CHAPTER ONE
INTRODUCTION
Background of The Study
Soil fertility is one of the important and essential components of a sustainable agricultural system in the Tropical climates. The fertility status of the soil is a subject of soil characteristics especially physical and chemical property of the soil ( Shehu et al, 2019)
Despite the indispensability of fertile soils, it has still been reported that land misuse and soil mismanagement, resulting from a desperate attempt by farmers to increase production of food, fibre, fuel wood and feeds for the growing population, has given rise to decline in land per capita, exercabated soil degradation with severe impacts on soil fertility and productivity (Ali et al, 2021). Decline in soil fertility, especially in cultivated soils; lead to decline in crop yields and it is wide evident. Amana et al. (2019) have shown that reduction of crop yields are a major concern in those regions where the attainment of food security is closely related with soil degradation due to nutrient mining. This has posed a great threat to the ability of the nation to support growing rural and urban populations (Ezeaku et al., 2018).
It has further been noted that the problem of soil fertility in South Eastern Nigeria is driven by a wide range of factors such as biophysical, chemical and socio-economic factors( Shehu et al, 2019) . This therefore creates a need for increase in soil productivity and its sustainability. Achieving this can be possible through making soil restoration and fertility management a. This has led to the development of various new approaches to maintain and protect the soils’ fertility resources. One of such approach is the use of biochar and cow dung to improve soil quality and productivity and consequently crop yield of food with important economic impact such as Amaranthus spp. (Gani et al, 2022)
Grain amaranth is a popular leafy vegetable cultivated in all ecological zones of Nigeria and in other West African countries (Sokoto and Johnbosco, 2021). The vegetable has a fast growth rate and is planted all year round, with irrigation in areas with minimal rainfall. There is high demand for this crop especially in urban areas where there is no primary cultivation of the crop (Schippers, 2018). This has resulted in making the vegetable an important commodity in our market and an important economic activity for rural women (Law-Ogbomo and Ajayi, 2019). Thus economic importance of Amaranthus therefore calls for proactive approach towards sustaining its production and one of such is the use of co-composted cowdung and mixed biochar.
Cattle manure has been used as a soil amendment in agricultural systems for centuries. The addition of cattle manure to soil provides several benefits by improving soil structure, fertility and increasing soil organic matter (McAndrewset al., 2020). However, it has been reported by Onwuka et al, (2019), that cow dung in its original form does not add much nutrients to the soil and also takes time to release its nutrients unless they are transformed.
One of the ways to transform cowdung or enhanced it is by the addition of biochar. Biochar has been shown to be very beneficial in higly weathered tropical soils, soils with low pH, or soils with low cation exchange capacity (Lehmann, and Rondon, 2020). Biochar increases the availability of C, N, Ca, Mg, K, and P to plants especially leguminous plants (Kauffman et al., 2020) because of the increase of the pH near neutral and its ability to absorbs and slowly releases fertilizers. (DeLuca et al.,2020).
Biochar is a solid material obtained from the carbonization of biomass. It is a carbon-rich product obtained by the slow thermochemical pyrolysis of biomass materials (Shih-Hao and Chieng-Sheng, 2021). Also Biochar can be defined as a solid material produced during a process known as pyrolysis from the thermo conversion of biomass under little or no oxygen for use in soils as an amendment, sequester carbon and off set carbon emission (Bell and Worrall, 2018). The production of biochar through pyrolysis helps at reducing agricultural and other forms of organic wastes. These wastes not only occupy large land spaces but also constitute environmental nuisance. When they are converted into biochar, they are changed into a recalcitrant form, rendering the carbon in biochar more resistant to biodegradation (Lehmann et al., 2019).
When biochar is applied to the soil, it increases the soil chemical properties (Onwuka and Nwangwu, 2020). This is observed in the amount of nitrogen retention in the soil, increased organic carbon content, pH, cation exchange capacity, decreased exchangeable acidity, S, and Zn (Novak et al., 2019). When biochar is applied to the soil it improves soil fertility and at such add to soil essential nutrient for plant growth, increased microbiological activity, mycorrhizal associations and create a microhabitat in soil (Steiner et al., 2018 and Warnock et al., 2021).Other important property of biochar is that when added to the soil, it helps to reduce the emission from biomass that would otherwise naturally degrade in the soils and liberate greenhouse gas (Winsely, 2021).
It has been shown to effectively maintain soil organic matter (SOM ) levels, increase fertilizer-use efficiency and increase crop production, particularly for long-term cultivated soils in subtropical and tropical regions (Chan et al., 2021, 2018; Deenik et al., 2018; Van Zwieten et al., 2018) and aggregate stability (Kimetu and Lehmann, 2018; Tejada and Gonzalez, 2021; Trompowsky et al., 2020). Furthermore, the application of biochar to soils might be a practical method to aid in the long-term maintenance of the soil organic carbon (SOC ) contents and soil fertility. Biochar is attracting interest both as a carbon sink and, possibly, a source of soil amendment (Jonathan, 2018).
Many researchers has worked on cow dung biochar or mixture of biochar and cow dung but not much works has been recorded in Southeast Nigeria on co-compositing cow dung and biochar to produce Amaranthus spp in has not been fully exploited.
The main objective of the study therefore was to determine the effect of Co-composted biochar and mixed biochar on soil chemical properties and growth of Amaranthus
Specific objective of the Study :
The specifically this project was aimed at :
Evaluate the effects of biochar added to cow dung during composting and biochar mixed with cow dung after composting ( co-composting) on soil chemical properties
Determine the effects of the treatments on growth of amaranthus
CHAPTER TWO
LITERATURE REVIEW
2.1 Soil
Soil can be defined as horizons near the earth’s surface which have been altered by the interactions over time, between climate, relief, parent materials, and living organisms.” (Soil Survey Staff, 2018).
2.2 Importance of Soil here
Soil is our life support system. Soils provide anchorage for roots, hold water and nutrients. Soils are home to myriad micro-organisms that fix nitrogen and decompose organic matter, and armies of microscopic animals as well as earthworms and termites. We build on soil as well as with it and in it(Soltner, 2020).
