There are three classes of nutrients--primary nutrients, secondary nutrients, and micronutrients. These classes are determined by the amounts and importance of the nutrients that are required by an organism. Primary, or essential nutrients, are irreplaceable elements; that is to say there is no substitute for them for the completion of a normal life cycle. The required amount of secondary nutrients is less than that of primary nutrients. Micronutrients are only required in extremely small, or trace, amounts. Before planting a crop, a farmer must test the soil in the field and determine how much of each nutrient is available to plants. If the soil is lacking important nutrients, then they need to be supplemented. This is similar to the human practice of taking vitamins. Nutrients are often supplied to crops by the farmer in the form of fertilizer, as seen in the photograph above. Photo: Liquid fertilizer being applied to a field of wheat. Photo courtesy of Wheat Mania.
The following are some important wheat nutrients and the conditions in which they are used:
Phosphorus (P): Phosphorus is applied before the wheat is planted. The amount applied depends on the amount of phosphorus already in the soil.
Potassium (K): Like phosphorus, potassium is applied before the wheat is planted, and the amount applied depends on the amount of potassium already in the soil.
Sulfur (S): The amount of sulfur needed by wheat depends on the amount of nitrogen available to the crop. The ratio of nitrogen to sulfur should be 15:1. When the amount of nitrogen in the plant is greater than the 15:1, sulfur-containing fertilizer is added.
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