Open access peer-reviewed chapter
Abstract
There has been a rise in campaigns promoting the protection of the environment and the development of green economies. A green economy aims to improve human well-being and social equity while reducing environmental risks and scarcities. It focuses on low carbon emissions, efficient resource usage, and inclusivity. The concept of green economies emerged due to the negative impact of traditional economies on the environment and natural resources. African economies, which largely rely on agriculture, often resort to high-yield crops and chemical fertilizers to meet food demand. However, these practices are costly for smallholder farmers and contribute to environmental degradation. To address this, alternative systems, such as Effective Microorganisms (EM), are being explored. EM are beneficial microorganisms that can enhance crop growth and soil quality. They consist of lactic acid bacteria, photosynthetic bacteria, yeasts, and actinomycetes. Commercially produced EM have shown promising results in enhancing crop growth. However, further research is needed to fully understand their benefits. EM offer a potential solution for organic soil management without harming the environment and are relatively affordable compared to intensive agriculture practices. Therefore, this chapter offers an in-depth focus on EM and their benefits, and potential role in agricultural food production and prospects.
Keywords
- effective microorganisms
- soil management
- mineral fertilizers
- organic manure
- sustainable agriculture
1. Introduction
Some of the strategies that can be employed to intensify agricultural output include planting high-yielding varieties, the use of synthetic crop protection agricultural chemicals, and the application of synthetic mineral fertilizers. For example, about 50% of increased agricultural production has been heavily linked to the use of synthetic mineral fertilizers [1]. This approach is, however, increasingly becoming unsustainable as it causes soil degradation, and the cost of required inputs is often beyond the financial reach of communal farmers. These communal farmers constitute more than 80% of food producers in developing nations [2].
Alternative systems that are more suitable to sub-tropical and tropical smallholder farmers are the target. EM are thus an alternative for crop growth enhancement. EM are cultured, naturally occurring specially selected microorganisms that are beneficial to soil health with the potential to significantly improve plant growth and soil quality [3]. These organisms are made up of selected species, including predominant populations of lactic acid bacteria, yeasts, a small number of photosynthetic bacteria, and actinomycetes, among others. These microorganisms need to be mutually compatible with one another to coexist in a liquid culture.
Prof Teruo Higa from the University of the Ryukyus, Okinawa, Japan, was the first individual to develop the concept of EM in 1971. The improvement of crop quality, growth, yield, soil quality, and health after the inoculation of plant ecosystem or the soil with EM has been widely reported [4]. The application of the microorganisms has been shown to increase sweet potato, peas, and onion yield by 23, 29, and 31%, respectively [3]. Local microbial isolates are being used to produce different brands of EM in over 40 countries around the world. Several South African countries are now producing and marketing EM products including EMROSA (Pty) Ltd., EMLife, and Efficient Microbes among others. Although several companies now market EM products, their use is not yet widespread, but over the years, some commercial farmers have adopted them with positive results. As such, there is an increase in EM use. However, there is a lack of rigorous research on the usefulness of EM in crop production in South Africa, and Africa in general.
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 [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
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 multi-dimensional 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].
3.3 Photosynthetic bacteria
Phototropic or photosynthetic bacteria are a group of self-supporting and independent microorganisms. By using soil heat and sunlight as a source of energy, these bacteria synthesize beneficial substances from harmful gases such as hydrogen sulphide and/or organic matter and root secretions. Plant development and growth-promoting substances such as nucleic acids, amino acids, sugars, and bioactive substances are all developed by these microbes. According to Prescott et al. [33], the metabolites developed by these microbes are absorbed directly into plants and act as substrates for increasing useful populations.
3.4 Actinomycetes
Actinomycetes are microbes that constitute EM, and they disturb the life cycle of insects by reducing their reproduction rate. Metamorphosis is hindered when actinomycetes feed on larvae-produced chitin before the larvae becoming pupae. Actinomycetes are gram-positive and aerobic, hence can be cultivated easily on simple growing media [33].
3.5 Brands of EM
The increasing global popularity of the use of EM as crop production broad-based organic materials is one of agriculture’s innovative solutions to farming. Various EM brands have been shown to improve crop quality and growth [34]. Various EM brands are discussed in detail in the succeeding sections.
