Influence of Organic Fertilizers on Productivity of Barley: A Review

Barley (Hordeum vulgarae L.) is cultivated in every region of Ethiopia implicating its wide ecological plasticity and physiological amplitude (Berhane et al., 1996). It is one of the most useful cereal crops in the world, ranking fourth after wheat, maize and rice in terms of production (Lapitan et al., 2009). In Ethiopia, barley based on area of production and based on yield per unit area rank fifth and third respectively, among all cereal crops (CSA, 2014). The production of barley in Ethiopia has not satisfied the demand of farmers due to many factors from thus are biotic including rodents, pathogens, diseases, weed, pests, insects and abiotic stress like drought, flooding, temperature stress, salinity, poor management practice, frost, poor soil fertility, agronomic practice but, the most important factors that reduce yield of barley in Ethiopia are the use of inappropriate organic fertilizer (Assefa, 2017). The various factors accounting for the poor soil fertility include topography, soil erosion, deforestation, population pressure and continuous cultivation without proper soil fertility maintenance.
       
Organic fertilizer plays a great role in soil fertility and crop production, but local farmers does not give more focus on the application of organic fertilizer in soil fertility and crop production even they are around them (Negassa et al., 2003; Woldeyesus and Chilot, 2002). Low productivity of barley is mainly due to traditional methods of production and poor soil fertility. Since the main barley producing areas of the country are mostly located in the highlands, serious soil erosion and absence of proper soil conservation practices in the past have resulted in soils with low fertility and pH (Grando and Helena, 2005). Particularly scarcity of organic fertilizer is the main factor that severely reduces the yield of barely. Barley yields are increased by applying different organic fertilizers on some soil (Bulman and Smith, 2003).  In addition, organic fertilizer is commonly the most limiting nutrient for crop production in the major world’s agricultural areas and therefore adoption of good organic fertilizer strategies often results in large economic benefits to farmers. Organic residues such as crop residue are important for smallholder farmers because it is cheap and easily available sources of nutrients and environmentally friendly as compared to inorganic fertilizer (Almaz et al., 2017). Similarly, Munck (2002) reported that organic fertilizers such as poultry manure, farmyard manure and compost can therefore be used to reduce the number of toxic compounds (such as nitrate) produced by conventional fertilizers.
       
As Dejene and Lemlem (2012) reports by applying organic fertilizer can improve crop growth because supply plant nutrients including micronutrients as well as improving physical, chemical and biological properties of the soil, it is important for improving the soil structure that making a better environment for root development. According to Khasawneh and Othman (2020) reports soil quality is improved through increased soil organic carbon, cation exchange capacity, soil water content as well as beneficial soil microorganism due to addition of organic matter to soil. Applying of organic fertilizers are important to preserve the balance in nature, to improve soil fertility, help disease and pest control, withstand the biodiversity and get high quality products (Arzu, 2020). Hence, the objective of this paper is to review the influence of organic fertilizers on productivity of barely.
 
Literature review
 
Ecological requirement of barely
 
Ethiopia has enormous potential for barley production. Barley can be cultivated at altitudes between 1500 and 3500m but, is predominantly grown between altitudes of 2000 to 3000 m (Berhane et al., 1996). As Birhanu et al., (2005) reported food barley is commonly cultivated under extreme marginal conditions of drought, frost and poor soil fertility better than other cereal crops in the highland of Ethiopia. Its adaptability ranges from 1,400 to over 4,000 meters above sea level under highly variable climatic and edaphic conditions (Asfaw, 2000). Barley performs well on soil with medium texture, permeable, pH 6.5 to 7.5 and fertile and require 600-1000 mm with uniform rain fall distribution during the crop growing season. 
 
