Research project
CHAPTER ONE
1.0INTRODUCTION
Soil fertility is an important form of renewable natural capital (Sanchez et al., 1997). A fertile soil which is productive results most often in yield increase giving profit to farmers (Fresco and Kroonenberg, 1992). Harsh climatic conditions, population pressure, land constraints, and the decline of traditional soil management practices result in decline of soil fertility (Tandon, 1998; Henao and Baanante, 1999). Agriculture is a soil-based industry that extracts nutrients from the soil. Therefore, effective and efficient approaches to slowing nutrients removal and returning of nutrients to the soil will be required in order to maintain and increase crop productivity and sustain agriculture for the long term (Gruhn et al., 2000). The maintenance of soil fertility involves the return to the soil of the nutrients removed from it by harvests, runoff, erosion, leaching, and other loss pathways (Aune, 1993).
The use of organic manure in farming has caught much attention lately (Ramesh et al., 2005). Manures from livestock and poultry are important ways of recycling nutrients into the soil. Sobulo and Babalola (1992), Ismail et al. (1996), Olayinka (1996) and Olayinka et al. (1998) have reported the use of several organic materials especially cow dung, poultry droppings, refuse compost and farmyard manure as soil amendments suitable for increasing crop production particularly among subsistence farmers in West Africa. However, the rate of nutrient release in organic manure is slow.
Inorganic/synthesized fertilizers are readily available and quick source of nutrients. The positive effect of the application of inorganic fertilizers on crop yields and yield improvements had been reported (Carsky and Iwuafor, 1999). Unfortunately, continuous and inappropriate use of inorganic fertilizer is harmful both to the soil and the environment. It affects the physical, chemical and biological quality of the soil. It increases soil acidity, and nutrient imbalance and pollution of underground water. It affects the activities of soil microorganisms and hence the soil organic carbon and organic matter content.
Soils harbour enormous microbial diversity including bacteria, archaea, fungi, insects, annelids, and other invertebrates as well as plants and algae. These organisms perform a large number of functions in the soil. For example, soil microbes play major roles in cycling carbon, nitrogen (N) and phosphorus. Heterotrophic bacteria and fungi are the ultimate recyclers of non-living organic material. These soil saprotrophs complete the carbon cycle, converting organic material formed by primary producers back to carbon dioxide during respiration (Aislabie and Deslippe, 2013) thereby improving the organic carbon and organic matter content of the soil.
SOC is the main component of soil organic matter (SOM). As an indicator for soil health, SOC is important for its contributions to food production, mitigation and adaptation to climate change, and the achievement of the Sustainable Development Goals (SDGs). SOC improves soil structural stability, it plays an important role in supplying plant nutrients, enhancing cation exchange capacity, improving soil aggregation and water retention and supporting soil biological activity (Dudal and Deckers, 1993). With an optimal amount of SOC, the water filtration capacity of soils further supports the supply of clean water (Lefèvre et al., 2017).
Organic and inorganic fertilizers applied to the soil supply plant nutrients for crop growth and affect the plant’s physiological processes, which serve as important instruments in yield development. Combination of pm with inorganic soil applied fertilizer has been extensively used on various crops to improve growth and yield. Mixing the two sources of fertilizer not only supply essential and micro nutrients for plant use, but also can have some positive interaction to increase their efficiency thereby reducing environmental hazards particularly soil pH (Bayu et al., 2006).
Maize (Zea mays L) is the most important and most widely distributed cereal in the world after wheat and rice. It is used for three main purposes: as a staple food crop for human consumption, a feed for livestock, and as raw material for many industrial uses, including bio-fuel production. Makinde and Ayoola (2001) observed that combined application of organic and inorganic fertilizer increased the yield of maize (Zea mays L.) than when any of the fertilizer was used alone. In a recent study on sweet maize (Z. mays L. var saccharata Strut), Uwah et al. (2011) reported that application of poultry manure at 10 t ha-1 mixed with 400 kg ha-1 NPK fertilizer out-yielded other treatments in biomass yield, harvest index and total grain yield. This study was therefore designed to investigate the effects of applications of inorganic fertilizer and soil amendments on organic carbon, root colonization, microbial population and yield of maize varieties.
1.1 JUSTIFICATION
Soil fertility is noted as a crucial problem facing agricultural development and food security in Sub- Saharan Africa (SSA) (Sanchez 2002). The steady decline in food production due to reduced length of fallow on land prompt farmers to amend the soil with different materials (organic and inorganic) in order to enhance plant growth and increase crop yield (Reijnties et al., 1992; Adepetu, 1997). Application of either organic or inorganic fertilizers or both to the soil not only affect the soil fertility, but it affects all the properties of soil. It is therefore necessary to investigate the effect of soil amendments on the quality of soil.
