Find out why we need fertilisers; which nutrients are essential; how nutrients become available to plants; and which nutrients can cause animal health problems if not correctly balanced in the soil.
3.1 Introduction
Plants require nutrients for normal growth. These must be in a form useable by the plants and in concentrations that allow optimum plant growth. Furthermore, the concentrations of the various soluble soil nutrients must be properly balanced.
3.2 Why do we need fertilisers?
Many Australian soils are of low fertility, and improved pasture species require a higher level of soil fertility than do native pastures. Fertilisers are required to overcome the soil’s inherent nutrient deficiencies and to replace the nutrients that are lost or removed through crop and pasture production. Without fertiliser applications soils can become depleted in a dairy farming system.
3.3 The essential plant nutrients
Seventeen nutrients are known to be essential for plant growth. There is also a range of beneficial nutrients, and some elements that are required for animal health but have no known value to plants. A deficiency in any one of the 17 essential nutrients will reduce growth and production, even though the others may be abundantly available. Optimum pasture production can only be obtained if all the requirements for plant growth are met.
3.4 The major nutrients or macronutrients
The macronutrients (nitrogen, phosphorus, potassium, sulphur, calcium and magnesium) are required in relatively large quantities by plants. Plant growth may be retarded if these nutrients are: lacking in the soil, become available too slowly, or are not adequately balanced. Find out the importance of each macronutrient, the deficiency symptoms, and how they cycle in the soil to become plant available. Also find out the animal health implications associated with imbalances of certain macronutrients.
3.5 Minor nutrients or trace elements
Although only required in small amounts, trace elements are essential for plant growth. It is possible to have toxicities of trace elements, as well as deficiencies. Some trace element deficiencies in plants can also cause nutrient deficiencies animals. Find out the role of trace elements, the deficiency symptoms, and the animal health implications associated with imbalances of trace elements in the soil.
3.6 Summary
3.7 References