Soil fertility status of Ethiopia
 
The relationship between chemical, biological, physical and anthropogenic processes is determining the soil direction (accumulation or depletion) because of the dynamic nature of soil fertility. Tropical soils, including those of East Africa, are commonly described as being acid, infertile and often incapable of sustained agricultural production. This is not universally true because of the diversity in terms of the environmental and soil-forming factors and there is proof of some successful sustained soil management systems in many ecosystems of the tropics (Kemelew et al., 2011). However, a considerable proportion of the soils are highly weathered, have low nutrient reserves and therefore limited capacity to supply phosphorus, potassium, calcium, magnesium and sulphur. Some have adequately strong soil acidity for soluble aluminum to be toxic for most crop species. In order producers to understand satisfactory yields and profits to their limited resources under these soil conditions, they need to use better soil fertility management that they always find unreasonable. Hence, even though soil fertility in most areas of east Africa is low, farmers have not been able to redress the downward spiral of soil fertility.
       
In Ethiopia, particularly at Tigray region the major constraint to barely production is low soil fertility. Poor soil fertility is attributed to the many years of continuous cultivation with poor nutrient recycling, deforestation, soil erosion improper land use systems etc. Moreover, most of the crop residues are collected for livestock feed and much of the animal manure is used for fuel, neglecting nutrient recycling. As possible consequences of the aforementioned land degradation processes, reported very low content of N, P and K in most of the soils sampled in Tigray region. Di-ammonium Phosphate (DAP: P₂O₅ 46% and N 18%) and urea [CO(NH₂): N 46%] are the two main source of mineral fertilizer that have been recommended for use in cereal production in Ethiopia. However, only 30 percent of the total barley fields were applied with mineral fertilizers in Ethiopia in general (Kotler and Armstrong, 2003). Moreover, most farmers apply an under dose of the recommended fertilizer rates due to financial limitations, fear of drought, or limited awareness on the importance of right dose application.
       
The application of fertilizer also needs site specific prescription since soils in the Tigray region are highly heterogeneous in nutrient status, pH, nutrient holding capacity and other chemical properties (Kemelew and Alemayehu, 2011). This is demonstrated by study, which reported up to 124% barley yield increment in fields applied with addition of 64 kg N and 21 kg N P₂O₅ per ha in Dejen (northern Ethiopia), while in another site (Maiquiha) the yield increment was relatively low (40%). In addition to macro nutrients, micro nutrients have become deficient in some parts of the country. According to soil fertility status graphics of Ethiopia, available sulfur and extractable iron, zinc and boron are deficient. These deficiencies result in reduced productivity and poor grain quality. Zn and Fe are reported to be the most common micronutrient deficiencies in human population affecting health of over three billion people worldwide (Kemelew and Alemayehu, 2011). Zinc deficiency causes impairments in brain development, wound healing and increases susceptibility to infectious diseases including diharea, pneumonia and malaria by weakening the immune system. Iron deficiency impairs physical growth, mental development and learning capacity in children, reduces productivity in adults and represents the most common cause of pneumonia. In most cases, the reason behind Zn and Fe deficiencies is inadequate nutritional intake of Zn and Fe (Kemelew and Alemayehu, 2011).
 
Barely production constraint in Ethiopia
 
There are many factors that affect the production and productivity of barley among those one is using poor yield-potential of varieties at the farmer levels. The statistics on farmers using modern seed for growing barley is less than 1 per cent (0.6 per cent) of barley growers uses modern seed varieties far less than the other cereals except sorghum (CSA, 2017/18). The shortage of improved barley varieties is associated with both the research system, which is required to generate primary or early generation seeds and the seed enterprises that produce and distribute seeds. Woldeyesus and Chilot (2001) reported that lack of improved varieties, poor adaptability of the improved varieties of the crop, disease and pests are some of the bottleneck problems and the lower yield in barley production and productivity in Autumn (Belg) season.
       