3.5.1 Multiplied (M-) EM
Stock EM is multiplied to reduce cost. Multiplied-EM is a mixture of stock EM with molasses and water in a ratio of 1:5:94. After mixing the ingredients, the resultant solution is stored in an airtight container for between 10 and 14 days between 20 and 25°C until the pH is 3.7. During this time, the microbes enter a growth phase and multiply to reach a microbial population and composition like that of the stock EM. To maintain the quality of multiplied EM, they should be stored between 10 and 20°C [35, 36].
3.5.2 EM-fermented plant extracts (EM-F.P.E)
Ingredients used for EM-fermented plant extract production: chopped fresh weeds (20L—not compressed); chlorine-free water (16 L); molasses 480 ml (3%); multiplied-EM 480 ml (3%) [36]. Weeds or plants that possess repelling properties, for example, herbs, grass, syringa, clover, and khakibos are used to produce EM – EM-fermented plant extract. Plants are chopped fresh into 2–5 cm pieces and deposited into a sealable bucket during brewing. The multiplied-EM is then mixed with water and the resultant solution is poured into the bucket containing the chopped plant material, and the bucket is closed. After 2–5 days, the fermentation of the plant constituents begins, and a lot of carbon dioxide is generated and released through an air trap. The process goes on until the pH drops below 3.7 at which point the solution is filtered to remove the plant materials [3, 35, 36]. EM-F.P.E. acts as a disease suppressor and repellent, and it also contains vitamins, enzymes, hormones, and amino acids. The EM-F.P.E. is either sprayed on the crop with a sticker or applied to the soil through irrigation during the growing season [3, 35, 36].
3.5.3 EM 3-in-1
EM 3-in-1 is one of the strongest EM-based insect repellents. This is produced in a similar way as EM-F.P.E. except for the ingredients used. About 400 g each of chili pepper, ginger, and fresh garlic are chopped, and 200 g of black pepper is powdered, while 600 ml of Multiplied-EM and 18 L of water are used [35, 36].
3.5.4 EM-5
EM-5 is a mixture of EM1 (multiplied EM), water, vinegar, strong distillation alcohol (>30%), and molasses. Following ingredient mixing, the resultant is fermented in a tightly closed container for at least 30 days or until carbon dioxide production ceases. During the fermentation process, herbs such as red pepper and garlic are added. Thus, to strengthen the natural immune system against diseases and attacks by destructive pests, the resultant solution is applied to the targeted crop [35, 36].
3.5.5 EM-bokashi
EM-bokash is a mixture of multiplied-EM with quality and fresh organic materials such as wheat bran, fish meal, or rice bran. Following the mixing of the ingredients, the resulting mixture is kept for up to 2 weeks in tightly closed containers.
The final product is used for the following:
3.5.6 EM-fermented fish (EM-F.F)
To allow smooth plant growth over time and from one season to the next, EM-F.F is added to the soil, thus releasing nutrients such as phosphorus and nitrogen slowly over time. The fish are ground to fine powder during preparation to enable accessibility to microorganisms. Before spraying on the plants, the resultant mixture is combined with multiplied EM [3, 35, 36].
3.5.7 EM-fermented chicken manure
Because EM-fermented chicken manure provides phosphorus and nitrogen to plants, it plays a similar role to that of EM-fermented fish. The ingredients used include an equivalent of 1% bokash, extended EM, and chicken manure.
3.5.8 EM-fermented kitchen garbage
For EM-fermented kitchen garbage, organic waste that is generated in the kitchen is fermented using multiplied EM to produce a nutrient-rich fertilizer for plants. The production procedure for this is like that of EM-F.P.E. production [35, 36].
3.5.9 EM-X
This distinct version of EM liquid has been certified for human intake. This beverage EM (C [EM-X]) is an antioxidant cocktail that is derived from papaya, seaweed, and unpolished rice fermentation with grouped yeast, photosynthetic bacteria, and LAB EM. This is composed of EM and mixed plant extracts. EM-X is constituted of at least 40 minerals and antioxidants (including lycopene, ubiquinone, quercetin, kaempferol, pannexin, ascorbic acid, oryzanol, flavonoids and tocopherol) as well as some bioactive substances including amino acids (such as nicotinamide adenine dinucleotide, I-alanine, l-glutamine, and nicotinamide mononucleotide), peptides, and nucleotides [37]. The consumption of EM-X daily overtime leads to a reduction in free radicals in the body and can potentially lead to the reduction of cancers and boosting of the immune system [35, 36].
