Are California Farmers Water Hogs?

In his commentary in the Wall Street Journal, California Farmers Aren’t the Water Hogs, Ted Sheely discusses the blame farmers are asked to take for the water shortage in California.

Sheely, a farmer himself in California’s San Joaquin Valley, argues that the media is not reporting the full picture.

“The second-worst thing about the drought is how farmers are bearing most of the blame. We hear one figure over and over: Agriculture consumes 80% of California’s water.

That statistic makes farmers like me look like gluttons—and it suggests that if we were to reduce our reliance on water just a little, then our state’s predicament would vanish like a puddle on a hot day.

Except that it’s not true. Farmers don’t use 80% of California’s water. While this figure has saturated the media’s coverage of the drought—it’s a fabrication of environmentalists who want to disguise that they “use” even more water than farmers.”

FarmlandFarmland

Farmland in Los Banos, Calif., in the San Joaquin Valley. PHOTO: LUCY NICHOLSON/REUTERS

Read the entire story in the Wall Street Journal: California Farmers Aren’t the Water Hogs

SOIL AND WATER CHEMISTRY PROBLEMS, SOLUTIONS AND FACTS (PART 3)

WATER

Water quality is highly dependent on the source of the water, which in most irrigated agriculture is either from snowmelt runoff or from underground aquifers accessed by wells.  Snowmelt runoff is lacking the salts necessary to maintain soil and crop health in California, the West, and many other parts of the world.  Inversely, well water sources often contain excessive amounts of salts, which are detrimental to crop and soil health. Both situations require calcium sulfate applications to sustain crop and soil health.

Snowmelt Runoff: Not Enough Salts:

A critical property of irrigation water is ECw, electrical conductivity of the irrigation water, (the amount of total dissolved salts in the irrigation water).  The problem with using water from snowmelt runoff is the low amount of total dissolved salts it contains (ECw).  Since pure water does not conduct electricity and salty water does, the more salts in the water the greater the conductance of electricity.  The rule of thumb for ECw is: if less than approximately 0.60 decisiemens per meter (dS/m), then calcium must be added.  The reason is because the pure water is contributing to leaching beneficial calcium below the root zone over time, and is not being replenished.

The application of EcoGEM’s calcium sulfate will quickly and effectively remedy low-salt irrigation water problems.

High Salts (Both Soil and Irrigation Water):

The opposite of when irrigation water is too pure is when the water contains too much salt. When soil and/or water have too much salt, the sodium, chloride and other harmful salts have detrimental effects on plants not only from the aspect of high levels of sodium in the soil in relation to levels of calcium, but also from high salts themselves.  Besides destroying soil structure, high salts in waters and soils can be harmful or fatal to the crops/plants when it accumulates in the root zone.  Sodium and chloride are particularly toxic to ornamentals and woody plants.

About 1/3 of all soils in the arid and semiarid regions of the United States have some degree of salt accumulation, primarily the anions Cl, SO42-, and HCO3 of the cations Ca, K, Mg, and Na.  The primary sources of these salts are weathering of rocks and minerals, ground and irrigation water, and fertilizers.

Once deposited or released in the soil, the salts move to or remain near the surface of the soil by upward-moving water, which then evaporates, leaving the salts behind.  Most crop plants cannot tolerate high levels of salts; therefore, placing limitations on some salt affected soils.  Salt buildup in an existing or potential danger on all irrigated land in the United States.  Continual application of water, all of which contains salts (especially reclaimed water), will continually increase the soluble salts in soils unless the soils have good soil structure and periodic leaching.

By cationic exchange reactions, calcium is used to replace sodium in saline and sodic (high sodium) soils (reaction 7 above).  The calcium will replace any sodium on the cation exchange complex (CEC).  What happens chemically is: calcium solubilized from gypsum replaces sodium leaving soluble sodium sulfate (Na2SO4) in the water, which is then leached out.

This is another reason for the application of EcoGEM’s calcium sulfate. Of all calcium compounds gypsum is considered the most convenient and inexpensive for this purpose.

High Bicarbonate in Irrigation Water:  Add an acid source to neutralize the bicarbonate in irrigation water so additional free lime (CaCO3) in the soil or irrigation system cannot form (reaction 4 above).  Also, the addition of gypsum to irrigation water will replace any calcium precipitated as free lime and will remove any bicarbonates from the soil solution (reaction 6 above).

Bicarbonates and carbonates will form free lime when the water evaporates (reaction 1 above), and this results in several negative consequences:

  1. When the water evaporates, the free lime has the ability to raise the pH of the soil and reduce available calcium. Also when free lime forms, available beneficial calcium will be precipitated out, further compounding the problem of not having enough calcium in the soil.
  2. The reduction of available calcium leads to loss of soil structure and reduced water infiltration that also reduces the normal leaching process by which salt buildup in the root zone is prevented.

