To Be Or Not To Be “Organic”.

Plant nutrients are sourced from either synthetic fertilisers or organic materials. But which is the best choice for your landscape design project? Both forms have their merits and if used correctly and in the right situation can optimise your garden and plant growth.

As listed in Table 1 there are both benefits and limitations. So, which is the best option for you? Generally, I would recommend using both but to properly answer that question its best to look at the landscape you’re constructing or maintaining and its requirements.

Standard synthetic fertilisers are beneficial in the following situations:

·       Newly constructed urban landscapes where rapid growth is essential.   

·       Established gardens or landscapes where plants are underperforming.

·       Turf grass such as amenity areas, parks ovals and sportsfields.

Slow-release synthetic fertilisers are recommended in the following situations:

·       A low dose of a slow-release fertiliser is recommended for newly constructed bioretention basins or wetlands. Avoid the use of a standard fertiliser or organics as this will promote algal blooms.

·       Porous media such as in potting mixes and green roof blends to prevent nutrient leaching.

Organic fertilisers are beneficial in the following situations:

·       All landscapes (except turf and aquatic landscapes) where organic matter levels are less than 3% w/w. Soil testing is required to determine the organic matter level.  

·       To restore physically damaged soil.

·       To promote soil health.

Getting the fertiliser type and application rate right is critical to avoid toxicity. Not only is over application of fertilisers a waste of your money but it has detrimental environmental effects.  Over application of organics results in slumpage as the organics decompose, oxygen levels diminish leading to plant failure. Therefore, soil testing is always recommended as part of the landscape construction and maintenance process to properly understand what your soil needs to promote plant growth and to avoid any undesirable outcomes.

Contact your local Urban Soil Doctor for more information.