The other cause for low productivity of barely is due to the poor soil fertility of farmlands. Core constraints of Ethiopian soils include depletion of soil organic matter (SOM) due to widespread use of biomass as fuel, depletion of macro and micronutrients, removal of top soil by erosion, change of soil physical properties and increased soil salinity with time (IFPRI, 2010). On top of these, the usage of fertilizers in the country is not based on soil test results and below the recommended level; farmers do not fully implement the recommended soil management practices. These have resulted in a steady decline of nutrient levels in the soil (Diriba et al., 2013). Depletion of soil fertility leads to declining crop yields and a rise in the number of foods insecure people (Chillot and Hassan, 2010). As a result, application of fertilizers containing N and P [Urea and Diammonium Phosphate (DAP)] began in the late 1960s, producing dramatic increases in the yields of several crops (Wassie and Tekalign, 2013). On the other hand, Wondwosen and Sheleme (2011) reported little or no attention has been given to other macro and micronutrients, thus leading to unbalanced fertilization and poor nutrient management and crop quality. It is apparent that, until recently, the use of commercial fertilizers in Ethiopia has not been in harmony with the economy of the farmers mainly since farmers were not using the fertilizer based on soil and crop requirements, while at the same time, the yield return from the applied fertilizers was low. This is because blanket application of DAP and Urea was not based on crop need, soil nutrient dynamics and agro ecological factors (Abreha and Yesuf, 2008), which leads to either nutrient toxicity or deficiency (Ray et al., 2000).
       
Farmers are using only NP fertilizer, other essential nutrients such as S and B are getting less consideration/ ignored due to less consideration by previous researchers on responses of food varieties in terms of grain yield and quality. Recent studies have indicated that elements like N, P, S, B, Fe, Zn etc. are becoming depleted and deficiency symptoms are being observed on major crops in different areas of the country (ATA, 2016).  According to soil inventory data, most of nutrients such as nitrogen (N), phosphorus (P), sulfur (S), boron (B) and zinc (Zn) are deficient in 86, 99, 92, 65 and 53% of Ethiopian soils (Ethio-SIS, 2016). Although micronutrient concentrations increase with decreasing soil pH, studies have found that B deficiency is particularly widespread in acidic soils of the southern highlands which limiting cereal yields (Elias, 2019).
 
Response of barely to various organic fertilizers
 
Poultry manure
 
According to Grando (2005) indicated that all the essential nutrients required for crop production available in poultry manure fertilizer and its value has been recognized for centuries as an organic fertilizer and a source of plant nutrients. It will help poultry producers develop an easy nutrient management plan that meets permitting authority standards (FAO, 2014). Likewise, Almaz et al., (2017) reported that integrated application of 50% NPK + 50% poultry manure increased nutrient (N, P and K) uptake of maize over sole poultry manure and sole inorganic fertilizer. Even with its beneficial effects on plant growth, however, manure constitutes only small percentage of the nutrients applied to crop land when compared to commercial fertilizer. Poultry manure fertilizer is not used to its maximum potential for several reasons, including: lack of information on its value as a source of plant nutrients, failure to recognize how and where to use it and lack of recognition of its economic value (Grando, 2005).
 
Animal manure
 
Animal manure is often prepared from a blend of animal feces and bedding straw. Manure is organic matter that’s used as organic in agriculture. Compost and green manure are the sources of manure but animal feces are the most. Manures contribute to the fertility of soil by adding organic matter and nutrients such as nitrogen, that are utilized by bacteria, fungi and other organisms in the soil (FAO, 2014). According to Arzu (2020) showed that increased the grain yield, plant height and 1000 grain weight of barely crop as a result of applied cattle manure + liquid fertilizer treatment. Animal manure had been used as a source of local fertilizer in the many developing countries across the globe for many centuries. Proper use of manure and compost is important for both a production and environmental standpoint. Applying rates that are too low can cause to nutrient deficiency and low yields. On the opposite hand, too high a rate can cause to nitrate leaching, phosphorus runoff, accelerated eutrophication of lakes and excessive vegetative growth of some crops. Thus, understanding the way to manage manure is vital for any farming operation with livestock that relies on manure as a main source of nutrients, as also for vegetable producers who have access to a cheap supply of manure, compost, or other organic nutrient sources.
       
Nutrients contained in manures are released more slowly and are stored for an extended time within the soil ensuring longer residual effects, improved root development and better crop yields.  Manures are usually applied at higher rates, relative to inorganic fertilizers (FAO, 2014). Inorganic fertilizers when applied at higher rates, they provide residual effects on the expansion and yield of succeeding crops. Improvements of environmental conditions as well as the need to reduce cost of fertilizing crops are reasons for advocating use of organic materials, organic manures improve soil fertility by activating soil microbial biomass (FAO, 2014). Application of manures sustains cropping system through better nutrient recycling; manures provide a source of all necessary macro- and micronutrients in available forms, thereby improving the physical and biological properties of the soil (FAO, 2014).
 
