Physical elements {TILTH} Physical elements {TILTH} – e.g. sand, silt, clay, organic material and aggregates (see SOIL {1}) Living elements (other than plants) Living elements (other than plants) – e.g. nematodes, earthworms, fungi, protozoa, bacteria, insects, spiders, mites… (see SOIL {2}) Chemical elements Chemical elements –pH and its effect on nutrients (primary, secondary and micro- nutrients); water;oxygen SOIL

pH A controversial topic!!??

pH – a controversial topic

Author has gardened in Oregon, Canada, California and now lives in Australia – the article was adapted from a book published by MOTHER EARTH NEWS titled, “Book for Wiser Living”.

Research based information The previous two slides were not from a source that bases its findings on research. When looking for accurate information online, be sure the source ends with.edu or.gov.

Soil pH is one of the most important soil measurements. It plays a huge role in the availability of nutrients to plant roots, nutrient run-off, leaching and microbial efficiency Soil pH is one of the most important soil measurements. It plays a huge role in the availability of nutrients to plant roots, nutrient run-off, leaching and microbial efficiency Significance of pH

pH 6.5 pH 3.8 & 5 Low pH (5 and below) and low Ca result in damage to root membranes. Root development of tomato plants in self-watering containers

Root development in self- watering containers pH gallon (healthy, white roots) pH 3.8 in 30 gallon tub (lack of healthy white roots)

What is pH? p= proportion / H = of H + ions p= proportion / H = of H + ions Relative concentration of H + in water Relative concentration of H + in water – H 2 0 H + + OH - – H + and OH - must always be equal in a neutral solution – Water has properties of both a weak acid and a weak base.

Significance of pH Chemical controls (insecticides, fungicides, miticides) Chemical controls (insecticides, fungicides, miticides) Nutrient availability Nutrient availability Root system development Root system development Microbial activity Microbial activity

Significance of pH Chemical controls (insecticides, fungicides and miticides) Chemical controls (insecticides, fungicides and miticides) – Ideal pH range between 5.5 to 6 – Acceptable range is 4 – 7

Insecticides and basic pH of water The effectiveness of some classes of insecticides is greatly reduced when the pH of the water used for dilution is at or over a pH of 8. The effectiveness of some classes of insecticides is greatly reduced when the pH of the water used for dilution is at or over a pH of 8. In these instances, a high temperature also reduces the effectiveness. (Alkaline hydrolysis) In these instances, a high temperature also reduces the effectiveness. (Alkaline hydrolysis)

Insecticides and basic pH of water Most susceptible are: ORGANOPHOSPHATES (malathion) -(and DIMETHOATE, a mitecide), Most susceptible are: ORGANOPHOSPHATES (malathion) -(and DIMETHOATE, a mitecide), CARBAMATE (Sevin), and some PYRETHROIDS. CARBAMATE (Sevin), and some PYRETHROIDS. Fungicides are not sensitive to pH. Fungicides are not sensitive to pH. ≈pH precautions not usually on the label≈

Biologicals and pH A pH over 8 will reduce the effectiveness of BT (Bacillus thuringiensis) A pH over 8 will reduce the effectiveness of BT (Bacillus thuringiensis) Never mix COPPER SULFATE, COPPER OXIDE or BORDEAUX MIXTURE with acidic water…they may produce a phytotoxic effect. Never mix COPPER SULFATE, COPPER OXIDE or BORDEAUX MIXTURE with acidic water…they may produce a phytotoxic effect.

Insecticides/Fungicides and pH

Treat ‘em all alike Rather than try to memorize which insecticides and miticides are sensitive to pH, threat them all with the same precautions until you are certain that they will be unaffected. Rather than try to memorize which insecticides and miticides are sensitive to pH, threat them all with the same precautions until you are certain that they will be unaffected. Using the wrong pH can render the chemical ineffective. Using the wrong pH can render the chemical ineffective.

pH of water to dilute insecticide pH range of 3.5 – 6.0 – Spray – Short term storage of 12 to 24 hours pH range of 6.1 – 7.0 – Spray – Do not leave in leave in sprayer over 2 hours pH above 7 or below 3 – Do not use to mix insecticide

St. Tammany Water pH Municipal Supply pH Madisonville7.3Pam P. Mandeville7.8Kappy Folsom7.9Art Mandeville8.8Julie

Municipal water supplies Why are they all alkaline (above a pH of 7) (Because an acidic pH will dissolve copper pipes over time)

Optimum pH for most crops is 5.5 – 7 Optimum pH for most crops is 5.5 – 7http://soils.missouri.edu As soil pH decreases, availability of nutrients are reduced As soil pH decreases, availability of nutrients are reduced As pH drops below 5.5, population of microbes is reduced As pH drops below 5.5, population of microbes is reduced As pH drops below 5.5 solubility of Al and Mn increases along with their toxicity As pH drops below 5.5 solubility of Al and Mn increases along with their toxicity As pH drops below 5.5, the effect of Al toxicity and greatly reduced availability of Ca contributes to poor root development and plant growth As pH drops below 5.5, the effect of Al toxicity and greatly reduced availability of Ca contributes to poor root development and plant growth

Keep pH 6 – 7.2 – Ideal for plants (But, some prefer a more acid soil like blueberries and azaleas while others like it a little more alkaline.) ( – Optimum pH for most nutrients is 6 – 7 – Most bacteria like pH between 6 – 7.5 – Fungi and actinomyces OK with a pH of 5.5 – 8 (Actinomyces are anaerobic bacteria with fungal like filaments.) – Earthworms do best with pH >6.5 Practical significance of pH

N +/- P + K + S - Ca + Mg + Fe + Mn + Cu + Zn + B + Mo - Al + Primary nutrients Secondary nutrients Micronutrients {Ni + and Cl - are sometimes included} science.uq.edu.au