3.6 Application of EM
According to Olle and Williams [38], EM are effective for crop production and are environmentally safe. According to previous authors, EM are produced in over 40 countries of the world using local microbial isolates, environmentally friendly, and effective for crop production. Their applications are numerous and diverse, ranging from aquaculture, animal, and crop production as well as environmental management. Various brands of EM are thus applied under different conditions in many ways as discussed in the following sections.
3.6.1 Inoculation of EM into the soil
EM can either be sprayed on plants or be applied as a soil drench during crop production. A dilution ratio of 1:500 multiplied by - EM in water or EM-FKG (kitchen garbage) when applied on the soil is used. For EM-F.C.M or EM-F.F, a dilution ratio of 1:300 is recommended. An equivalent of 2.5 tons of bokash or less is applied to soil per hectare. Applications above 2.5 t ha−1 can be detrimental/toxic to the plants because of organic acids, which can potentially damage plant roots. EM-bokash is usually applied 10–14 days before planting and is placed between 10 and 15 cm away from roots [3, 35, 36]. EM in combination with other substances such as molasses has been shown to improve in onion, peas, and sweetcorn [39]. The study of zu Schweinsberg-Mickan and Müller [40] showed that the addition of EM to the soil significantly increased soil microbial activity. A global metadata analysis has previously shown that soil inoculation with EM results in about a 16% yield increase in all crops, but legumes show a superior response [41]. For example, EM inoculation in the soil significantly increased yield, seed quality traits, and leaf photosynthesis in the common bean [42]. In general, a host of studies have shown a significant increase in crop yield after the inoculation of the soil with EM [43, 44, 45].
3.6.2 Spraying EM on leaves
The spraying of effective microorganisms on plant leaves serves as a prophylactic spray mainly for insect and disease control. This is done earlier in the season and terminated when the crop has been harvested. A dilution ratio of 1:1000 of multiplied-EM, EM-F.P.E. or EM-5, or a mixture of different EM derivatives, is recommended, although a stronger dilution can also be used [3, 35, 36].
3.6.3 Soaking seeds in EM
Seeds are soaked in 0.1% EM water before planting. Smaller species are soaked for 30 minutes, while the bigger species are soaked for up to 6 hours. Seeds are then dried under the shade to reduce the chances of sticking together [3, 35, 36] and planted in the field.
3.6.4 EM irrigation (fertigation)
Irrigation water is often used to supply multiplied EM or EM derivatives to the soil. A dilution ratio ranging between 1:1000 and 5000 multiplied-EM or EM-F.P.E to water is used [3, 35, 36].
3.6.5 Insect control
Controlling and suppressing pests through the introduction of beneficial EM to the crop’s environment is one of the EM functions in biological control measures. Harmful insects can potentially be repelled by the odor emitted by EM as it serves as a prophylactic spray. EM-5 and EMF. P.E. are good prophylactics that repel insects and are not toxic to frogs, ladybirds, dragonflies, and spiders, among others. However, effective microorganisms do attract fruit flies and can sterilize the females [35, 36]. By increasing the antagonistic activities and competition of the microbes in EM inoculants, pathogens and pests are controlled and/or suppressed by these natural processes [3, 35, 36].
3.7 Benefits of applying EM
Some beneficial impacts of EM in agricultural production are as follows:
Enhancement of the chemical, biological, and physical environment of the soil (improve organic matter fertilizer efficacy) and suppression of pests as well as soil-borne pathogens
Enhancement of flowering, germination of seeds, ripening, and fruiting in plants
Increased yield in crops and improvement of crop photosynthetic capacity
Crop quality and yield are thus enhanced, resulting from the above-mentioned beneficial effects of EM [3].
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 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].
4. Organic manures
Traditional agricultural practices include applying organic manures at agronomic rates for plant nutrition delivery and advantageous impacts on physical qualities [55]. Due to a growing interest in the disposal of the enormous volumes of organic waste being generated over the past few decades, the impacts of organic manures on soil qualities have attracted new attention.
4.1 Effects of organic manures on physical and chemical properties of soil
According to Liu [56], organic manure has an impact on the soil’s bulk density, stability, aggregation, pH, buffer capacity, cation exchange capacity, soil encrustation, water infiltration, soil penetrability, moisture content, drainage, tilth, aeration, soil temperature, as well as the supply and availability of nutrients for plant growth.
