Soil pH and Buffer pH, what does it mean

Soil pH

This is a measure of the soil acidity or alkalinity and is sometimes called the soil "water" pH. This is because it is a measure of the pH of the soil solution, which is considered the active pH that affects plant growth. Soil pH is the foundation of essentially all soil chemistry and nutrient reaction and should be the first consideration when evaluating a soil test. The total range of the soil pH scale is from 0-14. Values below the mid-point (pH 7.0) are acidic and those above pH 7.0 are alkaline. A soil pH of 7.0 is considered to be neutral. Most plants perform best in a soil that is slightly acid to neutral (pH6.0-7.0). Some plants like blueberries require the soil to be more acid (pH4.5-5.5), and other, like alfalfa will tolerate a slightly alkaline soil (pH 7.0-7.5).
Figure 1: pH Scale Progression

The soil pH scale is logarithmic; meaning that each whole number is a factor of 10 larger or smaller than the ones next to it. For example if a soil has a pH of 7.0 and this pH is lowered to pH 6.0, the acid content of that soil is increased 10-fold. If the pH is lowered further to pH 5.0, the acid content becomes 100 times greater than at pH 7.0. The logarithmic nature of the pH scale means that small changes in a soil pH can have large effects on nutrient availability and plant growth.
Buffer pH (BpH)

This is a value that is generated in the laboratory, it is not an existing feature of the soil. Laboratories perform this test in order to develop lime recommendations, and it actually has no other practical value.
In basic terms, the BpH is the resulting sample pH after the laboratory has added a liming material. In this test, the laboratory adds a chemical mixture called a buffering solution. This solution functions like extremely fast-acting lime. Each soil sample receives the same amount of buffering solution; therefore the resulting pH is different for each sample. Too determine a lime recommendation, the laboratory looks at the difference between the original soil pH and the ending pH after the buffering solution has reacted with the soil. If the difference between the two pH measurements is large, it means that the soil pH is easily changed, and a low rate of lime will be sufficient. If the soil pH changes only a little after the buffering solution has reacted, it means that the soil pH is difficult to change and a larger lime addition is needed to reach the desired pH for the crop. The reasons that a soil may require differing amounts of lime to change the soil pH relates to the soil CEC and the "reserve" acidity that is contained by the soil. Soil acidity is controlled by the amount of hydrogen (H+) and the aluminum (Al+++) that is either contained in, or generated by the soil and soil components. Soils with a high CEC have a greater capacity to contain or generate these sources of acidity. Therefore, at a given soil pH, a soil with a higher CEC (thus a lower buffered pH) will normally require more lime to reach a given target pH than a soil with a lower CEC.
Figure 2: Coffee Pot Analogy for Buffer pH

The following analogy (adapted from University of Nebraska, Bulletin G74-153) may give a simple explanation. Consider two-coffee pots (figure A) one 50-cup capacity and one 10 cup, both having the same size indicator tube and spigot. Coffee in the indicator tube represents the active acidity (measured by regular pH) and that coffee in the pot represents the reserve acidity (measured by buffer pH). Let the large pot represent a clay soil high in organic matter while the small pot represents a sandy soil. Both pots have equal amounts of coffee in the indicator tube; i.e., same active hydrogen, so same soil pH.
Now open the spigot and remove one-cup of coffee from each pot (figure B). Removing one cup of coffee from each pot could be equated to the addition of small amount of limestone to an acid soil. Opening the spigot will cause the level of coffee in the indicator tube to drop below the level in the pot, but will return to almost the original level (clay soil) when the spigot is closed. The momentary drop of coffee in the indicator tube represents the initial increased in pH when lime is added (affects active hydrogen), but reserve hydrogen (similar to coffee in the pot) soon equalizes the effect from the lime and the pH returns to essentially its original level (clay soil, figure C). Thus, if the pH is 6.5 or lower, a buffer pH is run to measure the reserve acidity. The result of the buffer pH shows the amount of lime required to neuralize a major portion of the reserve acidity. The relative amounts of coffee in the two pots (figure C) show why a sandy soil and clay soil with the same pH result in different lime requirements. For example, the small addition of limestone (equivalent to removing one cup of coffee from each pot) reduced the total coffee (reserve acidity) by 10% in the small pot (sandy soil), but only 2% of the large pot (clay soil). In a similar manner, 1 ton of agricultural limestone will make a greater difference in the pH of a sandy soil than of a clay soil.