Soil plays a vital role in the Earth’s ecosystem. Without soil human life would be very difficult. Soil provides plants with foothold for their roots and holds the necessary nutrients for plants to grow; it filters the rainwater and regulates the discharge of excess rainwater, preventing flooding; it is capable of storing large amounts of organic carbon; it buffers against pollutants, thus protecting groundwater quality; it provides Man with some essential construction and manufacturing materials, we build our houses with bricks made from clay, we drink coffee from a cup that is essentially backed soil (clay); it also presents a record of past environmental conditions(Bockhaven et al., 2021).
Soil functions are general capabilities of soils that are important for various agricultural, environmental, nature protection, landscape architecture and urban applications. Four key soil functions are:
- Soil for food production.
Fertile soils are the foundation for agriculture because it provides a hospitable place for plants to live and grow by providing dissolved minerals, and moderating temperature fluctuations optimal for plant growth. There are around ten thousand species of plants that are consumed as food globally, all of which depend upon soil for their sustenance. Soil teems with microscopic and larger organisms that convert dead and decaying matter to essential nutrients like nitrogen, phosphorous, and potassium; improving soil structure, which ultimately leads to improved food and other biomass production(Laird et al., 2018). - Soil as a habitat for living biology and microbiology.
Soil is a habitat for biological beings and a reserve for genetic diversity for a large variety of organisms. None of the processes can truly be carried out without soil; hence, microbial to larger animals depend upon soil for their survival and protection. Some thrive on top of the soil, while others are found below the surface; around one-fourth of everything alive on the earth including fungi, bacteria, insects, and burrowing mammals uses soil as their habitat, all interacting to produce a complex ecosystem(Soltner, 2020). - Soil supports the root system.
Soil provides a medium for plant growth as porous structures in the soil can allow the passage of water and air. The root system of plants extends outward and downward through soil and as deeper and wider the roots goes; this anchorage allows plant roots to have access to water and nutrients. The compacted soils prevent the roots to explore due to excessive requirements in penetrative force as they must exert large physical energy to move soil particles aside. Therefore, a buildup of organic matter promoting the absence of compaction is necessary for favorable root growth(Bockhaven et al., 2021). - Soil acts as an important Carbon stock.
The soil is the largest terrestrial carbon pool and an elusive tool for climate change mitigation. Through photosynthesis, plants assimilate carbon and return some of it to the atmosphere, while the remaining carbon is consumed by animals or added to soil as litter when they die. This way a large amount of carbon is stored in the soil in the form of soil organic carbon. It is estimated that soil can sequester about 75% of the carbon pool on land which is three times more than carbon stored in living biomass. Therefore more research addressing the impacts of land management on soil carbon sequestration and ways to increase the storage time of carbon in the soil needs to be conducted to maintain a balanced global carbon cycle(Glaser et al., 2018).
2.2 Biochar
The term biochar was first used to refer to the pyrolysis residue of solid biomass produced for sequestrating carbon from the atmosphere in the soil (Lehmann, 2019). This carbon (C)-rich biochar substance is made by heating organic matter under a low-oxygen condition. Intensive biochar application in agriculture dates back to the early 1600s in Japan and possibly earlier in China (Ogawa and Okimori, 2021). When it is applied to soils, it does not only sequester carbon from the atmosphere into the soil but also perform additional functions such as improve soil fertility and enhance soil physical and chemical properties.
Studies have shown that adding biochar to the soil decreases soil bulk density, increases cation exchange capacity and enhances nutrient and soil water availability (Laird et al., 2018). It also improves plant nutrient uptake, water use and plant productivity which leads to reduction in the use of fertilizers (Glaser et al., 2018). These findings have sparked great interest in biochar research especially in the area of its impact on agricultural soils. Ndor et al (2020) added that Biochar incorporation into the soil as soil amendment improved both the physical and chemical properties of soil for crop production.
Biochar as carbon aromatic material is very recalcitrant and is itself a soil organic matter (Glaser et al., 2012) though different from other organic carbon pool due to its slow decomposition in soil. The physicochemical nature of biochar allows it to contribute to soil stabilization by aggregation, and water and nutrient retention. However, depending on the characteristics of the initial feedstock, the mineral ash content or mineralization of biochar may supply some important macro- and micronutrients that are beneficial for the plant and soil microbial community (Bruun, 2018). Biochar obtained from crop residues such as corn cob have high mineral ash content rich in important macro and micro nutrients such as phosphorus (P), potassium (K), silicon (Si), iron (Fe), sulphur (S), magnesium (Mg), and calcium (Ca). These nutrients are readily utilized by plants for improved growth. For example, Si uptake in plants has been linked to disease and pest resistance in plants (Bockhaven et al., 2021).
2.3 Cow Dung
Cow dung is the waste product of bovine animal species. These species include domestic cattle ("cows"), bison ("buffalo"), yak, and water buffalo. Cow dung is the undigested residue of plant matter which has passed through the animal's gut. The resultant faecal matter is rich in minerals. Color ranges from greenish to blackish, often darkening soon after exposure to air (Bockhaven et al., 2021).
Animal manures are valuable sources of nutrients and the yield-increasing effect of manure is well established. The organic manure improves soil fertility by influencing its physical, chemical and biological properties. It improves water circulation and soil aeration, and increases the soil moisture holding capacity (Soltner, 2020). According to Nyle and Brady (2021), the organic manure also improves the soil by the formation of clay humic complexes which increase the soil adsorbent capacity of basic nutrients (calcium, magnesium and potassium) and enhances the activity of microorganisms involved in the mineralization process.