1.2 OBJECTIVES
1.2.1 Broad Objective
The aim of this research was to assess inorganic fertilizer and soil amendments on organic carbon, microbial activities and yield of maize varieties.
1.2.2. Specific Objective
The objectives of this research were;
To evaluate the effects of inorganic fertilizer and organic manure on organic carbon and microbial activities
To determine the effects of inorganic fertilizer and soil amendment on yield of maize
CHAPTER TWO
2.0LITERATURE REVIEW
2.1 FERTILIZER
The term "fertilizer/fertilizer material" means a commercial fertilizer containing one or more of the recognized plant nutrients, which is used primarily for its plant nutrient content. Fertilizers are derived from a wide variety of natural and manufactured materials and are sold in solid, liquid and gaseous form (anhydrous ammonia). These materials are designed for use or claimed to have value in promoting plant growth or increasing plant-available nutrient levels in soils (Agricultural extension service). They supplement the inherent soil fertility in order to bring about effective productivity. The value of a fertilizer material will depend on the amount of plant nutrients it contains and the availability of these nutrients to plants through the soil solution. Fertilizers can be inorganic or organic.
2.11 Inorganic/chemical fertilizers
Inorganic/chemical fertilizers are manufactured mixtures of chemical products that contain N, P, K and other necessary nutrients. Inorganic fertilizer exerts strong influence on plant growth, development, and yield (Stefano et al., 2004). Inorganic materials generally are relatively “high analysis” fertilizers with few impurities. Many of the more commonly used inorganic fertilizers are described below;
1. Nitrogen fertilizers: Inorganic N sources include ammonium and nitrate forms and urea.
Ammonium sulfate [(NH4)2SO4]: has been used in Hawaii for many years in both the sugarcane and pineapple industries as well as on small farms. It contains 21% N and 11% S. It will lower soil pH if used continuously over long periods of time.
Ammonium phosphates: Mono ammonium phosphate (MAP) [NH4H2PO4] supplies both N and P, at 11–13% N and 48–62% P2O5. Diammonium phosphate (DAP) [(NH4)2HPO4] is also widely used to supply both N and P, at 18–21% N and 46–53% P2O5. Both fertilizers are completely water soluble. Row or seed placement of DAP must be done with caution, especially in soils with high pH, because free NH3 can be produced, causing seedling injury. When these materials come in contact with soil in banded applications, MAP initially causes soil pH to be 3.5, while with DAP the pH is 8.0 (Tisdale et al., 1993).
Potassium nitrate [KNO3]: contains two essential nutrients, N (13%) and K2O (44%). It is not hygroscopic (that is, it does not pick up moisture from the air) so it is easy to apply, the NO3– is readily available, and it causes soil pH to increase slightly.
Calcium nitrate [Ca(NO3)2]: contains 15% N and 34% CaO. The NO3– is readily available, but the material is extremely hygroscopic. It is prone to liquefication if it is not stored in moisture-proof bags.
Urea [CO(NH2)2]: contains 45–46% N. It has very good physical properties in that it has less tendency to cake than ammonium nitrate and it is less corrosive than other N fertilizers. Its high concentration of N brings about savings in storage, transportation, handling, and application. Urea is soluble and can leach as readily as nitrate. However, once it has been converted to NH4+ and HCO3– in the soil by the enzyme urease, the NH4+ can be held on exchange sites and is thus less subject to leaching. Initially, urea can raise soil pH in the zone of application due to the release of NH3, but over time, soil pH can decrease from the original pH due to the nitrification of NH4+ to NO3–.
Sulfur-coated urea (SCU): is a controlled-release fertilizer that has a sulfur shell around each urea particle. The release of urea depends on the oxidation of the sulfur shell by soil microorganisms. The thickness of the sulfur shell can be varied to give different rates of release of urea. SCU contains 36–38% N and is useful in areas of porous soils with high rainfall or irrigation where NO3– can be leached readily. SCU also supplies S as it is oxidized by microorganisms (Tisdale et al., 1993).
2. Phosphorus fertilizers
Rock phosphate [Ca10OHF(PO4)6]: Rock phosphates contain apatite, which varies greatly in composition and solubility and becomes available to plants only in acid soils (pH <6.0). rock phosphates contain 27-41% P2O5, which is slowly available to plants but persists in the soil for many years. Applications of rock phosphate made by the sugar industry in the 1930s can still be detected by chemical extractants in some soils along the Hilo coast.
