**2. General overview of agricultural intensification**

As a result of an increase in global population, food and nutrition insecurity is expected to increase especially in developing countries due to a decline in arable land per capita [5]. However, the production of food for human consumption, animal feed, and industrial purposes has increased in developed countries mainly because of an increase in crop yield and cropping intensity rather than because of an expansion of arable land [6].

#### **2.1 Intensification in agriculture and sustainability**

The rapid growth of the global population, currently at 8.045 billion, necessitates fiber and food production to be increased without increasing the land for agricultural activities [7]. The phenomenal growth in the global production of food since the mid-1960s has not seen a matching significant improvement in food and nutrition security. The recent Covid-19 pandemic has made things worse. For example, world hunger increased in 2020 due to the COVID-19 pandemic, while undernourishment increased by 1.5% in 2020, with 218 and 418 million of these cases residing in Africa and Asia, respectively [8]. More than a third of the world's population did not have access to adequate food in 2020; 12% were severely food-insecure [9]. The uneven spread of economic wealth between the developing and developed nations of the world arising from modern production systems, which consequently lead to the overlooking of social equity and environmental sustainability, is one of the contributing factors to the aforementioned food insecurity [10]. Increased food production is not sustainable because of environmental, socioeconomic, and financial inefficiencies in the world

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

[10]. But currently, statistics indicate that sugarcane, wheat, rice, and maize account for nearly half of the global crop production, and this amounted to 9.4 billion tons in 2019 [11]. In 2021, tomatoes (189.13 MMT), onions (106.59 MMT), cucumbers (93.53 MMT), cabbages and other brassicas (71.71 MMT), and eggplants (58.65 MMT) were the top five most produced crops in the world [12]. In general, China, the United States, Brazil, India, Russia, France, Mexico, Japan, Germany, and Turkey are the top ten agriculture-producing countries in the world. Be that as it may be, one school of thought proposes that the issue of food and nutrition insecurity is heavily linked to food losses along the value chain [13]. According to these authors, about a third of the world's food is lost and therefore does not reach the consumer's table.

#### **2.2 Agricultural production in Africa**

Incessant droughts emanating from the *El Nino* weather phenomenon, pests and diseases, and low soil nutritional contents, among others, are leading to low crop yields in Africa [1]. But, the use of agrochemicals, high-yielding cultivars, and mineral fertilizers is part of a wider scale of intensive agricultural production system programs that are being implemented to increase production and yield [14]. However, this attempted intensification of agriculture is leading to a massive decline in soil health and fertility, among others, more so in Africa [15]. The main causes of poor soil fertility in Africa include leaching, improper application of mineral fertilizers, soil erosion, low organic manure amendments, and the removal of crop residues, among others [16]. Africa constitutes 60% of the world's arable land and drives most economies by employing most people, consequently contributing about 14% of sub-Saharan Africa's GDP [17]. Africa therefore poses great potential in terms of crop production and yield in the face of droughts. Although the overuse of both organic and inorganic fertilizers has been linked to environmental degradation among other factors, the underapplication of these, harsh climatic conditions, as well as poor soil management and agricultural practices have led to soil degradation in most parts of SSA. This leads to a decline in yields and consequently food and nutrition insecurity in the region. However, Africa produces corn, wheat, and rice in this order, while corn has the widest use and is grown in all ecological zones [18]. The highest yields of corn have been reported in Egypt, Reunion, and Mauritius, while millet and sorghum are cultivated in the dry regions of the Savanna. The cultivation and consumption of rice are on the increase owing to rapid urbanization. In addition, fodder crops are mainly restricted to East and Southern Africa's highland zones as well as North Africa's subtropical zones [18].

#### **2.3 Constraints of intensifying agriculture in Africa**

The use of mineral fertilizers has been adopted at a global scale because they significantly increase yields; however, in Africa, their use is limited because of high costs [19]. Most farmers are subsistence-oriented and constitute about 80% of food producers in the region [2]. Consequently, these farmers are unable to purchase highly priced mineral fertilizers. Research has also shown that 64–70% of SSA farmers are unable to adopt alternative soil management techniques because of financial challenges [20].

#### **2.4 Sustainable agricultural production**

One of the most critical aspects of alternative soil management practices and studies is sustainability. Sustainability is seen as the ability of farming systems to persist into the future [21]. According to the previous authors, this means that sustainable agriculture is the ability to ensure that farming systems continuously adapt to new and improved strategies while enabling future food demands to be met for posterity. Social, economic, and environmental aspects are some of the many multidimensional characteristics of sustainable agriculture [22]. Because of its positive environmental, economic, and social roles, organic farming is being promoted and consequently expanding rapidly around the world [23]. Soil microbial pools are the pillar of agricultural production in organic systems, more so in nutrient supply [24]. Thus, organic farming has been on the increase over the last few decades at about ca. 20% annually and covering over 24 million hectares around the world [25, 26]. Consequently, organic farming has been adopted as the mainstream practice for some crops [23].

Organic farming lessens environmental stress [27], improves soil biodiversity [28], and enhances the formation of soil structure while improving food safety and quality [29]. The use of biological and organic inputs for pest and disease control as well as nutrient supply are the main drivers of organic farming [30]. Sustainable organic farming depends largely on the build-up of soil microbial pools that serve as a temporary nutrient sink and are accountable for releasing nutrients from organic matter for plant use [23]. Reports indicate that microbial biomass nitrogen contributes to the primary nitrogen source of potentially mineralizable soil nitrogen [31]. Thus, EM ensures maximum returns of soil microbial pools.

### **3. Effective microorganisms**

According to Safwat and Matta [3], EM are essentially a combination of microorganisms that are beneficial to the soil for health. Predominant species of LAB, a small population of photosynthetic bacteria, yeasts and actinomycetes, among others, constitute EM. To co-exist in an aqueous culture, these microorganisms need to be mutually companionable. Some EM include the following:

#### **3.1 Lactic acid bacteria**

Lactic acid is produced by LAB from sugars and carbohydrates that are developed by some yeasts and photosynthetic bacteria. Some of the foods that have been produced for decades using LAB include pickles and yoghurt. Because lactic acid is a strong sterilizing compound, it can enhance organic matter decomposition and suppress harmful microorganisms. Lignin and cellulose are some of the materials whose decomposition is promoted by LAB, followed by fermentation, and this process consequently removes undesirable effects of non-decomposed organic matter [32].

#### **3.2 Yeasts**

Plant roots, organic matter, and photosynthetic bacteria secrete sugars and amino acids, which are further synthesized into antimicrobials and some beneficial substances that are required for plant growth. Root and active cell division are thus promoted by hormones and enzymes, which are some bioactive compounds, that are produced by the yeasts. These secretions act as useful substrates for effective microbes such as actinomycetes and LAB [33].