Note:  Bicarbonate is also the most toxic anion that exists in relation to plant health.  Any amount in excess of 5.0 milliequivalents per liter (meq/L) is considered very high.

Benefits of Acid Injected Into Irrigation Water:

There are many forms of injectable acids that include (but are not limited to) N-pHERIC, pHAIRWAY, phos acid, sulfuric acid and sulfur burners.  Farms/parks/grounds are able to utilize acid for neutralizing bicarbonate and in some cases to increase water infiltration.

With the injection of acid into the irrigation water, hydrogen (H+) neutralizes the bicarbonate into water and carbon dioxide (reaction 2 above).  Acid can be introduced to the irrigation water either by a liquid acid (one of the above sources) or by a sulfur burner, which ultimately injects sulfuric acid into the irrigation water.

The pH of the irrigation water is usually lowered to a level of 6.0-6.2.  When the pH of the water is at this level, the amount of bicarbonate that remains in the water is approximately 1.0 me/L. While the addition of acid to the irrigation water will neutralize bicarbonate, there is a limited increase in water infiltration.  Since the pH of the water is not very acidic, the water is applying only a small amount of acidity or free hydrogen to the soil.  The acid will, therefore, neutralize only a small amount of free lime in the soil.  The neutralized lime will ionize to calcium ions (reaction 5 above)] therefore improving water infiltration.  As the free lime is neutralized in the top three-six inches of the soil, the acid will have less free lime to react with thus reducing the water infiltration.  Since the acid is primarily neutralizing the bicarbonate in the water, there will be less free lime being deposited on the soil for the acid to react with.

The first year of water injected acid applications, the water infiltration does tend to improve.  However, in the second and subsequent years the infiltration will return to its original disorder.  That is why the addition of EcoGEM’s calcium sulfate (gypsum) along with the acid is recommended to help amend and maintain soil structure.

SALINE/SODIC CLASSIFICATION OF SOILS

Class                           E.C. (ds/m)        pH           SAR (or ESP)       Soil Physical Condition

Normal                      <4                   <8.5                            <15                 Normal

Saline                         >4                   <8.5                            <15                 Normal

Sodic                          <4                   >8.5                            >15                 Poor

Saline/ Sodic            >4                   > or <8.5                    >15                 Poor

SOIL AND WATER CHEMISTRY PROBLEMS, SOLUTIONS AND FACTS (PART 2)

SOIL

Low pH Soil:

Add CaCO3 (lime) to neutralize the acidity, which will increase the soil pH (reaction 5 above).  Even though CaCO3 is a salt, it acts as a base in an acid soil.  Consequently CaCO3 causes the following events to occur in an acid soil, most of which take place simultaneously:

  1. Acidity is neutralized
  2. Base saturation (Ca and Mg) of the soil increases
  3. Ratios of basic cations adsorbed and in solution change
  4. Soil pH increases (as soon as the CO2 dissipates away), which in turn affects the solubility of most of the plant nutrients in a soil
  5. Toxic concentration of Al3+, Mn2+, and possible other ions, are neutralized (or otherwise inactivated)
  6. Acid weathering of primary and secondary minerals is curtailed by the decreased concentration of H+
  7. pH-dependent cation exchange complex (CEC) (i.e., negative charge) increases, adsorbing Ca2+ and Mg2+ from which it is hydrolyzed (mobilized) for ready uptake by plants or movement to lower depths in the profile
  8. pH-dependent anion exchange capacity (AEC, i.e., positive charges) decreases, forcing previously adsorbed anions such as SO42- into solution
  9. Dinitrogen fixation increases
  10. Nitrogen mineralization from plant residues and soil organic matter increases
  11. Electrolyte concentration increases with dissolution of lime, and where CEC dominates over AEC, the electrolyte disappears from solution as CO2 volatilize
  12. Hydroxyl ion (OH) concentration increases with dissolution of lime, and where AEC dominates over CEC, the increased OH ion concentration neutralizes + charges, forcing SO42- into solution

High pH Soil:

Add acid (H2SO4 or another acid source) to dissolve the free lime (CaCO3) that will lower the pH in the soil and ultimately produce Ca2+ and SO42- ions (gypsum) (reaction 4 and possibly 3 above).  Ionized calcium is now able to attract or flocculate the soil colloids thus increasing water infiltration.