Vermicompost
 
The term vermicomposting means the utilization of earthworms for composting organic residues. Earthworms can consume practically all types of organic matter and they can eat their own body weight per day as an example one kg of residues can be consumed by one kg of worms every day. The excreta (castings) of the worms are rich in nitrate, available forms of P, K, Ca and Mg (Ejigu, 2012). The passage of soil through earthworms promotes the expansion of bacteria and actinomycetes. Actinomycetes thrive within the presence of worms and their content in worm casts is quite sixfold that within the original soil.
       
More than 50, 000 number of worms can be produced in a moist compost heap of 2.4 m by 1.2 m and 0.6 m (Ejigu, 2012). The aeration, decomposition and mix of the material of compost heap are speed up due to the release of worms into a compost heap.Turning the heaps is not necessary where earthworms are present to try to the blending and aeration. The ideal environment for the worms may be a shallow pit and therefore the right kind of worm is important. As Ejigu (2012) showed that Lumbricus rubellus (red worm) and Eisenia foetida are thermo-tolerant and then predominantly useful. Field worms (Allolobophora caliginosa) and night crawlers (Lumbricus terrestris) outbreak organic matter from below but the latter do not thrive during active composting because it is highly affected by high temperature and may be died more simply than the others. European night crawlers (Dendrabaena veneta or Eisenia hortensis) are produced commercially and have been used fruitfully in most climates. These night crawlers grow to about 10-20 cm. The African night crawler (Eudrilus eugeniae), may be a large, tropical worm species. It tolerates higher temperatures than Eisenia foetida does, provided there is sufficient humidity. However, it cannot survive at temperatures below 7°C and has a narrow temperature tolerance range.
       
Vermicomposting is in use in many countries (CSA, 2014). According to Satyanarayana et al., (2002) indicated that vermicompost and farm yard manure improve soil physical properties such as bulk density, water holding capacity, porosity and chemical properties such as organic carbon, cation exchange capacity, total N, available P, etc. In addition, vermicompost and farm yard manure acts as a mixed complete fertilizer because they supply all major nutrients (N, P, K, Ca, Mg and S) that are necessary for plant growth as well as the micronutrients (Fe, Mn, Cu and Zn) (Dejene and Lemlem, 2012). vermicompost has vitamins, enzymes, humic substances and microbial activity that can be used as an effective fertilizer and soil amendment material (Gupta et al., 2020). According to Ceritoglu et al., (2021) report 20% concentration of vermicompost stimulated root and shoot growth and led to the improved growth in chickpea whereas 10% was sufficient to observe a significant effect on other species.
 
Farm yard manure
 
Farm yard manure is a varying mixture of animal manure, urine, bedding material, fodder residues and other components is the most common form of organic manure. Farmyard manure has a high proportion of organic material, which nurtures soil organisms and is essential in maintaining an active soil life (CSA, 2005). Jarvan et al., (2017) reported that one of the more valuable organic fertilizers is farm yard manure which maintaining soil fertility in the systems of alternative agriculture. Farmyard manures are the major source of nutrient supply on small farm holdings (Fageria, 2012). Only about half of the nutrient content of farm yard manure becomes available for growth during the first year after it has been applied to the soil, the rest is conducted through soil biotic methods and the nutrients are released in the following years. The high organic matter content and the active soil life improve or maintain friable soil structures, increase the cation exchange capacity, water holding capacity and infiltration rate and reducing the risk of soil pests building up (CSA, 2014). Indigenous methods of preparing and using farm yard manure vary widely depending on the ecological zone, access to bedding material from crop or forest land, access to crop residues and fodder, labour availability and other factors.
       