Superphosphates [Ca(H2PO4)2]: There are two types of superphosphates, single superphosphate (SSP) with 16–22% P2O5 and triple (or concentrated) superphosphate (TSP or CSP) with 44–52% P2O5 . Single superphosphate is made by treating rock phosphate with sulfuric acid, so it contains 11–12% S. Triple superphosphate, on the other hand, is made by acidulating rock phosphate with phosphoric acid, so it has only 1– 1.5% S. Phosphorus in both of these fertilizers is readily available to plants. These are neutral fertilizers, having little effect on soil pH (Tisdale et al., 1993).
Ammonium phosphates: Two forms of ammonium phosphate are monoammonium phosphate [NH4H2PO4], with 11–13% N, 48–62% P2O5, and 0–2% S, and diammonium phosphate [(NH4)2HPO4], with 18–21% N, 46–53% P2O5, and 0–2% S. Both are granular fertilizers that are completely water soluble.
3. Potassium fertilizers
Potassium chloride [KCl]: known as muriate of potash, contains 60–63% K2O and is completely water soluble. It is the most widely used potassium fertilizer. Potassium sulfate [K2SO4] is known as sulfate of potash and contains 50–53% K2O and 17% S. It is used on crops such as potato and avocado that are sensitive to large applications of chloride (Cl–). It is completely water soluble.
Potassium nitrate [KNO3]: supplies 44% K2O and 13% N. It is not very hygroscopic, is readily soluble, and increases soil pH.
Potassium-magnesium sulfate [K2SO4.2MgSO4]: sold as Sul-Po-Mag®, supplies 22% K, 11% Mg, and 22% S. It is widely used in dry fertilizer formulations.
4. Calcium fertilizers
Lime [CaCO3] and dolomite [CaMg(CO3)2]: are used as liming materials to adjust soil pH and supply calcium. Lime contains about 38% Ca, while dolomite contains about 22% Ca and 12% Mg. The amounts of Ca and Mg vary with the source of the material.
Calcium sulfate, gypsum [CaSO4.2H2O]: is an amendment supplying Ca in a form that changes soil pH very little, so it is useful in soils with adequate pH for plants. It contains 23% Ca and 19% S.
Calcium nitrate [Ca(NO3)2]: is highly soluble and supplies 15% N and about 20% Ca. It is useful where rapid calcium availability with a minimal soil pH change is desired (Tisdale et al., 1993).
Superphosphates: Single superphosphate supplies 18–21% Ca, while triple superphosphate supplies 12– 14% Ca. Thus, when superphosphate is applied to supply P to the soil, Ca is supplied also.
These formulations provide the opportunity to apply only the combinations of nutrients that are needed and thus make it possible to avoid overapplication of nutrients that are already adequate or in excess. It is necessary to identify the blend that best suits a particular purpose and costs the least per unit of nutrient (Tisdale et al., 1993).
2.12 Organic fertilizers
Organic fertilizers on the other hand are organic products which contains essential nutrients required for plant growth. The nutrients contained in the product are derived solely from the remains of a once-living organism. In general, organic fertilizers release nutrients over an extended period of time. They act much like the slow-release fertilizers. Potential drawbacks include the uncertainty of releasing enough of their principal nutrient at the proper time, costs, odors, commercial availability of the products and relatively low nutrient contents. Some products may also attract animals after application. Cotton-seed meal, blood meal, bone meal, fish emulsion and all animal manures are examples of these materials (Agricultural extension service). Animal manures are probably the most commonly available organic material used for their fertilizer value. Animal manures sometimes can’t be certified as an organic fertilizer because of some feed additives that might have been used to enhance animal performance. Animal manure is essentially a complete fertilizer. It varies in nutrient contents, but a fertilizer ratio of 1-1-1 is typical. Animal manures make outstanding soil conditioners. Commonly available manures include cow, swine and poultry. The highest nutrient values are generally found in the fresh manures and decreases as the material ages or is composted. Although fresh manures have higher available nutrient contents, an aged or composted material is sometimes more appropriately used to facilitate spreading, minimize burn potential or the presence of excess salts (Agricultural extension service).
Poultry manure contains all the essential plant nutrients that are used by plants. These include nitrogen (N), phosphorous (P), potassium (K), calcium (Ca), magnesium (Mg), sulphur (S), manganese (Mn), copper (Cu), zinc (Zn), chlorine (Cl), boron (B), iron (Fe) and molybdenum (Mo). The amounts of these nutrients can vary depending upon many factors including the age and diet of the flock, as well as the moisture content and age of the manure, diversity of soil microorganisms, particularly in sandy conditions. This effect enhances crop health by increasing water and nutrient availability, as well as suppressing harmful levels of plant parasitic nematodes, fungi and bacteria (Mohamed et al., 2010).
Types of poultry manure: there are different types of poultry manure such as deep litter manure, broiler manure, cage manure and high rise manure (Mohamed et al., 2010).