2.3.1; Different forms of Cow dungs applied as soil amendment:
- Fresh/Raw Cattle Manure
The use of cattle manure, or cow dung, in agricultural production is a popular practice in many rural areas. This type of manure is not as rich in nitrogen as many other types; however, the high ammonia levels can burn plants when the fresh manure is directly applied. Raw Cow manure contains high levels of ammonia and potentially dangerous pathogens. For this reason, it’s usually recommended that it be aged or composted prior to its use as cow manure fertilizer(Usman, 2021) - Composted Cow Dung
Composted manure is decomposed animal feces that have been heated sufficiently through the composting process to remove harmful pathogens. Composted manure contains lots of nitrogen and is also a good source of other nutrients like phosphorous and potassium. Composted manure is preferred by many organic vegetable growers because composting reduces potential health and environmental risks of applying raw manure, and the compost contributes to more long-term soil fertility and health (Buchanan and Gliesmann, 2022). - Co-Composted Cow Dung
. Co-composting is the controlled aerobic degradation of the organics using more than one material. Improvement of cow manure by co-composting with other materials is beneficial to the quality of the amended soil (Oroka and Urueigho, 2019)
2.4 Effects of Biochar and Cow dung on Soil Chemical Properties
Soil chemical properties are those soil properties which are responsible and take part in the chemical reactions and processes of the soil . They are the results of weathering of soil mineral components, decomposition of organic materials, the activities of plants and animals pertaining to plant, animal growth and human development (Kimmins, 2021).
2.4.1 Soil Reaction
Soil reaction (pH) is the degree of soil acidity or alkalinity, which is caused by particular chemical, mineralogical and/or biological environment (Shehu et al, 2019). It is the simplest and the most important chemical parameter measured in soils Teferi (2018). It has vital role in determining several chemical reactions. It influences plant growth by affecting the activity of soil microorganisms and altering the solubility and availability of most of the essential plant nutrients and particularly the micronutrients such as Fe, Zn, Cu and Mn (Miller and Donahue, 2020; Rao, 2020).
Descriptive terms commonly associated with certain ranges in pH are extremely acidic (pH <4.5), very strongly acidic (pH 4.5-5.0), strongly acidic (pH 5.1-5.5), moderately acidic (pH 5.6-6.0), slightly acid (pH 6.1-6.5), neutral (pH 6.6-7.3), slightly alkaline (pH 7.4-7.8), moderately alkaline (pH 7.9-8.4), strongly alkaline (pH 8.5-9.0), and very strongly alkaline (pH > 9.1) (Fothand Ellis, 2021).
The study of Nabahungu, (2021) showed that the soil pH can also be significantly increased by adding organic residues into the soil. This is attributed to higher concentrations of basic nutrients in organic amendments and hydrous oxides reduction in soils. Plants can only use nutrients that are in an inorganic form. Manure N and P are present in organic and inorganic forms, and are, therefore totally unavailable to plants. The organic forms must be mineralized or converted into inorganic forms over time before they can be used by plants.
The research findings of Ayni and Adeleye (2021) soil samples treated with 5 t ha-1 cattle dung increased soil pH but at different rates of increment. Their study also showed that cattle dung applied without urea fertilizer significantly increased soil pH while there was slight reduction in pH level of the soil fertilized with urea alone in the soil samples. Their findings showed that cow dung can increase the pH of soils. Adeniyan et al. (2018) obtained similar result in an experiment conducted on comparative study of different organic manures and NPK fertilizers for improvement of soil chemical properties . The increase in pH as a result of applying cow dung to soil might be as a result of cations especially Ca3+ present in cattle dung (Babalola et al., 2012).
2.4.2 Available Phosphorus
Phosphorus (P) is known as the master key to agriculture because lack of available P in the soils limits the growth of both cultivated and uncultivated plants (Foth and Ellis, 2021). Following Nitrogen, Phosphorus has more wide spread influence on both natural and agricultural ecosystems than any other essential elements. Phosphorus is rarely found in the pure elemental form (P) in nature. It is chemically very reactive; thus, it is almost always found combined with other elements, Fe, Mn, and other elements to form insoluble compounds that are only slowly available to plants. Phosphorus must be managed very carefully to maximize its availability to plants. Available soil P is derived from the weathering of a number of different minerals, but primarily from the chemical breakdown of apatite, which is composed largely of calcium phosphate (Brady and Weil, 2012).
Manure increases also P in the soil . The manure requirements for most of the crops are high, ranging from 5 to 20 tons of fresh manure per ha-1 . Manure, when applied, will be mineralized gradually and nutrients become available (Zheng, 2019)
2.4.3 Cation Exchange Capacity
Cation exchange capacity (CEC) of the soil is defined as the sum of the positive charges of the cations that a soil can absorb at a specific pH value. In other words, it is the sum of the positive charges of all of the adsorbed cations (Miller and Donahue, 2020; Rai, 2020). The cation exchange capacity (CEC) of soils is stated as, the capacity of soils to adsorb and exchange cations (Brady and Weil, 2012).
The CEC of a soil is strongly affected by the amount and type of clay, and amount of OM present in the soil (Curtis and Courson, 2018). Both clay and colloidal OM are negatively 23 charged and therefore can act as anions (Kimmins, 2021). As a result, these two materials, either individually or combined as a clay-humus complex, have the ability to absorb and hold positively charged ions (cations). Soils with large amounts of clay and OM have higher CEC than sandy soils low in OM. In surface horizons of mineral soils, higher OM and clay contents significantly contribute to the CEC, while in the subsoil particularly where Bt horizon exist, more CEC is contributed by the clay fractions than by OM due to the decline of OM with profile depth (Foth, 2018; Brady and Weil, 2012). Soil solutions contain dissolved chemicals, and many of these chemicals carry positive charges (cations) or negative charges (anions) (Fisher and Binkley, 2018). Cation exchange is considered to be of greater importance to soil fertility than anion exchange, because the he majority of essential minerals are absorbed by plants as cations (Poritchett and Fisher, 2021).
The nutrients required for plant growth is present in the soil in a variety of forms (Kimmins, 2021).They may be dissolved in the soil solution, from where they can be utilized directly. They may be absorbed onto exchange sites, from where they inter soil solution or be directly exploited by tree roots or microorganisms that come in contact with the exchange site. Alternatively, they may be firmly fixed in clay lattices, immobilized in decomposition resistant OM, or present in insoluble inorganic compounds. An exchangeable cation is one that is held on a negatively charged surface and displaced by another cation. The exchangeable cation is a desirable form of a nutrient being quickly brought into solution and made accessible to roots by the exchange with proton. Although the cation nutrients held on the exchange sites form a readily available pool, they do not represent the cation supplying ability of the soil (Binkley and Sollins, 2018; Binkley et al., 2012).
