Fertilizers that usually contain one nutrient which can be used directly by plants are commonly called

The fertilizers that usually contain one nutrient which can be used directly by plants are commonly called straight fertilizers. Straight fertilizers are generally composed of a single nutrient, such as nitrogen, phosphorus, or potassium, and are used to supplement specific nutrient deficiencies in soil. They are typically applied in their pure form, without any additional additives or fillers, making it easier to precisely control the amount and type of nutrient being added to the soil. Straight fertilizers can be either organic or inorganic, and are often used in combination with other fertilizers or soil amendments to create a nutrient-rich growing environment for plants.