Source: Spectrum Analytic

so for those that think buffered means we dont need to ph food...need to read this. both organic and non work this way...food is food

Nutrients

All plants, weather grown hydroponically or in soil, need 16 basic elements to grow. Most of us are familiar with the top three that are consumed by plants. These elements are called the Macro-Elements and they are Nitrogen Phosphorous and Potassium, they are abbreviated N P K. You probably have seen these letters on bags of common fertilizer. The other 13 elements are grouped together as the Micro-Elements. Most people are not familiar with these elements because we have always counted on them being present in the soil, which works for the most part.

Pre-Formulated Nutrients: This is really the best option for the hobby to small farm hydroponic grower. You can be assured that all of the necessary nutrients are present and available to the plants. All you have to do is mix a predetermined amount of concentrate with water and add it to your system. If you want to be successful as a first time hydroponic grower, use a ready made nutrient specifically for hydroponics.
Pre-Formulated Nutrients come in the forms of 1-part powders, 2-part powders, 1-part liquids, 2-part liquids, & 3-part liquids. I have found that nutrients are pretty much nutrients, with the exception of the General Hydroponics 3-part flora series. This one nutrient system really stands out above the rest, it gives the best results by far. You can customize the mix for specific crops and different phases of the crop (i.e. one mix for vegetative growth and another for flowering/fruiting phases of growth).

Formulating your own: Once you have some experience with hydroponics and you are producing large crops of a specific plant, you may want to look into formulating your own nutrients. Since all plants do not consume the same amounts of nutrients (individual elements) you can possibly save yourself some money by making very specific formulas for your crop. This involves a good amount of chemistry knowledge, some lab equipment and each of the 16 individual elemental nutrients. Many crop specific formulas exist from others' research, all you have to do is find the right recipe and mix it up. Over time you will probably adjust this formula to match your growing conditions and crop more closely. Mixing your own is best left to the more experienced who are producing large amounts of one crop (i.e. 1/4 acre on up).

Miracle Grow: Many people insist on trying to use miracle grow plant food as a hydroponic nutrient. It is true that this is great stuff for soil, I personally use it on my flowers, grown in the dirt garden, and man do they freak out. Let me stress though, this stuff is not a complete nutrient for hydroponics. It does contain some micro elements, but not all. Your plants will start out fine using this, but eventually they will suffer from deficiencies. In the long run it is not worth the cost savings over a real hydroponic nutrient. The analogy would be something like buying a brand new corvette and then having the cheapest tires put on it and filling up with the cheapest gasoline. You will not even come close to getting the performance that is possible.


Nutrient Additives

There are quite a few hydroponic additives on the market. They mainly consist of combinations of kelp extracts, bone meal and blood meal. They are commonly sold as "Organic" boosters just to hook the "green" crowd. They are supposed to supply enzymes, hormones, vitamins, amino acids, sugars, and plant acids that can't be supplied by hydroponic nutrients. I believe that there are some merits to using these additives, but many of the claims made by these products are UNFOUNDED and UNTRUE. I have tried the "Earth Juice Catalyst" and I THINK that I saw a performance increase, but nothing major. In the future I will perform an experiment with a control group of plants to see how this stuff really performs.
One additive that falls in it's own class is the "DynaGRO PRO-TEEKT". It is a potassium and silicon supplement that is supposed to help increase resistance to pathogens, increase resistance to heat stress and build stem strength. I have yet to try this product.
The bottom line on additives: There are no scientific studies showing any benefits so the jury is still out. Buyer beware!!


pH

pH is simply the measure of the acid content of a solution. The pH scale runs from 1 to 14, 1 being very acidic, 7 is neutral, and 14 is very basic. pH affects the ability of a plant's roots to absorb nutrients. The range in which nutrient absorption is best is from 5.8 to 6.5.
Measuring pH: You can measure pH either chemically or electronically. Chemical test kits cost about $8 to $18, they are accurate but you have to replace them periodically because the chemicals are consumed. Electronic methods typically are packaged as a pen that you simply dip into the solution and the pH is read out on a digital LCD display. pH pens cost about $65 to $100, they are fairly accurate and must be calibrated periodically. The benefit is ease of use and they don't wear out - a wise investment.

Adjusting pH: To lower pH add acid. The best acids to use are phosphoric, nitric, and sulfuric acid, these acids disassociate and free up phosphorous, nitrogen an sulfur respectively. Nitrogen, Phosphorous and Sulfur are all elements that plants need for growth. I have heard of people using Distilled Vinegar for pH adjustment, this seems a bit sketchy to me but I suppose it would word in a pinch.
To raise pH add a base. The bases used in hydroponics are Potassium Hydroxide and Sodium Hydroxide. These disassociate and provide Potassium and Sodium, respectively. Another pH up "elixir" that I have heard of is baking soda - personally I think this is a bad idea.