4.1.1 Soil bulk density
The physical qualities of the soil are improved by the addition of organic manures because it increases the amount of organic matter in the soil and the activity of its microbial population [57]. As a result of net increases in soil organic C, there is a direct correlation between changes in bulk density and water-holding capacity in the soil [58]. Because the denser mineral portion of the soil is diluted by the addition of organic manures, the bulk density of the soil falls. Organic manures have larger and more numerous pores and are less thick [59]. The humic components of organic manures reduce the flexibility, cohesiveness, and stickiness of clayey soils, causing the development of stable aggregates in the soil [60]. After the lag phase that occurs after adding organic manures to soils, the amount of microbial biomass increases. The physical entanglement of fungal hyphae and the synthesis of extra-cellular polysaccharides, which connect soil aggregates and hence boost aggregate stability, occur in conjunction with an increase in the microbial biomass pool [55]. In comparison to fresh organic manures, composted organic manures cause a slower, more gradual rise in aggregate stability [57].
4.1.2 Soil pH and cation exchange capacity
Cations like calcium, potassium, and magnesium are held in exchangeable forms by humus colloids so that they can be used by plants and are not washed away by water. According to Ampong et al. [60], “Organic matter also provides much of the pH buffering capacity in soils through its cation exchange capacity and acid and base functional groups.” According to Fang et al. [59], applying organic manure caused the pH of the soil where composted organic materials had been mixed into acidic soil to rise. However, neutral or basic soils did not yield the same findings. Masmoudi et al. [61] demonstrated the high CEC of soils treated with organic manures. When compared to clay soil, the CEC on sandy soil rose by a ratio of 5–10.
4.1.3 Soil water content and soil water holding capacity
By increasing infiltration capacity and hydraulic activities, the addition of organic manures to the soil reduces surface crusting, reduces soil particle displacement by raindrops, reduces runoff water, reduces water lost through evaporation, improves drainage, and enhances root penetration [57]. By adding organic manures to soils, soils can hold more water, which is regulated by the number, size, and distribution of pores. At low tensions, an increase in the quantity of tiny pores is principally responsible for an increase in water-holding capacity. The amount of surface area and the thickness of the water films on these surfaces dictate the soil moisture content at higher pressures where practically all the pores are air-filled [58]. The addition of organic manures to soils also expands the soil’s specific surface area and boosts its ability to hold onto water under higher pressures [62].
4.1.4 Soil nutrients
Micronutrients, phosphorus, sulfur, nitrogen, and other elements are contained in organic manures and are gradually released through mineralization. The degree to which organic manures are mineralized is greatly influenced by their quality. As a result, N mineralization and immobilization, which, in turn, are regulated by C: N, lignin: N, polyphenol: N, and (lignin + polyphenol): N ratios, lignin and polyphenols, N% of the organic manure used, and moderate N release from organic materials [63]. In the early stages of decomposition, mineralization or immobilization processes will predominate depending on the chemical makeup of the organic manures, particularly the C: N ratio. The rate of material decomposition and subsequent soil turnover of decomposed C and N determine how much inorganic N is released from organic manures into the soil [63]. According to Ndambi et al. [64], the amount, kind, and duration of manure utilized all affect how successful it is as a source of nutrients for plants. Long-term addition of low-quality organic inputs can boost soil organic C build-up without necessarily boosting output. For instance, cropping system research in India found that using wheat straw and urea together significantly lowered yields, but using Sesbania green manure and urea together increased yields when compared to using urea alone [65]. According to Adekiya et al. [57], low-quality organic manures have low concentrations of soluble C and N, which are necessary to boost the activities of the soil’s microbial pool and, thus, reduce crop output. Numerous crop wastes and animal manures can temporarily immobilize nitrogen (N) and have low-quality nitrogen contents that vary from 1.8 to 2.0%. Several crops have been produced using fresh organic manures as well as composted organic manures as a source of nutrients, with varied degrees of success. The results of adding organic manure to a soil depend on the quality of the manure and the characteristics of the soil. Manure application rates of 5.5 to 11 t ha−1 for field crops and double that amount for plants needing more nutrients have been recommended for South Africa [66]. The precise amount of organic manure required for optimal crop production is difficult to predict since it depends on the type of manure used, the type of soil, the needs of the crop, and the current environmental circumstances. Small-holder farmers in South Africa’s Eastern Cape Province apply manure at rates that range from 0.3 to 18.2 t ha−1 [67]. However, manure is applied at rates of 25–100 t ha−1 [68]. Manure may be harmful in high concentrations to humans, animals, and plants [69]; hence, care must be taken to limit any negative consequences. According to Reimer et al. [70], 100 t ha−1 of compost added annually is sufficient to alter the physical properties of the soil and boost output. Numerous studies have shown that applying both organic manures and inorganic mineral sources together has a greater positive impact on growth and production than applying either one alone. This can be because organic manures do not have enough of all the necessary plant nutrients. When inorganic fertilizers are mixed with organic manures, their soluble minerals will mix with the organic portion because inorganic fertilizers are quickly leached. The nutrients will then be gradually released over time in the form of microbial pool by-products and under the influence of organic acids [57].