Deep litter poultry manure: This refers to the manure produced by layers during the laying period. Deep litter for laying hens usually consists of peanut hills, rice husk or wood shavings in a layer of 10-15cm deep. During the production, the accumulating manure gets mixed with the litter. When excreta are added, the litter becomes moist but remains aerobic. Aerobic fermentation occurs with the production of heat and loss of CO2 and ammonia (Simpson, 1986).
In this system, the poultry birds are kept in large pens up to 250 birds each, on floor covered with litters like straw, saw dust or leaves up to depth of 8-12 inches. Deep litter is the accumulation of the material used for litter with poultry manure until it reaches a depth of 8 to 12 inches. Suitable dry organic materials like saw dust, leaves, dry grasses, groundnut shells, broken up maize stalks and cobs, bark of trees in sufficient quantity to give a depth of about 6 inches in the pen should be used. The droppings of the birds gradually combine with the materials used to build up the litter (Mohamed et al., 2010).
Broiler house manure: This manure is similar to deep litter poultry manure but the litter is changed more frequently and there is less ammonia loss because of restricted decomposition. This results in manure richer in N than deep litter manure (Mohamed et al., 2010).
Cage manure: This manure contains 60-70% moisture since it is not mixed with litter materials. Litter is not used when birds are used in cages or slots. Enormous loss of ammonia occurs in this manure if it is not used the earliest. Two types of poultry cages viz, pyramid and stack type cages are in use. These are available in different standard sizes to meet the specific poultry producer’s needs. The pyramid-style layer cages come in 2, 3, 4 or 5 tier models, each model with a choice of automation features. These include: automated feed delivery, automated egg-gathering and automated manure removal. In the laying systems, each cage contains 1-25 birds and is suspended above a pit (Overcash et al., 1983).
Deep pit or high-rise manure: The deep pit solid manure system or high-rise building, has a concrete floor and masonry or concrete side walls and is typically constructed 2-6 feet below the ground. Pens or cages are then built on slotted flooring 8 feet or more above the pit floor. Because the pit is often built below ground level, care must be taken to insure that surface and ground water are not contaminated. Foundation drains and external grading to direct surface water away help to keep manure dry, so that natural composting might occur. High rates of air movement from mechanical fans located in the pit help to keep the manure relatively dry. A benefit of the deep pit system is that manure can be stored for several months before removal (Mohamed et al., 2010).
Nutrient content in poultry manure: The chemical composition of poultry manure vary because of several factors such as source of manure, feed of animals, age and condition of animals, storage and handling of manure and litter used (Mariakulandai and Manickam, 1975). Nutrient values of poultry manure vary considerably depending upon the conditions under which it is processed. The ratio of litter to manure and the moisture content causes considerable variation among manures from different houses. In fresh poultry excreta, uric acid or urate is the most abundant nitrogen compound (40-70% of total N) while, urea and ammonium are present in small quantities.
2.2 SOIL ORGANIC CARBON AND MICROBIAL ACTIVITIES
Soil organic carbon (SOC) is one part in the much larger global carbon cycle that involves the cycling of carbon through the soil, vegetation, ocean and the atmosphere. The SOC pool stores an estimated 1 500 PgC in the first meter of soil, which is more carbon than is contained in the atmosphere (roughly 800 PgC) and terrestrial vegetation (500 PgC) combined (FAO and ITPS, 2015). This phenomenal SOC reservoir is not static, but is constantly cycling between the different global carbon pools in various molecular forms (Kane, 2015). In principle, the amount of SOC stored in a given soil is dependent on the equilibrium between the amount of C entering the soil and the amount of C leaving the soil as carbon-based respiration gases resulting from microbial mineralization and, to a lesser extent, leaching from the soil as DOC. Locally, C can also be lost or gained through soil erosion or deposition, leading to the redistribution of soil C at local, landscape and regional scales. Levels of SOC storage are therefore mainly controlled by managing the amount and type of organic residues that enter the soil (i.e. the input of organic C to the soil system) and minimizing the soil C losses (FAO and ITPS, 2015). Factors controlling the decomposition of organic matter in soil include soil temperature and water content (mainly determined by climatic conditions) which greatly influence soil C storage through their effect on microbial activity. The composition of the microbial community (e.g. the bacteria:fungi ratio) may also have an influence on the preferential decomposition of certain compounds. The presumed chemical recalcitrance of complex molecules that build up SOC, such as lignin or lipids, does not substantially contribute to SOM persistence in soil (Marschner et al., 2008; Thévenot et al., 2010). SOM persistence is rather affected by SOC stabilization in the soil matrix through its interaction and association with soil minerals (Schmidt et al., 2011). Soil organic carbon plays an important role in supplying plant nutrients, enhancing cation exchange