Healthy growth for your lawn requires relatively small amounts of nitrogen (N), phosphate (P) and potash (K). Applying too much nitrogen can cause lush growth. Lush growth produces excessive leaf material that is susceptible to disease. Another problem with rapid growth is that the grass will need cutting more frequently. A lawn fertiliser needs to be low in nitrogen. “Growmore” is just 7% N and is balanced with 7% P & & 7%K. P sustains root growth and K helps to keep the turf free of disease.
A chemical / mineral blend of NP&K often contains no trace elements or nourishment for beneficial organisms that can thrive in the soil. Organic fertilisers feed your lawn above the ground and improve the root zone below it. Chemical fertilisers can be cheaper because they are produced in vast quantities. They are easy to apply and provide a rapid growth response. When we encourage a lawn to grow with a fertiliser that contains only NP&K we rely on a bank of trace elements within the soil. Trace elements such as manganese (Mn), magnesium (Mg), molybdenum (Mo) and boron (B) to name a few are used by growing grass. They provide the building blocks for individual cells within a plant. Nutrient deficiencies lead to disease and chlorosis (yellow plants.)
Organic fertilisers provide your lawn: a full suite of trace elements, a food source for micro-organisms together with NP&K. Following application beneficial bacteria multiply in response. Vast numbers of microscopic organisms can feed on organic material in the root zone and their excretion is soluble plant food. A dressing of organic fertiliser is not easily leached away and the plant nutrients are made available slowly via beneficial bacteria.
From an environmental point of view; the reaction to extract nitrogen from natural gas (the Haber- Bosch process) takes place at 450° Centigrade and under 200 atmospheres of pressure. This is fuel hungry. On their website The Organic Research Centre states that four to six tonnes of crude oil are required to produce one tonne of chemical fertiliser. Organic fertilisers are a by-product. For example blood, fish and bone is mixed from waste of the food industry; a sustainable alternative to manufactured chemicals because the raw materials already exist.
Six weeks after application of a standard NPK compound fertiliser the nitrogen and potash will have leached away while P (phosphate) levels in the soil can increase and become problematic as this substance is less soluble. True fertility to promote healthy growth depends on healthy soil, beneficial micro-organisms, trace elements and then major nutrients provided in a balanced feed.