces of residual chlorine interfere with laboratory results.

Small wells may remain contaminated for some time due to surface leakage. Therefore, at least two weeks after the soil has dried, the water should be boiled or chlorinated before use. Boiling for three minutes or adding two drops of household bleach is enough for a satisfactory result.

Drinking water sampling procedures

Water samples should not be taken from external hydrants, leaky water taps and taps with attached aerators or filters, as they can give positive results when the water from the well is actually safe. Special containers are required for biological research

“Satisfactory” bacteriological analysis of water is not a guarantee that the water supply system will continue to be safe. Water quality depends on many variables: proper construction, well location, groundwater level, soil formation, flooding, and so on. It is recommended to analyze the water at least once a year when repairing or changing the water supply system, or if you suspect possible contamination of your well.