How should acidic and basic soil be treated for better yielding crops. Explain your
answer using a flowchart.
Answers
Soil acidity is rapidly becoming a problem in our region. Each year more soil samples handled by the Noble Research Institute have or are prone to acidity problems. Acidic soils create production problems by limiting the availability of some essential plant nutrients and increasing that of the soil solution's toxic elements, such as aluminum and manganese, the major cause of poor crop performance and failure in acidic soils. Below soil pH 5.5 (pH is the measurement of soil aciditythe lower the pH, the higher the soil acidity), aluminum may be concentrated enough to limit or stop root development. As a result, plants cannot absorb water and nutrients, are stunted, and exhibit nutrient deficiency symptoms (especially those for phosphorus). Toxic levels of manganese interfere with normal growth processes in the aerial plant parts, which stunts the plant, discolors it, and causes poor yields.
WHAT CAUSES SOIL ACIDITY?
Producers commonly ask this question of staff soil fertility and crops specialists. There are four major reasons for soils to become acidic: rainfall and leaching, acidic parent material, organic matter decay, and harvest of high-yielding crops. Wet climates have a greater potential for acidic soils. In time, excessive rainfall leaches the soil profile's basic elements (calcium, magnesium, sodium, and potassium) that prevent soil acidity. Soils that develop from weathered granite are likely to be more acidic than those developed from shale or limestone. Organic matter decay produces hydrogen ions (H+), which are responsible for acidity (an ion is a positively or negatively charged element). Like that from rainfall, acidic soil development from decaying organic matter is insignificant in the short term. Harvest of high-yielding crops plays the most significant role in increasing soil acidity. During growth, crops absorb basic elements such as calcium, magnesium, and potassium to satisfy their nutritional requirements. As crop yields increase, more of these limelike nutrients are removed from the field. Compared to the leaf and stem portions of the plant, grain contains minute amounts of these basic nutrients. Therefore, harvesting high-yielding forages such as bermudagrass and alfalfa affects soil acidity more than harvesting grain does.
Nitrogen fertilizer has been blamed for the increase in soil acidity problems throughout the region. Yes, when ammoniacal fertilizer materials are applied to the soil, acidity is produced, but the form of nitrogen removed by the crop is similar to that found in fertilizer. In reality, nitrogen fertilizer increases soil acidity by increasing crop yields, thereby increasing the amount of basic elements being removed.
HOW IS SOIL ACIDITY CORRECTED?
Soil acidity can be corrected easily by liming the soil, or adding basic materials to neutralize the acid present. The most commonly used liming material is agricultural limestone, the most economical and relatively easy to manage source. The limestone is not very water-soluble, making it easy to handle. Lime or calcium carbonate's reaction with an acidic soil is described in figure 1, which shows acidity (H) on the surface of the soil particles. As lime dissolves in the soil, calcium (Ca) moves to the surface of soil particles, replacing the acidity. The acidity reacts with the carbonate (CO3) to form carbon dioxide (CO2) and water (H2O). The result is a soil that is less acidic (has a higher pH).
Figure 1.
HOW MUCH LIME IS NEEDED?
Although harvested crops remove copious limelike elements each year, the soil pH does not change much from year to year, meaning the soil is buffered, or resistant to change.
The most important source of buffering in an acidic soil is the exchange of the limelike elementsmostly calciumattached to the surface of soil particles. As the crop removes these elements from the soil solution, attached elements move from the soil