capacity, improving soil aggregation and water retention and supporting soil biological activity (Dudal and Deckers, 1993). It has been difficult to quantify the effect of SOC in crop and ecosystem productivity (Dudal and Deckers, 1993). Soil organic matter is not only a major regulator of various processes underlying the supply of nutrients and the creation of a favourable environment for plant growth but also regulates various processes governing the creation of soil-based environmental services (Vanlauwe, 2004). There are few reactions involving any component of the soil or of its biological inhabitants that are not sensitive to soil pH. This sensitivity must be recognized in any soil-management system (Brady and Weil, 1999). Soil pH can be affected by processes such as land use change, fire, and acid deposition (Islam and Weil, 2000; Certini, 2005; Lu et al., 2011). Soil acidity plays an important role in the nutrient cycle of soil and has some environmental aspects. Pichot et al (1981) reported from a ferruginous soil in Burkina Faso that with mineral fertilizer application, 25-50 % of the indigenous organic matter disappeared during first 2 years of cultivation. Pichot et al (1981) also observed that continuous cultivation using mineral fertilizers increased nutrient leaching, lowered the base saturation and aggravated soil acidification. Also exchangeable aluminium was increased and crop yield declined. Application of organic materials such as green manures, crop residues, or animal manure can counter the negative effects of mineral fertilizer (de Ridder and van Keulen, 1990). This led Pieri (1986) to conclude that soil fertility of soil under intensive arable farming in West Africa Semi-Arid Tropics (WASAT) can only be maintained through efficient recycling of organic material in combination with rotations of N2-fixing leguminous species and chemical fertilizers.
Soils are the foundation of all terrestrial ecosystems and are home to a vast diversity of bacteria, archaea, fungi, insects, annelids, and other invertebrates as well as plants and algae. These soil dwellers provide food or nutrients that support organisms that live above and below ground. Soil microbes; bacteria, archaea, and fungi play diverse and often critical roles in these ecosystem services (Aislabie and Deslippe, 2013). The vast metabolic diversity of soil microbes means their activities drive or contribute to the cycling of all major elements (e.g. C, N, P), and this cycling affects the structure and the functions of soil ecosystems as well as the ability of soils to provide services to people (Aislabie and Deslippe, 2013). Soils harbour enormous microbial diversity. The total fresh weight mass of organisms below temperate grassland can exceed 45 tonnes per hectare, equalling or exceeding above-ground biomass (Ritz et al., 2003). Bacteria are present in greatest numbers, with archaea 10-fold less. Estimates of the number of species of bacteria per gram of soil range from 2000 to 18000. Fungi, however, often contribute the largest part of the total microbial biomass in soils. The soil environment is very complex and provides diverse microbial habitats. Soils vary greatly depending on climate, organisms, land form, and parent material. Over time these factors interact so that soils develop characteristic horizons. Microbial activity in soil aggregates can influence oxygen distribution within soils, creating habitats for anaerobic microbes that catalyse a variety of soil processes such as methane production and denitrification. Within the soil aggregates most microbes adhere to the surface of soil particles, where they form. However, they are unevenly distributed and colonise only a small part of the available surface area. Organic matter and clay content of the soil are particularly important for determining the sorption of microbes to soil. Microbes exist throughout the soil profile; however, they are most abundant in surface soils, the rhizosphere of plants, and around macropores (Bundt et al., 2001; Fierer et al., 2007). Macropores are channels formed by plant roots, earthworms, and other soil biota and are often lined with organic matter. Both numbers and diversity of microbes are correlated with organic matter. Hence, soil microbial abundance and diversity are highest in the top 10 cm and decline with depth. Interestingly, Eilers et al. (2012) noted that bacterial composition was most variable in the surface horizons whereas lower down the communities were relatively similar. The taxonomic and functional diversity of soil microbes is influenced by the growth of plant roots, which locally modify the chemistry of soil in the rhizosphere by exuding carbon and excreting and adsorbing nutrients. In the rhizosphere plants allocate 1–22% of photosynthetic assimilate to their ectomycorrhizal fungus partner (Hobbie 2006), the mycelium of which represents a major route by which carbon flows between the plant and the soil microbial community. Carbon is released from the hyphae of the EM fungi as exudates like trehalose, mannitol or oxalic acid, and when hyphae senesce. Mycorrhizal root tips and the vegetative mycelium (the hyposphere) also provide a habitat for bacteria. In soils, microbes play a pivotal role in cycling nutrients essential for life. For example, soil microbes play major roles in cycling carbon, nitrogen (N) and phosphorus, which are essential for producing biomolecules such as amino acids, proteins, DNA and RNA – the fundamental compounds of life. Heterotrophic bacteria and fungi are the ultimate recyclers of non-living organic material. These soil saprotrophs complete