2.4.5 Soil Organic Matter, Nitrogen and C:N Ratio
Soils are characterized as mineral or organic, on the basis of OM content. Mineral soils form most of our cultivated land and may contain from a mere trace to 20 to 30% OM, but organic soils contain 80% or more OM (Prasad and Power, 2021). Soil OM controls many soil physical and chemical properties. It improves aggregate stability, structure of soils and is a source of several essential plant nutrients, especially N, S and P (Prasad and Power, 2021).
Zhang et al. (2019) found that 2 kg manure-N were equivalent to 1 kg of urea-N in terms of plant uptake and yield response during the first year following cattle feedlot manure application. The research findings of Onwuka and Ifedube (2019) corroborated that of Zheng et al (2019) as it showed showed that an application of biochar increased the nitrogen content of soils.
Animal manure compost can increase the bacteria and fungi diversity due to increasing carbon pool of the soil (Hoorman and Islam 2018; Zhen et al., 2019). As the carbon pool is increased, the living condition of the indigenous microbial are increased.
The study of Ndor et al (2020) showed that there were significant differences in total quantity of carbon sequestered at the different rates of biochar application. Application of 10t/ha sequestered a largest quantities of 1352.40 t/ha of soil organic carbon. The lowest carbon stored of 926.85 t/ha was reported in control plot. The findings of Ndor et al (2020) was supported by the assertion of Gaunt and Lehmann (2018) who noted that one of the major benefit associated with the use of biochar as a soil amendment is its ability to sequester carbon from the atmosphere and transfer it into the soil thereby mitigating climate change . Cheng (2018) further predicted that the biochar storage capacity of global cropland and temperate grassland is going to be 400Gt C, which would be equivalent to 25% increase in global soil carbon. Downie (2019) added that biochar may persist in soil for millennia because it is highly resistant to microbial decomposition and mineralization. However, this particular characteristic of biochar depends strongly on its properties.
2.4.6 Exchangeable Acidity
Exchangeable acidity refers to the sum of the concentrations of hydrogen (H) and aluminium (Al) ions in the soil exchange complex, and is inversely related to base saturation and pH of the soil. For instance, exchangeable Al does not commonly occur in an appreciable quantity in soils with pH values above 5.5 Teferi (2018). Soil acidity occurs when acidic H+ ion occurs in the soil solution to a greater extent and when an acid soluble Al3+ reacts with water (hydrolysis) and results in the release of H+ and hydroxyl Al ions into the soil solution (Rowell, 2019; Brady and Weil, 2012). When the soils become strongly acidic, they may develop sufficient Al in the root zone and the amount of exchangeable basic cations decrease, solubility and availability of some toxic plant nutrient increase and the activities of many soil microorganisms are reduced, resulting in accumulation of OM, reduced mineralization and lower availability of some macronutrients like N, S and P and limitation of growth of most crop plants (Rowell, 2019) and ultimately decline in crop yields and productivity (Miller and Donahue, 2020; Tisdale et al., 2020; Foth and Ellis,2021; Brady and Weil, 2012). Foth and Ellis (2021) stated that during soil acidification, protonation increases the mobilization of Al and Al forms serve as a sink for the accumulation of H+.
The research findings of Ayni and Adeleye (2021) Al3++H+ was slightly reduced due to the addition of 5 t ha-1 of cattle dung in the soil samples collected from the four ecological zones in Nigeria while urea fertilizer applied alone significantly increased Al3++H+. Their study further showed that single application of cattle dung reduced Al3++H+ by 0.1 while cattle dung combined with urea fertilizer reduced it by 0.2. The findings of Ayni and Adeleye (2021) is similar to the assertion of Onwuka and Ogbonna (2019) who noted that that the basic cations present in organic wastes displaced the acidic cations from the soil exchangeable complex by neutralization and precipitation thereby increased soil pH with corresponding decrease in EA.
2.4.7 Exchangeable Basic Cations of Potassium and Sodium
Soil parent materials contain potassium (K) mainly in feldspars and micas. As these minerals weather, and the K ions released become either exchangeable or exist as adsorbed or as soluble in the solution (Foth and Ellis, 2021). Potassium is the third most important essential element next to N and P that limit plant productivity. Its behavior in the soil is influenced primarily by soil cation exchange properties and mineral weathering rather than by microbiological processes. Unlike N and P, K causes no off-site environmental problems when it leaves the soil system. It is not toxic and does not cause eutrophication in aquatic systems (Brady and Weil, 2012). Wakene (2018) reported that the variation in the distribution of K depends on the mineral present, particles size distribution, degree of weathering, soil management practices, climatic conditions, degree of soil development, the intensity of cultivation and the parent material from which the soil is formed.
The availability of K in manure is considered similar to that in commercial fertilizer since the majority of K in manure is in the inorganic form. In general, 90 to 100 % of K in manure is available during the first year of application.
The result of soil properties under different biochar treatment sampled after two years of maize cropping showed that biochar application had a significant effect on all the chemical properties of the soil except on sodium (Ndor et al, 20185)
2.5 Amaranthus Spinosis
Amaranthus spinosus Linn are erect, monoecious perennial, up to 1 m. Stem are terete or obtusely angular, glabrous or slightly pubescent, green, reddish-brown, glabrous, and branched. The leaves alternate and are simple without stipules; petiole is approximately as long as the leafblade16-17.The blade shape is ovate-lanceolate to rhomboid, acute and often slightly decurrent at base, obtuse, rounded or slightly ret use and often short mucronate at apex, entire, glabrous or slightly pubescent on veins when young18-19 . The inflorencence are terminal and axillary, spike-like, erect, slender and elongated, with remote axillary spikes at base, lower clusters, pistillate, upper staminate.
