All MDS suggest that the best indicator of soil quality is the percentage of organic matter. Now, to the question, fertility is made up of many variables, some can be as simple as adding Urea, others more difficult such as reducing the salinity of the soil (electrical conductivity). Microorganisms consume organic matter, a process known as mineralization, making two functions available: the first is the release of molecules such as ammonium, etc., and the second is forming a molecule with surfaces capable of exchanging cations along with the retention of available moisture. If there is a lot of organic matter available, the more organisms the better fertility, but if there is little organic matter, the number of organisms will adapt, reducing to eventually senescence.

There are many ways to add organic matter or increase the amount of organic matter. It's all in whether it's conventional or organic, the time and resources available.

Fertilizers such as nitrogen, potassium and phosphorus are added to the soil to make it fertile. These are also added to the potted plants in gardens to enhance plant growth. NPK and urea are the most common fertilizers required by the soil. Urea adds nitrogen to the soil. Such soil fertility management practices include the use of fertilizers, organic inputs, crop rotation with legumes and the use of improved germplasm, combined with the knowledge on how to adapt these practices to local conditions. The amounts of nutrients that become available to the plants depend on the time of year the manure is applied and how quickly it is worked into the soil. Granular or pelleted material such as commercially available manures, blood and bone with rock dust supplement or specially formulated pellets are best if you want sustained fertility. If your plants really need a quick lift then liquid fertilizers are the go. The main effects of the presence of microorganisms in the soil are: Improved plant nutrition. Microorganisms increase the source of nitrogen in the soil, or they can supply it directly to the plant, as they have the ability to take and set nitrogen from the atmosphere. Microorganisms are essential to soil formation and soil ecology because they control the flux of nutrients to plants promote nitrogen fixation, and promote soil detoxification of inorganic and naturally occurring organic pollutants. They increase soil fertility by incorporating air, minerals and nitrogenous compounds. They contribute in increasing plant growth by providing essential elements, minerals that plants cannot utilize by their Owen. Microorganisms decompose organic matter to simpler form that can be easily uptake by plants. Soil fertility can be further improved by incorporating cover crops that add organic matter to the soil, which leads to improved soil structure and promotes a healthy, fertile soil; by using green manure or growing legumes to fix nitrogen from the air through the process of biological nitrogen fixation.Crop rotation, fertilization, mixed planting, sowing green manure, mulching, and fallowing help to increase field fertility. The impact of living organisms on farmland fertility is also hard to overestimate: earthworms, beneficial fungi, bacteria, and protozoan unicellular organisms are extremely helpful to the soil.