SOIL AND WATER CHEMISTRY PROBLEMS, SOLUTIONS AND FACTS (PART 1)

Brent Rouppet, Ph.D., Soil  Scientist / Agronomist

Legend of Chemical Symbols

 

CaSO4·2H2O              gypsum (as it exists in nature)

Ca2+                            calcium ion (the form of calcium that plants use)

CaCO3                         free (or pure) lime (or limestone)

HCO3                         bicarbonate (the most toxic anion for plants)

Cl                               chloride ion

H+ (acid)                    the generic chemical symbol for any acid

OH–                                            hydroxyl ion

CO2                             carbon dioxide (an atmospheric gas)

S                                                   elemental sulfur (as it exists in nature)

SO42-                           sulfate ion (the form of sulfur that plants use)

K+                                                potassium ion

Na+                             sodium ion (very toxic to plants and harmful to soil structure)

Mg2+                                         magnesium ion (harmful to soil structure when insufficient calcium is present)

soil                             a soil particle that has a net negative electrical charge (attracts positively charged ions; e.g., sodium, magnesium, calcium, etc.)

Na2SO4                       sodium sulfate.  A non-electrically charged salt that can be leached through the soil with irrigation water

Common Soil and Water Chemical Reactions

2HCO3(bicarbonate) + Ca2+ (calcium ion)     →     CaCO3 (free lime)     + H2O    +     CO2

HCO3 (bicarbonate) + H+ (acid)     →     H2O   +     CO2

2S (elemental sulfur) +      3H2O     +     3O2    →       H2SO4 (sulfuric acid)

H2SO4 (sulfuric acid) +     CaCO3 (free lime)     →     Ca2+ (calcium ion)    + SO42- (sulfate ion)     +     CO2      +     H2O

2 H+ (acid) + CaCO3 (free lime)     →     Ca2+ (calcium ion)    +     CO2      + H2O

CaSO42H2O (gypsum) +     H2O     →    Ca2+ (calcium ion)     +     SO42- (sulfate ion)

Na+/Mg2+(sodium/magnesium ions)- [on soil] +     CaSO42H2O (gypsum)     →      Ca2+/Mg2+ (calcium/magnesium ions) – [on soil]     +       Na2SO4            (sodium sulfate)  [now leachable]

Building an Effective Fertilization Program Around Science-Based Nutrition (Part 2)

As an example, Dart points out that a crop developing leaves needs the right nutrient in the right form as the leaves are expanding. That’s the time to be applying zinc (Zn), phosphate, and nitrogen (N), because they drive leaf size. At the same time, you should be applying the micronutrients (magnesium (Mg), manganese (Mn), iron (Fe), copper (Cu). These are building blocks for the chlorophyll that is developing as the leaves grow and expand. If you apply these nutrients after the leaves have fully formed, or if you apply them in a form that doesn’t go into the leaf until after it fully forms, you don’t get the full value of the application.

Timing and formulation matter, which is why they are on the Five R list. Dart encourages growers to ask tough, science-based questions of anyone making nutrition recommendations to ensure they get a program that addresses all of the Five Rs. Questions he recommends include:

  • You’re recommending that I use this product — why? “Does this product have specifically and completely what I need at this stage of my crop?” asks Dart. “For example, growers need to pay particular attention to the micronutrients in their program because they drive the chlorophyll development, which is critical for photosynthesis, which in turn is critical for higher marketable yields and producing the sugars and flavor in melons and other fruit that leads to the customer coming back for more.”
  • When does my crop really need this particular nutrient and why? “The plant’s need for a particular nutrient is not a flat line through the plant’s life,” notes Dart. “Some nutrients have early peak demand, some mid or late season based on how the nutrient is used in the plant and the specific quality parameters required for that crop. Growers want to make the applications in the front end of the demand curve, not the top or
    the back end of the curve. That is when the nutrient is being used by the plant for maximum effectiveness and value.”
  • Am I over-applying anything? “This question often doesn’t get asked, so many growers end up applying too much of a specific nutrient, most commonly nitrogen. The quality of the end product can be heavily impacted by applying too much of some nutrients,” says Dart, noting that this issue doesn’t get enough attention, especially with high-value crops like melons, cucumbers, tomatoes, peppers, potatoes, or leafy vegetables.“For example, too high of a nitrogen-to-calcium ratio can hurt a crop’s texture, color, sugar, flavor, shelf life, and shipping quality, so you don’t want to push too much nitrogen and underuse calcium.” This is especially true on mid/late season nitrogen applications.
  • What is the best timing and formulation for making this application to ensure the plant will benefit from the nutrient? “This is a critical issue that can get easily overlooked, which results in wasted time and money,” says Dart. “Calcium (Ca) is a good example, because the fruiting parts of these vegetable crops can only take in Ca via foliar application during the cell division window of the fruit. At any other time, the Ca won’t go into the cell wall and be there for better texture, shipping quality, and shelf life. If you miss that window, it becomes a mis-timed application that won’t deliver the desired results and will waste money and packable yield.”“If you want to be a hero to the produce buyer and produce manager, do a better job on calcium and the Five Rs and you will reduce shrinkage — the second biggest expense in the produce department after labor costs.”
  • Why is the formulation that you’re recommending the right formulation to get this nutrient into the plant? “Delivering a nutrient the plant can use is all about the product’s formulation, and it is often overlooked in a nutrition program,” says Dart. “But the formulation matters because a foliar nutrient is only effective and has value if it gets into the plant completely and at the right time.”
  • Manufacturers are continually improving the fertilizers and nutrient products they bring to the market. Growers who understand the Five Rs and Science-Based Nutrition will be positioned to make the best choices for the best results, less waste, and increased economic returns.