the carbon cycle, converting organic material formed by primary producers back to carbon dioxide during respiration. They are sometimes aided in this process by higher animals (herbivores and carnivores) that digest particulate organic material with the help of microbes residing in their intestinal tracts. This process is known as decomposition and involves the degradation of nonliving organic material to obtain energy for growth (Aislabie and Deslippe, 2013). Mineralisation of the organic compound occurs when it is degraded completely into inorganic products such as carbon dioxide, ammonia, and water. In soil ecosystems, the major agents of organic matter decomposition are fungi, which constitute the majority of soil biomass. However, both bacteria and fungi degrade complex organic molecules that higher organisms cannot break down. A wide variety of bacteria, especially those belonging to Actinobacteria and Proteobacteria, degrade soluble organic molecules such as organic acids, amino acids, and sugars (Eilers et al., 2010). Microbes play an important role in the nitrogen cycle. They carry out several processes not carried out by other organisms, namely nitrogen fixation, dissimilatory nitrate reduction to ammonia (DNRA), nitrification, anammox, and denitrification. Because nitrogen is often the major limiting nutrient for plant biomass production in terrestrial habitats, the rates of these microbial processes often limit ecosystem productivity. Naturally occurring microorganisms – particularly bacteria and fungi biodegrade or detoxify substances hazardous to human health or the environment. These microbial processes are being harnessed for bioremediation (Aislabie and Deslippe, 2013).
Microbial activity reflects microbiological processes of soil microorganisms that include bacteria and fungi in different proportions depending on the soil system (Zhu et al., 2003). Soil microorganisms also process plant litter and residues into soil organic matter, which improves soil quality by increasing soil aggregation and aeration (Chen et al., 2003). Bending et al. (2004) observed that the size of the microbial biomass can be considered as an index of soil fertility and indicator of soil quality, which depends primarily on rate of nutrient fluxes (Singh et al., 2007), and quality and quantity of organic inputs determining the community structure (Peacock et al., 2001). At a gross level, an increase in microbial biomass is considered beneficial to the fertility of the soil, while its decline may be considered detrimental if this leads to a decline in biological function (CSIRO, 2011).
2.3 MAIZE (Zea mays)
Maize (Zea mays L) is the most important and most widely distributed cereal in the world after wheat and rice. It is used for three main purposes: as a staple food crop for human consumption, a feed for livestock, and as raw material for many industrial uses, including bio-fuel production. The name maize is derived from the Arawak-Carib word mahiz. It is also known as Indian corn, and in North America and Africa simply as corn (Purse-glove, 1976). It is one of the most utilized cereal in Nigeria. It is a grass of tropical origin that has become the major grain crop in the world in terms of total production, with recent production around 800 million tons per year. Most maize grain produced is used as animal feed; in less developed countries it is, however, also a staple food.
Maize originated under warm, seasonally dry conditions of Mesoamerica, and was by human selection converted from a low-yielding progenitor species into its modern form, with a large rachis (cob) of the female inflorescence bearing up to 1,000 seeds. Maize is a C4 plant and is very efficient in water use. If subjected to water stress, however, especially during the mid-season pollination process, yields can be much decreased. Crop management needs to be attuned to this moisture sensitivity, and planting date, cultivar and husbandry should be designed to minimize the chance of water shortage in the mid-season period (Nafziger 2010).
As a grain crop with high yield potential, maize needs an adequate nutrient supply, while the effects of weeds, insects, and diseases, especially during the reproductive period, should be minimized. Tillage is often performed before planting, but maize yields can be as high without tillage as they are with tillage; minimum or no tillage helps to conserve water while maintaining good yields (Nafziger 2010).
Planting rates need to be matched to the capability of the soil, and may range from less than 20,000 to more than 100,000 plants per hectare, depending on available soil water and nutrients (Nafziger 2010). Because of the ease with which maize grows and the fact that it does not require much of knowledge to plant, the number of its producers have increased. It is produced in large quantity on farms, and also in small scales even at backyards for family consumption. Maize yield is affected by biological factors such as diseases and pests, climatic factors such as rainfall and temperature and edaphic factors such as soil texture and soil structure. Maize require adequate water supply for optimum growth. They require water supply of about 600-900mm per annum at a temperature of between 20oC and 25oC. Furthermore, fertility of soil is another factor which influence yield of maize crops. Generally, the Nitrogen requirement of maize is always high. And so, when grown, maize crops are mostly supplied with nitrogen supplying fertilizers. Also, farmers intercrop maize with leguminous plants which fix nitrogen into the soil and so supply Nitrogen for maize.
