Soil productivity is considered as important factor for the success of agricultural production rather than soil fertility. Status of nutrient present in the soil and its ability to supply the nutrient determines the fertility of the soil whereas the ability of soil to produce the higher yield is soil productivity. Production of agricultural depends upon the many properties of the soil such as its textural class, structure, acidity, alkalinity, water holding capacity, cation/ anionexchange capacity, etc.  (Brady & Weil, 2012). Crops are generally suited for particular textural class of soiland so all fertile soils are not productive. For e.g. potato gives higher production in loamy to sandy loam soil and it is not suited to clay soil even if its fertility is high. Therefore we can say fertile soil is not always productive but productive soil is always fertile.

Soil is a vibrant habitat for huge variety of life-forms. It gives a mechanical support to plants from which they extract nutrients. It shelters many animals from invertebrates such as worms and insects up to mammals like rabbits, moles and badgers. It also provides habitats for microorganisms. All these forms of life interrelate with each other and with the soil to create continually changing conditions. This allows changes in soil fertility and the soil productivity.

Soil contains many micro and macro flora and fauna. According to the study conducted by Johnson in 1979, agricultural field containing 4% organic matter has the following count of soil macro and micro flora and fauna,

(Estimated content of organism in soil, Johanson, 1979)

Similarly the study of Torsvik et al in 2002 showed the similar count of the micro flora and fauna on the surface soil horizon. The rhizosphere, area around the effective root zone, can comprise up to 10¹¹ Microbial cells per gram of root and above 30,000 prokaryotic species in general (Egamberdieva, Kamilova, Validov, Gafurova, Kucharova, & Lugtenberg, 2008). This indicates organic compound have a positive correlation with the microbial population. Soil rich in organic matter has higher count of micro flora and fauna than soil with low organic matter. Forest soil is rich in micro flora and fauna (Mandal, 2013). And soil containing higher number of micro flora and fauna are considered as a living soil.

The agriculturally beneficial microbial populations are plant growth promoting N-fixing cyanobacteria, rhizobacteria, mycorrhiza, plant disease suppressive beneficial bacteria, stress tolerance endophytes and bio-degrading microbes. Count of Azotobacter, Azospirillum, Rhizobium, cyanobacteria, phosphorus and potassium solubilizing microorganisms and mycorrhizae where high under no tillage or minimum tillage soil.  These are some of the plant growth promoting rhizobacteria   (Bhardwaj, Ansari, Sahoo, & Tuteja, 2014). Bacterial are the important soil microorganism responsible for many enzymatic transformation like nitrification, ammonification etc. Azosprillum is micro aerobic that fixesthe nitrogen in association with roots of grasses. Inoculation of Azosprillumto the grass crops have positive hormonal effect on roots and plant growth (Mandal, 2013). Rhizobium alonein symbiotic association with legume fixes about 50-200 kg of N₂ per ha. The following table shows the amount of nitrogen fixed by the different microorganism with symbiotic association with different species of plant.