- March 20, 2018
- By Mike
- In Lawns, Soil
I thought i would briefly look at fertilizer applications with high salt indices and the affect on microbiology and why i try to reduce salt indices. Its a subject of choice many lawn companies may not pay any mind to but may help you better understand why we do what we do.
Salts are soluble compounds formed from ions charged as atom or molecule. When we talk about salt i am referring to NaCI or sodium chloride table salt and sea water.
Salt is an ionic compound formed of a single sodium ion. There are many forms of salt that occur naturally but also form from man made production. In terms of fertilizer salt is a large part of most man made fertilzers.
Soils have a saline level which refers to the amount of salt in them they can become more saline from sea water and sea air deposits or from contamination from other input such as irrigation and fertilization.
Salt and Microbiota
So when we apply a fertilizer the elements (compounds) are bound together and release when wet. As they release they are absorbed via a process called osmosis where they pass through the semi permeable cell membrane into the plant. This can also happen in reverse when too much fertilizer is applied and effectively draw out the cell solution of the plant to the external fertilizer which leads to scorching. The microbiota being a cellular organism can suffer the same fate when in a high saline solution which inevitably will lead to them perishing.
Some soil microbes have a high tolerance to salinity this they do by accumulating osmolytes in thier cells osmolites are organic molecules such as amino acids or carbohydrates that counteract osmotic pressure. For the microbial life to synthesise these osmolytes requires substantial energy and adenosine triphosphate. So unless existing microbial populations have available sources of amino acids or carbohydrates chances are when applying high salt based fertilizers we will see a decrease in the microbial populations and their ability to recycle nutrients leading to increases in thatch.
Soil organic matter is a major part of soil by keeping the microbiota that live in the soil in balance we see a decrease in detritus and an increase in Humus. Humus is produced by the microbial life as they break down the detritus during the process of mineralization which is decomposition of the organic matter into simple compounds. During this process they create humic and fulvic acid (amino acids) which will ultimately increase their ability to withstand salt applications.
Certain arbuscular mychorizal fungi (AMF) that promote root development can aid against salinity when low water content is available (low matric pressure) and are much more tollerant than bacteria in low moisture conditions. If these populations are low they can be boosted when over seeding with a seed innoculant after scarifying.
At heritage as your probably guessing we try to reduce our salt input and increase our bio stimulants that boost both the fungi and bacteria. But as your guessing water and soil type also play as big part. Sandy soils are able to leach salinity but they will also leach nutrients which will lead to a drop in carbon and nitrogen cycling by the microbial communities. Soils with a higher CEC (cation exchange capacity) value such as clay and organic soils tend to better buffer saline levels due to the higher number of exchange sites that can absorb mineral ions which effectively remove them from the solution.
Cost vs Quality
You really get what you pay for with a lawn treatment. If your lawns tired and your considering lawn care give us a call and see what our program can do for you.