Application of farmyard manure in the soil generally increases CO₂ emissions. Farmyard manure application to the soil can usually be carried out with two techniques: surface and subsurface applications. In subsurface application, farmyard manure is commonly spread on the soil and then stirred with tillage machinery such as a plow and rotary tiller. Liquid manure can also be inserted into the soil. Some researchers have reported that injection of liquid manure can reduce the nutrient transport by run-off and reduce NH₃ emissions compared to surface application (CSA, 2005). An increase in wheel traffic will result in a decrease in CO₂ emissions from the soil to the atmosphere and a similar effect will be seen in the manure is a varying mixture of animal manure, urine, bedding material and fodder residues (Bayehe and Stefania, 2011).
 
Role of organic fertilizer on barely production
 
Compost is considered as an important source of humus; macro- and micro elements carrier and in the same time, increase the activity of the useful microorganisms. Use of composts is important to against disease by developing of resistance in plants and stimulation of the competing microorganisms (Ebrahimi et al., 2018). Application of organic fertilizers (FYM) with inorganic fertilizers is a better approach to increase barley yield than application of either organic or inorganic fertilizers (Bayehe and Stefania, 2011). Ghosh et al., (2012) also reported that combined use of organic manure and NPK fertilizers was significantly increased in NPK uptake of wheat. Lingaraju et al., (2010) reported that using 7.5 t/ha farm yard manure and 100% recommend fertilizer resulted in significantly higher gross return and net return which were similar with vermicompost at 2.5 t/ha and 100% recommend fertilizer regarding gross returns. The residual effect of organic fertilizers on yield, including cattle manure, has been found to be positive in barely. Therefore, there was a direct effect of cattle manure on green ear yield and grain yield; the tiller number per plant were influenced by the application kinds of manure used and significantly increased barley yield was observed in kinds of application as compared with the control (Bayehe and Stefania, 2011). The availability of nutrients by incorporating nutrients through the mineralization-immobilization process as a source of energy for microbial activities or as precursors to soil organic matter and lessening P fixation in the soil is affected by organic manures (Sharma et al., 2008).
       
The barley exhibited significantly response about the number of tillers per plant, application of mixed manure as compared with other treatments, also the results showed increase in the percentage of standard tiller in all treatment fertilizing various treatments (Bayehe and Stefania, 2011). The application of mixed manure has indicated maximum increase in percentage of standard tiller at 80.84% then it is followed by the chicken manure treatment at 76.65% then the common fertilization at 72.83%, the sheep manure at 69.8 % and no manure at 61.45% (Akar, 2004). These results indicate that poultry manure or chicken manure mixed with fertilizer sheep provides the plant greatly benefit from the nutrients leading to increased production and quality (increase the size of tillers) (Akar, 2004). According to Dejene and Lemlem (2012) reported that organic fertilizer application improves crop growth by adding plant nutrients including micronutrients as well as enhancing physical, chemical and biological properties of the soil, thereby refining the soil structure by providing a better environment for root development.

Organic fertilizer application such as animal manure, poultry manure, farm yard manure and vermi compost is important to increase the yield and yield component of barley. Because using organic fertilizer had beneficial residual effects on crop production that can bring better improvement in the productivity of the crop. This is might be due to the stimulation effect of organic manures on improving the physical properties of the soil, increasing soil fertility and increasing the availability of many nutrient elements to plant uptake, which in turn on improving the growth of barley plants and consequently positively affected yield and yield components. It concludes that using organic fertilizer is advisable since it can be prepared from locally available materials that are cheap and easily found in the surrounding and it is essential to enhance soil fertility and to safe the environment from toxic and pollutant.

In Ethiopia, around 85% of peoples living in rural area and engaging in agriculture. However, due to low soil fertility the productivity of crops are limited and decreased year after year. On the other hand, use of mineral fertilizers alone has caused adverse effect on soil nutrient balances and, thus reduced crops growth performance and yield. To alleviate this problem using organic fertilizer is preferable to improve yield and to safe the environment. Therefore, scaling up of organic fertilizer application practices on farmers field and further research in the amount applied per unit of land that have diverse soil properties is very important.

I declare no conflict of interest.

No one fund for this review paper.