Glossary of Terms

pH: has a major impact on nutrient availability and the effectiveness of applied fertiliser. High or low pH, i.e. above 7.5 or below 5.5, can indicate that various elements will be insoluble and not available to plants for immediate uptake.

EC: Electrical Conductivity is basically a relative measure of soluble salts in the soil solution. The application of gypsum or fertiliser can raise the conductivity significantly. Where gypsum or fertiliser has not been applied, a high conductivity usually signifies high chloride and sodium. EC should thus be interpreted in conjunction with nutrient levels.

Nitrate: The nitrate measured is a water extract and reflects the available nitrate nitrogen and not the total soil nitrogen. The cropping history and organic matter should be taken into account in assessing the total amount of nitrogen expected to be released through the crop cycle. Levels are a guide to basal dressings and losses due to leaching and volatilisation are generally considered when calculating side dressings and follow up fertiliser. Sap analysis is a useful guide when planning ongoing fertiliser programs.

Phosphorous: Available phosphorous is normally determined from acid extracts where pH is below 7.0 and bicarbonate extracts if pH is above 7.0. Many vegetable crops will respond to applied phosphorous even when "adequate" levels are detected from soil testing. pH is taken into account when recommending phosphorous as the acidity has a marked effect on phosphorous availability. Basal rates of phosphate are a guide, and are set from commercial experience, and from responses measured by sap analysis. Phosphate is important in the early stages of growth for root development and flower initiation. Excessive rates of P can cause zinc, calcium and manganese to be less available.

Ca, K, Mg, Na: Recommendations for soil ameliorants such as lime, dolomite, gypsum and other products are based on soil test levels of the major cations - calcium, potassium, magnesium and sodium.

Cation Ratios: The cations can compete for uptake by plants, and, if a major imbalance of these elements is present, particular deficiencies can occur in the plant even if that element is present in amounts that have been thought to be adequate. Balancing of these major cations, calcium, magnesium, sodium and potassium is therefore an important part of soil nutrient management.

Trace Element: Tests are conducted using various extraction methods and give an indication as to high or low levels available in the soil. These levels are used in conjunction with the pH and soil type information supplied. Follow up petiole analyses will determine whether uptake of that nutrient has been achieved. In many crops soil applications of trace elements must be made prior to planting and therefore, often the soil test and soil type are the only available means to make a decision on pre plant or early foliar trace element applications.