Maize is a relatively exacting crop in terms of plant nutrients. It requires a large quantity of nitrogen (N), which is generally applied as a top dressing when the crop is 25-30 cm high. The nutrients removed by a yield of 4 t grain/ha are estimated at 200kg N/ha, 80 kg P2O5/ha and 160kg K2O/ha. In supplying the necessary nutrients for the crop, at least the same amount of these elements should be incorporated in the soil. The exact amounts of fertilizers to be added to the soil should be determined on the basis of soil analysis. Adequacy of supplies of nutrients can be assured by addition of nutrients in organic (animal or green manures) or inorganic (chemical fertilizers) forms (Nafziger 2010).
CHAPTER THREE
3.0MATERIALS AND METHODOLOGY
3.1 Experimental Site
The study was conducted at the Crop research farm, Directorate of University Teaching and Research Farms (DUFARMS), Federal University of Agriculture, Abeokuta, Ogun State, Nigeria with rainfall ranges of 120mm (May) to 195mm (September) and mean monthly temperature range of 22.50c – 33.70c. The relative humidity durning the rainy season (Late March – October) and dry season (November – early March) ranged between 63 – 96% and 55 – 84% respectively.
3.2 Land Preparation and Seed varieties
The land was ploughed, stumped afterwards and left for two weeks before second ploughing. Harrowing was done two weeks after ploughing to break the clods the experimental land area was mapped out and pegged after this operation.
The total plot is a 43.5m by 41m plot (1783.5m2). Forty eight 6m by 5m subplots was made in the plot. The inter-row spacing is 1m while the intra-row spacing is 0.5m. The maize varieties used are;
V1 = Open pollinated extra early matureV2 = Open pollinated early mature
V3= Hybrid early mature V4 = Hybrid extra early mature
3.3 Experimental design and procedure
3.3.1 Soil Analysis
Immediately after land preparation, soil samples were randomly collected from the experimental portion of the land at the depth of 0 – 15cm with the aid of soil auger to represent the top soil. The samples were mixed thoroughly, bulked together and sub-samples were taken for analysis to determine the pre-planting physico-chemical properties of the soil.
3.3.2 Sources of Seeds and Planting
Maize seeds were sourced from International Institute for Tropical Agriculture (IITA) Ibadan, Nigeria. Four varieties of maize were planted (TZE-WDT STR, ENT 12* TZEI 48, TZDEE 1* TZDEET 12 and 2013 TZEEW POPHDTSTR).
Germination test was carried out on the seeds to make sure they are viable. Planting was done afterwards. Direct sowing was done at 0.75m inter row and 0.25m intra row spacing.
3.3.3 Plot Management
Before planting, the plots were well labelled. After planting, the plots were well managed by ensuring that the inter-plots spaces were kept weed-free throughout the period of experiment. The plots were weeded manually twice at 4 and 8 weeks after planting.
3.3.4 Fertilizer Collection and Data Analysis
Nitrogen was source from inorganic fertilize (urea), poultry manure and swine dung. The poultry manure and swine dung that have been partially decomposed were collected from a livestock farm. Inorganic source (urea) was purchased from Ogun state Agro-services centre.
3.4 Data Collection
Five tagged plant stands within the net plot were used for growth parameters at 4, 6, and 8 WAP.
Leaf area (cm2): Leaf length * leaf breadth * 0.75 (Montgomery, 1911; Birch et al., 1998).
Leaf area index (LAI): Leaf area spacing (Watson, 1847).
100 grain weight (g): 100 grains was weighed using a sensitive scale.
Stem girth (cm): Vernier caliper was used to measure the diameter at the top, base and middle of the stem and the average was computed
Cob diameter (cm): This was determined using a Vernier caliper
Cob dry weight (g): Five cobs were measure using a sensitive scale.
Number of kernels per row: Numbers of seeds on a row were counted.
Number of kernels per cob: Numbers of seeds on a cob were counted.
Grain yield (kg/ha): Grains will be harvested from each net plot and weighed.
Dry matter measurement: Five random plants outside the net plot but not on the border rows was harvested and dried at 800c until constant weight is obtained at 2 weeks interval from 4WAP.
Plant height (cm): Height of the whole plant was measured with a measuring tape
Harvest index: Seed weight/total sample weight X 100. The sample weight is equal to the above ground weight
Shelling percentage (%): Seed weight/cob weight X 100.
3.5 Mycorrhizal studies
AMF root colonization and spore counting was determined.
3.5.1 Procedure of root staining, to observe mycorrhizal colonization
Roots will be preserved in 50% alcohol, then washed by rinsing in several changes in tap water. Then soaked in 10% KOH at 90°C for 30 minutes, the root was washed again in water to remove excess KOH. It was then be stained in acidic glycerol solution containing methyl blue lacto-glycerol solution (modified from Philips and Hayman, 1970) at 90 for 2 minutes, stain solution was discarded and roots was kept in acidic glycerol (without methyl blue). Colonization was determined by spreading the stained roots out evenly in grid plate then observe under a dissecting microscope.
