(IPPM) in Vegetables - Vegetableipmasia.org

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Resource Manual on IPPM in Rice World Education Philippines, Inc. · Minimize disturbance of the soil, which would reduce biological diversity and accelerate the destruction of soil structure and organic matter. H. What is Soil pH The pH of a soil refers literally to the Potential Hydrogen and is a measure of the soil acidity. Technically, pH refers to the amount of hydrogen ion (H+) present in the soil water (or any kind of liquid), measured on a logarithmic mathematical scale. In rice production, knowledge of soil pH, particularly how to measure and manage it, is very important especially since pH affects soil chemistry and plant nutrition. The pH is a scale of measuring acidity that ranges from 0 to 14. A low pH (0-5) is acidic, and a high pH (9-14) is basic (lacking H+). A pH level that ranges from 6 to 8 is considered neutral pH. In many areas of the tropics soils are generally acidic. Some soils have a pH level of as low as 4.0 and some even have as low as 3.0 pH. Soil acidity does not directly hurt the plants, but rather, it affects the availability of nutrients for the plant. The same is also true for soils that are too basic (lacking in H+). 12
Resource Manual on IPPM in Rice World Education Philippines, Inc. To further explain the idea of soil pH, a more general analogy can be used. Imagine the soil as a huge pantry or a place for storing food in the house. The pantry must be a goodenough cabinet, cool enough to maintain the freshness of the food kept in it. Similarly, the soil has to have the good qualities for it to be an appropriate storage place for nutrients. In the case of sandy soil or a soil under high rainfall conditions, the nutrients are often leached or dissolved. Thus, the pantry turns out to be a poor place for storing food. In this case, putting OM back into the soil is just like stocking the pantry with food. An ideal soil with a good mixture of sand, silt, clay and organic matter, therefore, is like a large pantry that allows storage for many kinds of food. If the soil pH is too low or too high, storage of nutrients will be difficult and the pantry will be empty. Thus, to increase soil nutrients, pH level must be maintained at a desirable balance. Improving Acid Soils Lime is the most common material used to neutralize acid soils. Lime in pure form is calcium carbonate (CaCO 3 ). What is important in lime is not the calcium (Ca++), although calcium is a required nutrient for plant growth. Rather, it is the carbonate (CO 3 ) that helps balance the pH level of acid soils. It does this by combining with the hydrogen ion (H+). Each carbonate molecule combines with two hydrogen ions, and in this way the lime cleans up the excess H+ and raises the soil pH toward neutral. The formal description of the reaction goes as follows: 2 CaCO 3 + 3H+ 2Ca++ + HCO 3 - + H 2 CO 3 For every two molecules of CaCO 3 , 3 ions of hydrogen (3H+) are taken up (lowering the pH), producing 2Ca++ (which are now available for storage in the soil, or uptake by the plant), and one molecule each of bicarbonate (H 2 CO 3 ) and HCO 3 -. 13
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Page 3 and 4: Compiled and published by: World Ed
Page 5 and 6: ACKNOWLEDGM ENT World Education (IN
Page 7 and 8: 1. Leaves 48 2. Flower 49 3. Fruit
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