Organic or Chemical Fertilisers?

Fertiliser is an essential tool in the modern farmer’s armoury. Fertiliser enhances the growth of plants in one of two ways — through adding nutrients, and through making soil more effective by improving its ability to retain water and making the soil more aerated. Farmers can distribute fertiliser by using mechanised spreading equipment.

Improvements in fertilisers have been an essential component of increased crop yields over the course of the last century. Without fertilisers, it is unlikely that agriculture would have been able to keep feeding the earth’s rapidly increased population.

But fertilisers are not without their drawbacks. Overuse can lead to issues such as fertiliser burn, in which the affected crops show signs of browning on their leaves. Improper use of fertilisers can also have an adverse effect on the quality of topsoil, leading to a drop in soil quality down the line. In particular, microorganisms that aid in plant growth can be harmed by inappropriate fertiliser use. Chemical fertilisers have consequences outside of the bounds of your farm — many are produced from non-sustainable sources, such as oil by-products and mining.

This can lead farmers to a choice between chemical and organic fertilisers. What are the advantages and disadvantages for each fertiliser type?

Chemical fertilisers

Common types of chemical fertilisers include ammonium sulphate, ammonium phosphate, ammonium nitrate, urea, and ammonium chloride. These are artificially prepared from synthetic materials. Chemical fertilisers are rich equally in three essential nutrients that are needed for crop growth, phosphorus, nitrogen and potassium. Chemical fertilisers allow you to immediate supply these nutrients to your plants if needed. Chemical fertilisers pack more nutrients in than organic fertilisers, which means that they can be cheaper to purchase than their organic counterparts. Chemical fertilisers give farmers the option of releasing nutrients quickly or slowly.

However, chemical fertilisers can be hazardous. Many chemical fertilisers are highly acidic. This can result in chemical burns, if they are not handled correctly, and can change your soil’s fertility when used intensively over the course of a few seasons.

Organic fertilisers

Common types of organic fertilisers include cottonseed meal, blood meal, fish emulsion, and manure and sewage sludge. Organic fertilisers are derived from living things, and are typically untreated or only slightly treated. Organic fertilisers add nutrients to your soil naturally, and increase your soil’s organic matter concentration. This improves soil structure and tilth, water holding capacity, while reducing crusting problems, erosion from wind and water. Organic fertilisers provide a slow and consistent release of nutrients, which can be both a blessing and a curse — if you need to stage a quick intervention on your crops, organic fertilisers will not be as effective as chemical fertilisers.

Organic fertilisers can also be hazardous — organic waste can contain harmful bacteria, and should be handled with care. Since nutrients are less concentrated than in chemical fertilisers, organic fertilisers can end up being more expensive. The advantage of organic fertilisers is that you can prepare them yourself with a little preparation. Using techniques like cover crops can provide topsoil friendly fertilisation.