The crop is adapted to a wide range of soil conditions. Sandy soil with slight acidity is best suited. A temperature range of 20-300C is required for better vegetative growth. The land should be ploughed or dug followed by leveling then shallow trenches of width 30 - 35cm well rotten farm yard manure is mixed with soil in the trenches. (Costea and Demason, 2018). Amaranth is planted either by direct seeding or transplanting. The choice of planting method depends on availability of seed and labor and may also vary with growing season. Direct seeding is appropriate when plenty of seeds is available, labor is limited and during the dry season when frequency of watering is less. Transplanting is preferred when there is limited amount of seed, plenty of labor and during the wet season when heavy rains and flooding are most likely to wash out the seeds. When direct seeding is used, seeds are either broadcast or sown in rows on wellprepared seedbeds. Broadcast seeds uniformly at the rate of 0.5 to 1.0g/m2 bed; there are about 1000 amaranth seeds per gram. Since amaranth seeds are very small, mix seeds with sand at a ratio of 1g seed to 100g sand to make it easier to sow the seed and obtain a uniform stand, cover seed lightly with a layer of compost or rice hulls immediately after broadcast (Costea and Demason, 2018).
It is highly adapted under lowland condition. Grow well at day temperatures above 250C and night temperatures not lower than 150C. Amaranthus are quantitative short day plants. It consumes high amount of water and uses 6 mm/day. Amaranth prefers fertile, well drained soils with a loose structure. (Aletor and Adeogun, 2020).
2.6 Effects of Cow dung and Biochar on Growth Performance of Plants
The research findings of Adekiya et al (2020) showed that there was increase in growth and yield parameters of maize in response to the application of cow dung and could be adduced to the fact that cow dung contains nutrients and these nutrients are released to the soil for maize plant compared with no application of cow dung. The study further observed that the best performance of maize under 10 t/ha cow dung was due to better soil condition resulting from this treatment.
Also Onwuka and Ifedube (2019) noted that application of biochar significantly increased the soil properties and Greenleaf growth of Amaranthus. Washa et al (2020) after his study concluded that cow manure not only increase maize production significantly but also supports the production of soil microbial and hence renewals the soil minerals and soil fertility as well.
CHAPTER THREE
MATERIALS AND METHODS
3.1 Study Area and description
A pot trial was conducted at the Greenhouse of College of Crop and Soil Sciences, Michael Okpara University of Agriculture Umudike (latitude 05°29N and longitude 07°33E). Umudike. It has an elevation of 122 m above sea level, with mean rainfall of 2117 mm, distributed over nine to ten months in a bimodal rainfall pattern starting from April to July and August to October. The monthly minimum air temperature at Umudike ranged from 20 °C to 24 °C while the monthly maximum air temperature ranged from 28 °C to 35 °C. The geology of the study area is sedimentary to the formation of coastal plain sand. The agricultural land use is arable crop production (Source: NRCRI Umudike Meteorological Station, 2020).
- 2 Treatments and treatment preparations
The treatments comprised of four amendments and a control namely: Composted Cow dung (CCD), Co-composted biochar and cow dung (CBC), Composted Cow dung and biochar mixed after composting (CMB), biochar (B) a control that will not receive any amendment (Ctrl). . The treatment layout is shown on Table 1 below. The cow dung was collected from the Livestock of Michael Okpara University of Agriculture Umudike. Composted Cow dung was prepared by composting in a composter for ninety (90) days. At the end of the ninety days, maturity test of the compost using the earthworm test and seed germination test was conducted to ascertain the maturity of the of compost. Then the matured compost was air dried, crushed and passed through a 2 mm sieve mesh. Biochar was produced with mungbean pod waste as the feed stock. The feed stock was subjected to pyrolysis using a 210 litre capacity pyrolysis drum with temperature at an approximate of about 450°C. About 10 kg of the feedstock was subjected to pyrolysis and allowed to be heated for 4 hours (Onwuka et al., 2019); afterwards the biochar was allowed to cool for 24 h by sprinkling water. The biochar was thoroughly mixed and ground to pass through a 1mm sieve mesh.
3.4 Soil Sampling and Experimental procedure
The soils was randomly sampled from some locations at the Eastern Farm of Michael Okpara University of Agriculture at the depth of 0- 15 cm. The samples were bulked to get a composite sample that was taken to the soil preparation room. The soil samples were air dried, at room temperature and passed through a 2 mm sieve mesh, before using for the experiment.
Each pot of twelve litre capacity will receive 10 kg of the composite sample. The amendment was applied on a dry weight basis at the rate of 1.4 kg (equivalent to 5 t ha-1) to 10 kg of soil (Onwuka et al., 2019). The amendments were randomly applied to the soil and thoroughly mixed together. The treatment was randomized in the experimental pots and replicated three times in a Completely Randomized Design. The study was of composed of total of fifteen (15) experimental units.
3.5 Test crop and Nursery preparation
Greenleaf Amaranthus (Amaranthus caudatus) was the test crop: The seeds used for the study were sourced from the open market at Enugu town in Enugu State. The variability of the seed was determined by the germination test of the seeds. If 70% of the seeds germinate then it was assumed to be variable for planting. Greenleaf seeds was seeded into the nursery containers made of wooden material. The length, width and depth of the containers was 90 x 60 x 30 cm respectively. These were filled with a mixture of loamy soil, manure, and river sand, in a ratio of 3:2:1. The seedlings were transplanted to the pots after two weeks of being raised in the nursery. They were planted four per pot and then thinned down to two per pots after two weeks of transplanting.
3.6 Laboratory Analysis State all the analyses were conducted.
Particle size distribution
Particle size analysis was determined by the standard hydrometer method (Gee and Bauder, 1986) which involved the dispersion of soil particles with sodium hexametaphosphate (Calgon). Fifty gram of sieved soil was weighed into polythene bottle, 100 mls of Calgon solution was added into the bottle. The mixture was placed on a mechanical shaker and agitated for 15 minutes. The soil suspension was transferred into 2 litre capacity cylinder and diluted up to the 1 litre mark with water. The suspension was stirred with a plunger before inserting the hydrometer. The hydrometer readings after 40 seconds were recorded for determining silt and clay content. Reading after 2 hrs were recorded and used to determine the proportion of clay fraction alone. The temperature and hydrometer reading for the blank were recorded. Computations were carried out for the particle size fractions using a formulae below.