Source: Growing Produce. August 2019

Building an Effective Fertilization Program Around Science-Based Nutrition (part 1)

Source: Growing Produce. August 2019

THE MULTIPLE BENEFITS OF GYPSUM

When purchasing gypsum or anhydrite, it is important to understand the many varied benefits and when they take effect in agriculture. As both a soil amendment and a crop nutrient source, both gypsum and anhyrite will remediate high magnesium and sodic soils, help manage saline irrigation waters, provide calcium and sulfur as crop nutrients, and improve soil structure. All of these benefits occur at different rates.

I invited a friend to a gypsum symposium this summer because I knew he had tried it, and he has an open mind when it comes to trying new ideas. However he declined and reminded me, “I haven’t had the best results from using gypsum in the past.” I recall a conversation we had about gypsum, and his expectation was that a gypsum application should create a response just like applications of nitrogen, phosphorus, or potassium. His was an unrealistic expectation, and my telling him so didn’t undo his perception.

Gypsum works to improve drainage in soils dominated with dispersive clays in four ways. One is immediate, one nearly immediate, the third occurs with a flush of root growth and soil biological activity, and the last is a change in structure.

First – When gypsum dissolves into soil water, it helps water move more freely. That’s an immediate effect, and it can be substantial as it improves drainage. Since gypsum doesn’t dissolve immediately, the effect is persistent. If surface ponding is an issue, gypsum should be concentrated within the first few inches of soil.

Second – Calcium displaces sodium and magnesium on the clay’s exchange sites and reverses the clay’s tendency to disperse. As flocculation and structure improve, drainage improves. This can’t happen until the gypsum has gone into solution and ion exchange occurs. The effect isn’t immediate but will happen during the season it applied. This benefit is even more persistent than the salt effect above.

Third – Once drainage improves, root growth renews, and the biology of the soil kicks in. The root flush occurs before the top growth flush can occur. This will occur in-season.

Fourth – Lastly, the process by which gypsum amends the soil is somewhat slow. It can take anywhere between 3 months and 3 years depending on the clay and organic content and the initial starting point of the soil. You might have to amend the soil for a few years to get the desired results.

If you apply gypsum to improve soil structure, set the right expectation. By 3 to 5 years after aN application of 1 to 2 tons or multiple applications of 1,000 to 2,000 pounds you should begin to see improvements in soil structure and tilth.

Dr. Dan Davidson, Agronomist. EcoGEM, Denver, CO

Plant Availability of Potassium in Soil Minerals: What’s Happening Near the Roots? (PART 2)

(continued): Plant roots can also exude their own acids and carbon compounds into the rhizosphere. These substances are released as the plant regulates the types and amounts of nutrients and other molecules in its roots. Finally, as roots take up K from the soil, they deplete K in the rhizosphere to concentrations much lower than the bulk soil. Very low concentrations of K near the root can trigger the release of K from mineral structures. All of these mechanisms arise from chemical and physical forces considered part of weathering. Rather than taking years, however, these processes working in the rhizosphere release K in a matter of days or weeks. Even with all these mechanisms, a plant may still not be able to access enough K from the soil to meet its nutritional requirements. Scientists have come up with a variety of measurements that differentiate conditions when plants are accessing enough K and when they are not. Soil tests and plant tissue tests that are calibrated to crop growth and development have been extremely helpful in this regard. Future improvements in the accuracy and precision of these tests will need to consider how plant varieties differ in their abilities to acquire K. How different varieties alter their rhizosphere environment will be an important consideration. [International Plant Nutrition Institute. Issue #1 2018]

