Explain Why Lime & Ammonium Fertilizer Should Not Be Added at the Same Time

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Fertilisers that contain lime and fertilisers that contain ammonium are both designed to change the pH of soil, but in different directions. Although adding fertiliser to the soil is important for the health of a number of plants, using the right types of fertiliser at the right time of year is equally important.

Soil pH

Soil pH is affected by lime and ammonium or ammonium sulphate. The pH scale ranges from 0 to 14. A measurement of 0 to 7 is an acidic soil, while 7 to 14 is alkaline. Adding fertiliser helps gardeners balance the pH of the soil and keep it at a healthy level for plants. Many plants prefer a mildly acidic soil. Raising or lowering the pH of the soil depends on the type of fertiliser and the initial soil pH.

Lime and Ammonium

Lime, often derived from limestone, is used to increase the pH of the soil and make it more alkaline, according to the Clemson Cooperative Extension. Fertilizers that contain lime are used in situations where the soil is too acidic for the health of plants. Ammonium and ammonium sulphate fertilisers decrease the pH of the soil and make it more acidic. Adding ammonium to the soil helps make it healthier for plants that need an acidic soil for growth.

Adding Fertilizers

The pH of the soil is affected by the type of fertiliser added. However, adding fertilisers that contain both lime and ammonium has an undesired effect on the soil. Equal amounts of lime and ammonium may balance out, leaving the pH of the soil unchanged. A slightly unbalanced amount of lime or ammonium leads to a pH that is not acidic or alkaline enough, depending on the needs of the soil and the plants growing in the garden.

Fertiliser Burn

Another problem associated with adding lime and ammonium fertilisers at the same time is fertiliser burn, which results from the application of excess fertilisers. Salts and other chemicals in fertiliser dry out the soil and the plants they are placed on, which gives grass, trees, shrubs and flowers a dried-out and burnt appearance. Heavy and simultaneous applications of these two types of fertilisers do more harm than good to the garden. Avoid adding too much fertiliser to the soil.