% clay=
% Slit =
% Sand = 100- (% clay +silt)
Corrected reading (C) = R-B ± (0.36T)
C = corrected reading
R = uncorrected reading
B = Blank
T = Temperature of suspension
Textural triangle was used to determine the textural classes (United State Department of Agriculture (USDA), 1951)
Soil pH was determined in 1:2.5 soils to water ratio respectively using a glass electrode pH meter (Mclean, 1986). pH of the soil sample was determined using a 1:2.5 soil water ratio using glass electrode by (Udo et al.,2009). Ten gram (10g) of soil was weighed into a beaker and 25ml of distilled water was added to the soil. The suspension was stirred occasionally with glass rod for 10minutes and was allowed to stand for about 30minutes. Thereafter the electrode of the pH meter was inserted into the partly settled suspension and the pH of the sample was measured by taking the reading of the pH meter.
Organic carbon was determined using the wet oxidation method of Walkley and Black as described by Nelson and Sommers (1986).
Total nitrogen was determined using the macro-kjedahl method of Bremmer and Mulverney as described by Jackson (1962).
Available phosphorus was determined by Bray 1 method as described by Bray and Kurtz (1945).
Exchangeable cation (K, Na, Ca and Mg) was extracted with 1N ammonium acetate (NH4OAc) buffered at pH 7, afterwards sodium (Na+), and potassium (K+) were read using flame photometer, while magnesium and calcium was determined using the ethylenediamine tetracetic acid (EDTA) titration method as described by Page, et al.,(1982).
Exchangeable acidity was determined by the method of Mclean (1986) as outlined by Udo, et al., (2019).
Effective cation exchange capacity was calculated as the sum of exchangeable basic cation (calcium, magnesium, potassium and sodium) and exchangeable acidity expressed in cmolkg-1. Percentage base saturation was obtained by calculation using the formula below:
% Base saturation = X 100
3.9 Statistical Analysis
The data generated was subjected to Analysis of Variance (ANOVA) for Completely Randomized Design (CRD) using the GENSTAT package (19th Edition). The means were separated using the Fisher’s Least Significant Difference (LSD). Also correlation and regression analysis was conducted using the same statistical package (17thEdition).
CHAPTER FOUR
RESULTS AND DISCUSSION
4.1 Physiochemical Properties of Pre-Treated Soils
Physiochemical Properties Of Pre Treated Soils is as shown in table 4.1
The particle size distribution of the soil showed that the value of sand was 798g/kg while that of silt and clay were 108g/kg and 94g/kg respectively. The soils are of high sand content and textural class is Loamy Sand. Similar findings were observed by Onwuka and Igwe (2010) in soils of Umudike. Osujieke et al (2018) noted that Soils with high sand content are associated with nutrient leaching, high infiltration and infertility hence the need for soil amendment for sustainable crop production.
The pH (H2O) and pH(Kcl) values were 5.1 and 4.0 respectively. The soil was sandy loam, having a pH of 4.0 and 5.1 signifying strong acidity (Hazelton and Murphy, 2011). The findings on the pH of the soil is similar to that of Akinmutimi and Azubuike (2019) as they observed that soil within Umudike was acidic. Chukwu et al (2013) noted that the acid nature and poor nutrient statuses of the soils could be attributed, partly, to the sedimentary parent materials-Shale, Coastal Plain Sands and Colluvial Sands- which had undergone earlier cycles of pedogenetic and erosional history before deposition
The Electric conductivity and Available phosphorous content were 0.40 µ and 13.8 mg/kg. The nitrogen content of the soils was 0.088% while that of Organic Carbon and Organic matter were 0.98% and 1.69% respectively. The Calcium and Magnesium values were 3.20cmol/kg and 1.30cmol/kg respectively and that of Potassium and Sodium were 0.118cmol/kg and 0.150cmol/kg respectively.
Fertility indices showed that the soil was acidic and low in fertility. This confirms earlier works (Onweremadu et al., 2007; Onwwuka nd and Igwe, 2010; Emma et al, 2016; )which reported that soils in Rivers, Abia, Anambra and Imo states are characterized by low pH, low organic carbon and low exchangeable cations and bases. The low values of these chemical properties is a critical factor (Onweremadu et al., 2007.) militating against increased crop productivity thereby creating the need and demand for soil amendment.
Exchangeable Acidity content was 1.58cmol/kg Also, the percentage of Base Saturation was 75.12%.
Table 4.1, Physiochemical Properties of Pre-Treated Soil
Properties
value
Sand (g/kg)
798
Silt (g/kg)
108
Clay (g/kg)
94
Texture
Loamy sand
pH (H2O)
5.1
pH (kcl)
4.0
Electric Conductivity (µ)
0.40
Available phosphorous (mg/kg)
13.8
Nitrogen (%)
0.088
Organic carbon (%)
0.98
Organic matter (%)
1.69
Calcium (cmol/kg)
3.20
Magnesium (cmol/kg)
1.30
Potassium (cmol/kg)
0.118
Sodium (cmol/kg)
0.150
Exchageable Acidity (cmol/kg)
1.58
Aluminum (cmol/kg)
0.56
Effective cation exchange capacity (cmol/kg)
6.35
Base saturation (%)
75.12
4.2 Properties of Amendments Used
Sample
pH
(H2O)
EC
µ
P
(%)
N
(%)
OC
(%)
OM
(%)
Ca
(%)
Mg
(%)
K
(%)
Na
(%)
C/N
ratio
Composted Cow
Dung & Biochar
9.3
46.9
2.10
1.40
17.95
30.95
0.82
0.52
1.20
0.50
12.82
Cow dung
8.7
28.5
1.70
1.10
18.92
32.62
0.60
0.46
0.88
0.44
17.20
Biochar
9.6
34.0
1.88
0.72
18.79
32.39
0.80
0.44
1.10
0.40
26.09
Mix Cow dung & biochar
9.1
30.1
2.30
1.60
19.52
33.65
1.10
0.70
1.40
0.54
12.20
Result presented in table 4.2 shows that The pH, EC, P, N, OC, OM, Ca, Mg, K, Na and CN of the Composted Cow Dung & Biochar used in the study was 9.3, 46.9 µ, 2.10%, 1.40%, 17.95%, 30.95%, 0.82%, 0.52%, 1.20%, 0.50% and 12.82% respectively.
Also The pH, EC, P, N, OC, OM, Ca, Mg, K, Na and CN of the Cow dung was 8.7, 28.5 µ, 1.70%, 1.10%, 18.92%, 32.62%, 0.60%, 0.46%, 0.88%, 0.44% and 17.20% respectively.