TIP! When adding acid or base to adjust your nutrient solution, add small amounts at a time and wait about 1/2 hour to take a measurement. The closer your pH is to 7, the less acid or base it takes to effect change. This change takes place exponentially, for example: it can take two milliliters of acid move the pH of 25 gallons of nutrient from 7 to 6. From 6 to 5 it can take 8 milliliters, from 5 to 4 it can take 500 milliliters. BE CAREFUL and make changes slowly.

Making your own pH adjusting solutions: One quart of acid or base from General Hydroponics retails for about $7.00. This is the biggest rip off in the hydroponic business! It takes about $10.00 of concentrated acid or base to make 2000 gallons of pH adjusting solution. Subtract packaging and shipping and you'll see that they turn $10 into $4000. OUCH!!!!!

Organic Nutrients (??????)

With the relatively recent green movement the concept of "Organic" food production rings louder and louder every day. "Organic" guidelines generally prohibit the use of any refined chemicals in food production. The result is fertilizers derived from compost and animal waste.

Naturally people want to try to apply these principles to hydroponics in the form of a teas made from compost and other natural ingredients. This seems logical but the result is counter productive when used in a hydroponics environment. To understand why, we must first understand what nutrients are and how they are absorbed by plants.

Plants rely upon sixteen basic chemical elements for food - Nitrogen, Potassium, Phosphorus, Calcium, Hydrogen, and Oxygen are just a few. These elements must be in a form that can be absorbed by a plant. This form is a chemical salt - a very basic chemical compound containing one of the sixteen elements and a complementary element that forms a salt. These "elemental" salts are what is absorbed from the soil by a plant's root sysetm. To be perfectly clear here - it is salts and only salts that a plat absorbs, nothing else.

So, the big question is - In the natural"organic" cycle of things how do these chemical salts get into the soil? Let's start with organic material (compost) and follow it to absorption by the plant. A bit of compost contains complex organic chemical chains that contain the elements for the chemical salts that eventually will be absorbed by a plant. At this point these complex chemicals cannot be used by a plant. When the compost gets mixed into the soil it starts to be acted upon by soil born bacteria. This bacteria is what breaks the organic material down into the chemical salts that can be used by plants.


Organic material + Soil Born Bacteria = Nutrient Salts



Mother Nature uses bacteria to refine organic material into inorganic chemical compounds for plant absorption. In a hydroponic system sufficient bacteria are not present for this critical conversion, instead we must provide these refined chemicals directly to the system.

For those who insist that they can do it "organically" there are some "organic" nutrient mixes available for you to try. They typically produce limited results that I believe is entirely counterproductive to the hydroponic philosophy. I suggest that if you want to grow organically, do it in the dirt. Heavily supplement your soil with natural fertilizers and you will get excellent results. I do this in my own dirt garden and everything grows wonderfully.

Oxygen



Putting it all together

Overview: In order to get your feet wet with hydroponics we are going to choose a simple, low maintenance hydroponic system and grow a hearty medium growing speed plant in order to keep nutrient usage to a minimum. Use a one-part nutrient (just mix with water) and unless you live in an area with EXTREMELY hard water don't worry about pH. The system: I highly recommend using the "Aquafarm" type bucket based system (see the free plans) for starters. They are extremely cheap and require practically no effort to operate.
The Plants: To begin with grow a semi-hearty cannabis such as thyme, mint, or basil. These plants are basically weeds and don't care too much about having a critical nutrient or pH balance. Also, since they are a weed, they really go nuts when you give the hydroponic treatment. We also choose this type of plant because it is relatively slow growing and won't be using large volumes of nutrient solution. In the peak of the growing season, plants like tomatoes, squash and cucumbers can use many gallons of nutrient per day. Avoid these in the beginning otherwise you will be constantly worrying about maintaining nutrient levels - later on you'll see that with a bigger commitment, there are simple ways of maintaining the nutrients automatically.
Nutrients: Initially, I recommend using a one-part nutrient such as the General Hydroponics "Flora-Magic". It is a one-part powder that you simply mix with water.
Maintenance: The only thing you'll need to do is monitor the nutrient level in your hydroponic system topping the level off with water between scheduled nutrient changes. Initially, your young plants will not use much nutrient at all, so changing the nutrient once every two weeks is sufficient. Once the plants start consuming the nutrient then a once-a-week change is in order. Drain the old nutrient into your flower beds (it's still good stuff) and recharge the system with fresh.
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little more.....

http://www.eutechinst.com/tips/ph/15_soil_ph.pdf

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