4.2 Types of organic manures
You can use organic manures on soil as compost or right out of the bag. Fresh organic materials have higher net N mineralization rates and higher inorganic N concentrations than composted manure, according to Cambardella et al. [71]. According to Paul and Beauchamp’s study from 1994, plants treated with fresh organic manure showed more dry matter in their first growth season than plants treated with composted manure.
4.2.1 Compost
As organic materials are broken down, decomposed, and stabilized by natural microorganisms in a moist, warm, aerobic environment, carbon dioxide, water, minerals, and stabilized organic matter are produced, and pathogenic microbes are eliminated by enzymatic combustion and the heat generated [72]. Organic waste can be recycled by composting and used as a soil amendment. Composting organic waste has been shown to improve soil fertility, soil structure, and plant growth. According to Cambardella et al. [71], applying un-composted trash or compost that has not been stabilized to soil might cause phytotoxicity and nutrient immobilization.
4.2.2 Animal manures
Animal manure is used in Africa to improve soil fertility, and its advantages are well known. Animal food modifications, collection methods, and storage methods all affect the nutrient content of animal dung. Before the development of mineral fertilizers, manure and other livestock waste products were the only methods of increasing soil productivity. Animal manure application is a frequent practice in Zimbabwe, and it has been discovered that the quality of manure as a source of plant nutrients varies greatly in terms of chemical composition [73]. The most frequent manures used in southern Africa are those produced by goats, sheep, cattle, and chicken, with cattle producing two-thirds of the total amount of manure utilized and sheep and goats producing the remaining third. Species, animal diet, mineral particle content, and storage conditions all have a significant impact on the nutritional makeup of animal manures [66]. However, in the Eastern Cape Province, the nutrients in animal manures fall within the ranges recorded for manures in West African nations and range from 9.9 to 16.7 g N, 2.0 to 3.6 g P, and 17.2 to23.7 g K kg−1 [68]. The manures have a low P content, though. The differences in animal diet that affect how nitrogen is divided between feces and urine cause the nutrient content of manures to vary. When animals are fed high-quality food, N is lost by volatilization and expelled through urine [74]. The amount of nitrogen (N) excreted in feces is thought to rise when diets with a significant number of tannins are consumed. N in manures from animals given a diet high in tannin is particularly resistant to mineralization in the soil, according to a study by Halvorson et al. [75]. According to Mkile’s [68] analysis of the nutritional content of various manures in the Eastern Cape region of South Africa, goat manure had the highest levels of N, P, and K, whereas sheep dung had the lowest levels.
5. Conclusion
Through the rapid proliferating of their constituents, more advantageous microorganisms, and subsequent suppression of soil-borne harmful organisms, the application of various brands of EM has been demonstrated to boost crop growth and quality, lowering the occurrence of pests and diseases. They may also effectively mineralize organic soil matter, which enhances nutrient availability and is how EM might boost soil health and crop growth. It has been well documented that EM has positive benefits on agricultural output by promoting plant germination, blooming, fruiting, and ripening. However, several studies have not consistently demonstrated the positive effects of EM on yield, indicating that the findings are not repeatable.
Additional information
“Parts of this chapter were previously published in the masters dissertation by the same author: Lindani Ncube. Evaluation of the effective micro-organisms (EM) on soil chemical properties and yield of selected vegetables in the Eastern Cape, South Africa. 2008. [Unpublished MSc Dissertation. University of Fort Hare. Available from: http://vital.seals.ac.za:8080/vital/access/manager/Repository/vital:11886?site_name=GlobalView&view=null&f0=sm_subject%3A%22Microorganisms+--+South+Africa+--+Eastern+Cape%22&sort=null”
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