Table 4.2 further shows that The pH, EC, P, N, OC, OM, Ca, Mg, K, Na and CN of the biochar was 9.6, 34.0 µ, 1.88%, 0.72%, 18.79%, 32.39%, 0.80%, 0.44%, 1.10%, 0.40% and 26.09% respectively.
Table 4.2 shows that The pH, EC, P, N, OC, OM, Ca, Mg, K, Na and CN of the Mix Cow dung & biochar was 9.1, 30.1 µ, 2.30%, 1.60%, 19.52%, 33.65%, 1.10%, 0.70%, 1.40%, 0.54% and 12.20% respectively.
4.3 Effect of Treatments On Chemical Properties Of Soil
Table 4.3 shows the effect of treatments (biochar alone, co-composited biochar and cow dung, composited cow dung , mixed composited cow dung and control ) on chemical properties of soil
Table 4.3: Effect of treatments on chemical properties of soil
Trt
…. pH ….
(H20) Kcl
EC
µ
Av.P
mg/kg
N
%
OC
%
OM
%
Ca Mg K Na EA ECEC
……………….. cmol/kg.………….……….
BS
%
Al3+
B
6.57
5.70
0.60
18.20
0.116
1.86
3.20
6.00
2.50
0.380
0.307
0.95
10.17
90.63
0.31
CBCD
7.2
6.27
2.10
24.97
0.217
2.23
3.84
8.80
3.80
0.430
0.383
0.53
13.91
96.16
0.16
CCD
6.83
6.00
0.65
16.60
0.170
1.95
3.35
6.60
2.80
0.360
0.314
0.87
10.95
92.03
0.26
MCDB
6.23
5.40
0.72
25.00
0.226
2.5
4.30
7.90
3.30
0.410
0.354
1.01
12.97
92.24
0.39
CTRL
4.60
4.03
0.33
11.80
0.067
0.81
1.35
2.70
0.80
0.074
0.107
2.02
5.70
64.55
0.74
Mean
6.30
5.48
0.88
19.31
0.159
1.87
3.22
6.41
2.60
0.332
0.293
1.08
10.74
87.12
0.38
LSD(0.0)
0.32
0.31
0.36
0.58
0.004
0.11
0.17
0.28
0.30
0.003
0.005
0.04
0.40
0.53
0.03
CCD: composted cow dung; CTRL: control; LsD: least significant difference; %: percentage; Av. P; available phosphorus; N%: Nitrogen; OC: organic carbon; Ca: calcium; K: potassium; Na: sodium; EA: exchangeable acidity; ECEC: effective cation exchange capacity; BS; base saturation; OM: organic matter
CRTL = No amendment added ; CCD= Composited cow dung; MCDB = Mixed composited cow dung and biochar; CBCD = Co-composited biochar and cow dung; B = Biochar alone
The pH(H2O) of the treatments were 6.57, 7.2, 6.83, 6.23, and 4.60 in biochar alone, co-composited biochar and cow dung, composited cow dung and biochar , mixed composited cow dung and control respectively. . Generally, there was an increase in soil pH(H2O) values of all the treatments except for control which had the significantly lowest pH(H2O) value of all the treatments. The soil of the control was more acidic than the pre-treatment soil. The highest significant (p < 0.05) value for pH(H2O) was obtained by the application of Co-composited biochar and cow dung. Also The pH(kcl) of the treatments ranged from 4.03 in control to 6.27 in co-composited biochar and cow dung . The pH(kcl) of the treatments was 5.70, 6.27, 6.00, 5.40, and 4.03 in biochar alone, co-composited biochar and cow dung, composited cow dung , mixed composited cow dung and control respectively. Generally, there was an increase in soil pH(kcl) values of all the treatments. The highest significant (p < 0.05) value for pH(kcl) obtained by the application of Co-composited biochar and cow dung. The findings of this study is similar to that of Onwuka and Igwe (2010) who observed that the application of organic amendments increased the soil pH.
The reason for the general increase of the soil pH by the application of Composited cow dung, Mixed composited cow dung and biochar;, Co-composited biochar and cow dung; and Biochar alone could be attributed to the high levels of basic cation which they contained. According to some researchers like Ano and Ubochi (2007) and Onwuka and Ogbonna (2009) animal manure and Biochar on analysis contain 17 - 27.60 cmol/kg of calcium and with a pH (H2O) of 6.7 - 11.9. The cations contained in these materials displaced the acidic cations like aluminum and hydrogen from the soil exchangeable complex by neutralization and precipitation Thereby increasing the soil pH
Electrical conductivity values ranged from 0.33µ in control to 2.10µ in Co-composited biochar and cow dung, The highest significant (p < 0.05) electrical conductivity was obtained by the application of Co-composited biochar while the significantly (p < 0.05) lowest electrical conductivity was observed in the control treatment.
The Av.P of the treatments were 18.20mg/kg, 24.97mg/kg, 16.60mg/kg 25.00mg/kg and 11.80mg/kg in biochar alone, co-composited biochar and cow dung, composited cow dung , mixed composited cow dung and control respectively. The highest Av.P(mg/kg) was observed in MCDB while the lowest Av.P(mg/kg) was observed in control
It was also observed that the Nitrogen content of the soils after treatment ranged from 0.116% in Control to 0.226% in mixed composited cow dung . The Organic carbon content of the treatments were 1.86%, 2.23%, 1.95%, 2.5% and 0.81% in biochar alone, co-composited biochar and cow dung, composited cow dung , mixed composited cow dung and control respectively. The highest organic carbon contents of the soils was observed after treatment with mixed composited cow dung while the lowest organic carbon content was observed in the control . The organic matter content of the soils were 3.20%, 3.84%, 3.35%, 4.30% and 1.35% after treatment with biochar alone, co-composited biochar and cow dung, composited cow dung , mixed composited cow dung and control respectively.
