Which fertiliser?

Should you use organic or inorganic fertilisers?

Sometimes advice from garden experts seems to be at best confusing and at worst contradictory. For example, many garden advisers only advocate 'organic' fertilisers, while others don't use this term. What do they mean, and what is an organic fertiliser?

Well, definitions can be as vague as some of the advice but, generally, an organic fertiliser is said to be one that is derived from living material or from a natural source. This includes animal manure and blood and bone.

Organic Fertilisers

From the plant's point of view it doesn't really matter whether its source of nitrogen and other nutrients is organic or manufactured, but if the idea of using an organic plant food is  appealing, the easiest way to do so is by buying and applying some blood and bone or sheep pellets.

Yates Nature's Way Organic Sheep Pellets, for example, are made from pelletised sheep manure and wool waste. As well as being a gentle source of nutrients, the pellets make an excellent soil conditioner. They improve moisture retention and, like most other organic matter, they help to aerate the soil.

The nutrient release from pellets is relatively slow because sustained microbial activity is required to break down the organic matter. This slow release means that the pellets continue feeding plants over a long period and there is almost no risk of the plants suffering from fertiliser burn.

The other really popular organic fertiliser is blood and bone. Blood and bone is made from waste material and is a gentle source of nitrogen, phosphorus and calcium. It doesn't, however, contain any potassium (which is one of the most important plant nutrients) so, if you're using it to feed vegetables, it's a good idea to add some extra sulphate of potash (approximately one part of sulphate of potash to ten parts of blood and bone).

Inorganic Fertilisers

Plants, just like us, get bored if they're given the same food all the time, so, for optimum plant health, it's best to vary their diets by including some inorganic fertilisers.

A fertiliser such as Thrive Soluble All Purpose is dissolved and applied in liquid form and, as a result, it promotes a very rapid growth response. Thus, it's a particularly appropriate choice for fast-growing plants such as flower and vegetable seedlings.

Granular plant foods are concentrated dry fertilisers that have been specially formulated for different plant groups such as roses, citrus and camellias and azaleas. Granules should always be applied to moist soil and watered in well immediately afterwards. They can supply plants with a customised diet.

There's no real answer to what's the best type of fertiliser. For plants, just as for people, variety is the spice of life. The real clue is to select a trusted brand of fertiliser so you can be sure you're getting the very best quality for your plants.

Reproduced with permission from NZOOM Home and Garden content, from the previous website of  The views expressed here are not necessarily those of the RNZIH   HOME AND GARDEN   Top of page

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