Plant Availability of Potassium in Soil Minerals: What’s Happening Near the Roots? (Part 1)

Plants require a lot of potassium (K), and most of what plants need comes from the soil. Soils contain a variety of minerals that contain K in their structures, but that K is not readily available for use by the plant. The traditional view is that K in these minerals comes out in small quantities over long periods of time as soils age. Physical forces and chemical reactions slowly break down these minerals, a process called weathering, releasing K into the soil water where plants roots can take it up. While this traditional view is correct for the bulk soil, weathering can occur quickly in the zone of soil right around and influenced by the root. This zone, called the rhizosphere, has a chemical and biological composition much different from the bulk soil. Bacteria bloom in the rhizosphere. Bacterial populations are often several times those found in the bulk soil. As plant roots grow, they leave behind a lot of carbon. This carbon comes from dead cells and from chemical compounds they release, including mucilage, a gelatinous substance that lubricates the root tip as it extends into the soil. Soil bacteria need carbon, and the rich supply of it in the rhizosphere fuels their growth. Some of the bacteria blooming in the rhizosphere can solubilize a portion of the K in soil minerals. Although there is still a lot to be understood about how they do it, at least some of the bacteria that have been isolated and studied produce acids and other carbon compounds that break the chemical bonds holding mineral structures together. As bonds break, K gets released and becomes available for uptake by roots. Fungi are also abundant in the rhizosphere. They too need carbon. Like bacteria, some fungi exude acids that break down minerals and release K that can be taken up by the plant. In addition, fungi grow mycelia. As these tubular filaments grow, they exert physical forces on soil minerals that can also break their structural bonds and release K.  [International Plant Nutrition Institute. Issue #1 2018]

Mastering soil health elevates farm productivity, sustainability (PART 2)

by Dennis Pollock– Western Farm Press

Four soil health approaches

Mitchell said much has been learned from a research plot at the UC center where four approaches take place, including standard tillage and no cover crop, standard tillage and cover crops, no tillage and no cover crop, and no tillage and cover crops.

“Behind me is a very important field,” he said, referring to a research plot home to a growing number of crops in recent years, including cotton, processing tomatoes, corn, wheat, garbanzo beans, and sorghum.

Mitchell closed the meeting with the observation he believes it’s possible to grow still more crops using the no-till/cover crop approach which has gained more favor in the wake of years of drought. For one thing, he said the system of adding residue keeps the ground cooler which keeps soil organisms alive and saves water use.

Sloane Rice, a hydrology student at UC Davis, echoed the notion that cover crops are a key to improving water management by increasing water retention.

Other savings from no-till have long been known, including reduced labor costs, wear and tear on tractors, and savings on diesel fuel due to fewer passes across field. In addition, dust is reduced by nearly 70 percent.

Armchair scientist

Retired organic grower Tom Willey conceded there have been some challenges to those who grow organically. Willey said he struggled for 30 years to get more attention from scientists and researchers on organic production.

“I had to become an armchair scientist,” Willey noted.

He added that organic farmers “till and cultivate more intensively than their conventional brethren.”

“Until organic systems somehow learn to embrace no-till, a unique challenge in vegetable production, we’ll need to shovel lots of ‘coal’ into the firebox, possibly outstripping compost feedstock resources should acreage greatly expand,” Willey said.

He said soil-applied compost functions “like an interest-bearing savings account.” Nitrogen slowly mineralizes through secondary microbial degradation of organic matter, and nutrients are released from “predator-prey” soil interactions.

Willey said a better understanding of soil biology “is poised to take almost all of the chemicals out of agriculture. It will bring good farming and we won’t have to call it conventional or organic – just good farming.”

The new emphasis on good farming has truly moved into the soil, not just looking at yields and production of what is growing above it. It means looking at the complex interaction of microbial organisms underground and takes into carbon added to the soil.

Healthy soil = genetic diversity

Howard Ferris, UC, Davis nematologist, looked at the suppression of pest species underground, pointing out that some nematodes are beneficial in keeping problem nematode pests at bay.

He said healthy soil sustains plant and animal productivity, and provides a reservoir for genetic diversity. Organisms in the soil decompose organic materials, sequester and redistribute minerals, mineralize organic compounds, and regulate and suppress pests.

They improve soil structure and reduce soil erosion.

“With healthy soil, you can smell it,” Ferris said. “It’s healthy and alive.”

With the diversity of species in the soil comes higher levels of carbon, he said.

Radomir Schmidt, UC Davis soil microbiologist, referred to soil as part of “a solar-powered engine.” He is researching DNA sequencing of microbes, a complex process that could help in better understanding interactions of various microbes.