*3.7.1 Effects of EM on organic matter*

Soil biological, chemical, and physical characteristics can be improved by the addition of organic manures in addition to the supply of multiple nutrients. Farmers prefer mineral fertilizers in comparison with organic options because mineral fertilizers are quickly released and become available to the plant almost immediately. Organic fertilizers, on the other hand, are slowly released over a long period, and this may not quickly lead to increased yield. The release of nutrients to plants is thought to be stimulated by combining organic manures with EM. The improvement of soil and crop quality after inoculating agro-systems with EM has been shown [46]. The

#### *Effective Microorganisms (EM): A Potential Pathway for Enhancing Soil Quality… DOI: http://dx.doi.org/10.5772/intechopen.114089*

rapid growth of the plant results from the rapid mineralization of organic materials following EM application into the soil. This is because there is a rapid increase in beneficial microorganisms that consequently aid plant growth [3]. The application of EM or organic materials alone has not been shown to significantly increase yield [47]. However, their integrated use resulted in a 44% increase in yield over the control. Application of EM with mineral fertilizer in this case resulted in a slight increase in yield (14%) over the mineral fertilizer alone, demonstrating that EM is more effective when applied with organic manures. EM is comprised of various microbes that respond well when sufficient organic matter is available. This is why mineral fertilizers exhibited a slower release in comparison to EM. Yaseen et al. [48] revealed that arbuscular mycorrhizal and Rhizobia and inoculation of bean plants significantly increased pod yield in organic matter-supplemented plots compared to those treated with synthetic fertilizers. The impact of combining organic matter and EM was shown through a 38% increase in nitrogen leaf composition in comparison to the 16% observed in organic matter application alone [47]. Rapid mineral nutrient release into the soil for exploitation by plants is enhanced by EM through determination and stimulation of mineralization of organic materials [46]. In tomatoes, a higher phosphorus composition, 50 days after transplanting, was observed following the application of EM [49]. But, 90 days post-transplanting tomatoes, P and N contents were low in soils treated with EM, and this was potentially because of nutrients being absorbed by plants that showed faster growth and consequently higher yields. The release of P and N from organic matter-amended soils over an incubation period of 21 days at 60°C has been previously studied, and it was shown that the addition of EM increased both P and N in comparison to the control [50].

#### *3.7.2 Effects of EM on the photosynthetic capacity of crops*

The effects of combining EM with bokash on yield, photosynthesis, and plant growth in comparison with mineral fertilizers have been studied [51]. Dry matter yields during early growth phases but lower during later phases were observed by these authors but in mineral fertilizer-treated plants compared to EM plants. Vigorous growth, elevated photosynthesis, and increased root mass and activity throughout all growth stages were observed in EM and bokash-treated plants compared to mineral fertilizer-treated plants. Bokash-EM-treated plants lead to well-developed roots, and these are essential in maintaining increased photosynthetic activities and growth rates [52]. EM mineralizes nutrients from bokash and therefore ensures sustained availability of nutrients and consequently higher plant growth rates [53]. Senescence delay and root activity stimulation are potentially stimulated by growth regulators in EM [52]. Plant growth regulators such as abscisic acid, auxins, and gibberellins play a critical role in the development and growth of plant roots [54]. Metabolism and plant growth can be enhanced by some bioactive compounds that are produced by actinomycetes, fungi, and/or bacteria [51]. However, the stimulation of plant metabolic processes and growth by EM is not yet fully understood. However, the ability of EM to biosynthesize antioxidants is thought to be responsible for these microbes' beneficial effects [3].

#### *3.7.3 Effects of EM on crop yield*

Soil-borne pathogen suppression, an increase in plant nutrients, and an increase in yield are all enhanced by the application of EM [3]. First-grade sweet corn, peas, and onions are enhanced by the application of EM and molasses [3].
