Category Archives: Irrigation Water

Bicarbonate in Irrigation Water (part 2)

This week I visited a wholesale nursery grower in the Sebastopol, California area.

Yellowing of young nursery plants (iron chlorosis) due to elevated levels of bicarbonate in irrigation water.

They had very high levels of bicarbonate in their irrigation water (above 220 ppm [3.6 meq/L]).  Because of the high bicarbonate levels, many of the plants were showing severe iron deficiency symptoms (iron chlorosis).  High bicarbonate levels in the soil and/or irrigation water can lead to iron deficiency in crops and other plants.

Chlorosis is generally a symptom of cellular iron (Fe) deficiency that results from a limited availability of apoplastic Fe in the leaf.   However, it is often not necessarily associated with a deficiency of soluble iron in the soil solution, or a decrease in Fe uptake by the roots.  An elevated bicarbonate concentration of the soil has been identified as a major factor for the induction of chlorosis in various crops/plants.   Bicarbonate-induced chlorosis is caused by transport of bicarbonate into the stele that leads to an alkalinization of the xylem sap and, in turn, of the leaf apoplast.  Symptoms of iron deficiency develop at a high apoplastic pH due to a repression of Fe3+ reduction, which is a prerequisite for iron uptake by mesophyll cells.

With irrigation water, levels of bicarbonate + carbonate  above 3.0 meq/L are considered harmful; also because of calcium in the soil that is precipitated out as lime as the soil dries (see the Bicarbonate in Irrigation Water (part 1), posted yesterday). 

If you have any questions about high bicarbonates or iron deficiency, or any other problems with your soils or irrigation water, contact us and we can help.  Dr. B.

Bicarbonate in Irrigation Water (part 1)

Bicarbonate + Carbonate:  Irrigation water that contains levels of bicarbonate plus carbonate (especially above 3.0 meq/L (183 ppm) [combined]) are considered very harmful for two primary reasons.  Reason #1:  Bicarbonates and carbonates will combine with calcium to form lime (CaCO3) when the water evaporates.  This results in several negative consequences: (1) when free lime forms, any available beneficial calcium will be precipitated out, further compounding problems of not having enough calcium in the soil (most soils in California, Washington, Oregon and the rest of the western United States fall into this category); and (2) bicarbonate itself is the most toxic anion that exists in relation to plant health (more on this tomorrow, which is “Reason #2”). 

Wine grapes irrigated with high levels of bicarbonate in the water, leading to serious soil structure problems, erosion, and water runnoff.

To compensate, the addition of calcium to the irrigation water (e.g., in the form of solution-grade anhydrite or gypsum) will help a lot with any calcium precipitated out as lime.  Also, an acid (e.g., N-pHuric or sulfuric) can also be added to the water to neutralize the bicarbonates and carbonates, maintaining an optimum water pH of approximately 6.5.

Also ♫:  100-ppm of anything in the irrigation water amounts to 270 lbs. per acre-foot of water. Many crops may use 2.5 acre-feet of water.  If, for example, your irrigation water contained 350 ppm bicarbonate (very common in California), you could deliver an astounding 2,363 lbs. of bicarbonate per acre into your soil.  Each pound of bicarbonate ties up one pound of soluble calcium.  Reason to give bicarbonates in irrigation water serious attention.  If you have high bicarbonates and/or water penetration or soil structure problems, contact us and we can help you.  Dr. B.

Grape Soil Problem

Flooded chardonnay vineyard: Lodi, California

This photo was taken yesterday 15 March 2010 east of Lodi, California. No… the chardonnay vineyard has not been irrigated [it’s a drip irrigation system], and there hasn’t been excessive amounts of rain, either. Yet, the entire bottom half of the vineyard is under water… a serious anaerobic condition for the vines. We are seeing more and more serious water penetration problems like this, and the primary problem is irrigation water that is snow-melt runoff contributing to serious soil structure issues. This soil condition can easily be corrected, but without help, the vineyard and the grapes are in serious trouble. If you have a water penetration problem like this, call us… we would gladly talk to you about our services and how we can help your crops, whether it be grapes, almonds, vegetables or field crops, …or something fun like pussytoes (Antennaria plantaginifolia) or red undies  (Begonia sinensis)… we can help you do a better job with your production.