The application of the various treatments (biochar alone, co-composited biochar and cow dung, composited cow dung , mixed composited cow dung and biochar) significantly (p < 0.05) increased the available phosphorus, total nitrogen, organic carbon and organic matter over the control (Table 4.2). The result of the data obtained showed that the pots that received mixed composited cow dung and biochar gave significantly (p < 0.05) higher value for available phosphorus, nitrogen, organic carbon and organic matter among the various treatments in the study . It was observed that treatment with biochar gave significantly (p < 0.05) higher value for available phosphorus, nitrogen, organic carbon and organic matter than the control. This finding is consistent with that of Ndor et al (2014) who noted that biochar incorporation into the soil as soil amendment improved the both the physical and chemical properties of soil for crop production over the control. The study finding is also in conformity with the work of Lehman et al (2016) and Liang et al (2016) who reported that Biochar used as a soil amendment, can boost soil fertility and improve soil quality by improving cation exchange capacity (CEC), and retaining nutrients in soil.
It was also observed that the phosphorus, nitrogen, organic carbon and organic matter content of soils treated with biochar was significantly (p < 0.05) lower than that of co-composited biochar and cow dung, composited cow dung and mixed composited cow dung. Similar observation was made by Onwuka and Nwangwu (2016) and Adekiya et al (2016) . Onwuka and Nwangwu (2016) further posited that The significantly (p < 0.05) lower values of after treatment with biochar alone may be because these elements were volatilized in the course of producing the biochar. Nelissen et al., (2014) on the other hand noted that the relatively lower values of phosphorus, nitrogen, organic carbon and organic matter after treatment with biochar could be due to biotic N immobilization, reduced soil organic matter (SOM) mineralization, suppressed nitrification, increased gaseous losses or abiotic NH4 + and/ or NO3 − immobilization.
The improvement of phosphorus, nitrogen, organic carbon and organic matter in co-composited biochar and cow dung, composited cow dung and mixed composited cow dung is as a result of the presence of cow dung in the treatments which is adduced to increase soil organic matter (SOM) from the manure. The improvement in these properties could also be as a result of increased microbial activity associated with increased nutrient availability (Adekiya et al, 2016)
The Ca content of the treatments ranged from 2.70cmol/kg in control to 8.80cmol/kg in Co-composited biochar and cow dung . The highest significant (p < 0.05) value for Ca was obtained by the application of Co-composited biochar and cow dung . The Mg content of the treatments were 2.50cmol/kg, 3.80cmol/kg, 2.80cmol/kg, 3.30cmol/kg and 0.80cmol/kg in biochar alone, co-composited biochar and cow dung, composited cow dung , mixed composited cow dung and biochar and control respectively. The application of the various treatments significantly (p < 0.05) increased the Mg content of the soils over the control Furthermore, the K of the treatments was 0.380cmol/kg, 0.430cmol/kg, 0.360cmol/kg, 0.410cmol/kg and 0.074cmol/kg in biochar alone, co-composited biochar and cow dung, composited cow dung , mixed composited cow dung and biochar and control respectively. . Also, The Na ranged from 0.107cmol/kg in control to 0.383cmol/kg in Co-composited biochar and cow dung . The highest significant (p < 0.05) value for Na and K was obtained by the application of Co-composited biochar and cow dung. The findings of this study is similar to that of Onwuka and Igwe (2010) who observed that the application of organic amendments and ash led to increased Ca, Mg, K and Na of soils. Onwuka and Ihwe (2010) noted that The improvements recorded in exchangeable calcium, exchangeable potassium and exchangeable magnesium could be attributed to the fact that the treatments when added to the soil on decomposition and mineralization release the different nutrients in the soil.
The Exchangeable Acidity values ranged from 0.53cmol/kg in CBCD to 2.02cmol/kg in the control treatment. The Exchangeable Acidity values were 0.95cmol/kg, 0.53cmol/kg, 0.87cmol/kg, 1.01cmol/kg and 2.02cmol/kg in B biochar alone, co-composited biochar and cow dung, composited cow dung , mixed composited cow dung and biochar and control respectively. The applied treatments significantly (p<0.05) increased the soil pH value over the control with the Co-composited biochar and cow dung having the highest significant value. The reason for the general reduction in the soil exchangeable acidity, by the application of composited cow dung, mixed composited cow dung and biochar;, co-composited biochar and cow dung; and biochar alone could be attributed to the high levels of basic cation which they contained. According to some researchers like Ano and Ubochi (2007) and Onwuka and Ogbonna (2009) animal manure and Biochar on analysis contain 17 - 27.60 cmol/kg of calcium and with a pH (H2O) of 6.7 - 11.9. The cations contained in these materials displaced the acidic cations like aluminum and hydrogen from the soil exchangeable complex by neutralization and precipitation. Thereby reducing the exchangeable acidity
The ECEC of the treatments were 10.17, 13.91, 10.95, 12.97 and 5.70 in B, CBDB, CCD, MCDB and CTRL respectively. The highest significant (p < 0.05) ECEC was obtained by the application of Co-composited biochar and cow dung while the significantly (p < 0.05) lowest ECEC was observed in the control treatment.
The BS(%) of the treatments were 90.63%, 96.16%, 92.03%, 92.24% and 64.55% in B, CBDB, CCD, MCDB and CTRL respectively. The significantly highest (p < 0.05) base saturation value was observed after treatment Co-composited biochar and cow dung while The significantly lowest (p < 0.05) base saturation value was observed in the control The Al+ ranged from 0.16cmol/kg in Co-composited biochar and cow dung to 0.74cmol/kg in control
CHAPTER FIVE
CONCLUSION AND RECOMMENDATIONS
The constant utilization of the soil without proper amendment will lead to deterioration of w the soils as the control in the study had the highest soil acidity.
The amendment of soil using composited cow dung, mixed composited cow dung and biochar;, co-composited biochar and cow dung; and biochar alone caused an improvement in the soil properties by reducing soil acidity, increasing soil pH and increasing soil available nutrients such as soil available phosphorus, exchangeable calcium, exchangeable potassium, exchangeable magnesium, organic matter, total nitrogen and also increasing percentage base saturation
Among the various soil amendments tested, co-composited biochar and cow dung, mixed composited cow dung and biochar and Composited cow dung showed an overall best performance in improving quality of the soils under study. Further research is recommended for the field application of the treatments.