3.6 Routine analysis
The following analyses were carried out on the representative soil samples taken from bulked soil samples from the experimental site.
3.6.1 Particle size analysis
The mechanical analyses of sand, silt and clay, was determined using Hydrometer method (Klute. 1987) with Calgon (sodium hexametaphospate) as dispersing agent. The mixture of soil sample and Calgon was left for 24hrs and later poured into a 1000m measuring cylinder and made up to the mark.
The first hydrometer reading was taken at 40secs after agitation for silt and clay.
Second hydrometer reading was taken after 2hrs for clay particles. Hydrometer reading of the blank was taken at each reading and temperature reading was taken separately.
The percentage of sand, silt and clay in the fraction are below
1st reading indicates silt and clay fraction
2nd reading indicate clay fraction
Silt - lst reading- 2nd reading
Since sand + silt + clay = 100
Sand = 100 - 1st hydrometer reading.
Calculation was done by (40secs reading-blank) + temperature
2hrs correction - 2(2hrs reading -blank) + temperature.
3.6.2 Soil pH
This was determined using glass electrode pH meter. Soil solution of 2:1 was use weighing 10g of soil into 20m1s of water. The solution was shaken with mechanical shaker for 30 mins at 250rev/min. the solution was allowed to settle for 25 mins before reading taken using electrode pH meter.
3.6.3 Soil Organic Carbon
The percentage of Organic Carbon was determined using Walkley Black method (1934).
One gram of 0.5mm sieved soil was weighed into a conical flask, lOmls of K2Cr07 would be added, swirled to mix and 20mls of Concentrated H2SO4 was rapidly added into the mixture. The flask was allowed to cool for 30mins and the solution was diluted 100mls of distilled water. 3 drops of ferroine indicator was placed in the mixture and it was titrated against 0.5N Fe (NH3)2(SO4)26H20 from a burette.
Appearance of maroon colour was indicate the end point. A blank titration with reagent with soil was done.
The percentage of Organic carbon was calculated thus:
Where B= Blank titre value. = sample titre value, 0.003= Milliequivalent of carbon (i.e 3/1000), 1.33= Correction Factor, 0.5N = Normality of FeSO4 that will be used.
3.7 Statistical Analysis
Data collected was subjected to Analysis of variance (ANOVA) using statistical analysis system (SAS, 2003) and the significant mean was separated using least significant difference (LSD) at 5% level of probability. Correlation analysis was carried out between growth and yield parameters.
CHAPTER FOUR
4.0 RESULTS AND DISCUSSION
4.1 Effects of inorganic fertilizer and soil amendment on growth and yield of maize varieties
Table 1 to Table 4 shows the effects of inorganic fertilizer and soil amendment on growth and yield of the maize varieties.
4.1.1 Effects of inorganic fertilizer and soil amendment on plant height
The effects of inorganic fertilizer and soil amendment on plant height is presented in Table 1. Effect of soil amendment on plant height of the different varieties was not significant at 4 and 8WAP, but it was highly significant at 6 and 10WAP. Open pollinated early maturing varieties had the highest height at 4WAP, but it outgrown by Hybrid extra early maturing varieties which had the highest height at 6, 8 and 10WAP. The effect of the different amendments on plant height was only significant at 10WAP. Plants on Urea amended soil had the highest height at 4WAP. At 6WAP, plants on poultry manure amended soil had the highest height. Plant height was highest in plants on swine dungs at 8 and 10WAP.
TREATMENTS
PLANT_HEIGHT
4WAP (cm)
PLANT_HEIGHT
6WAP (cm)
PLANT_HEIGHT
8WAP (cm)
PLANT_HEIGHT
10WAP (cm)
VARIETY
OPEE-
HE-
HEE-
OPE-
LSD
NS
25.43**
NS
19.12**
FERTILIZER
SD-
PM-
UREA-
LSD
NS
NS
13.68**
16.55*
VARIETY×FERTILIZER
NS
NS
NS
33.11*
Table 1: Effect of inorganic fertilizer and soil amendment on plant height
Figure 1: Effect of inorganic fertilizer and soil amendment on plant height of the maize varieties
4.1.2 Effects of inorganic fertilizer and soil amendment on leaf area
Table 2 shows the effects of inorganic fertilizer and soil amendment on leaf area. The effect of soil amendment on leaf area of the different varieties was not significant at 4WAP, but was significant at 6, 8 and 10WAP. The leaf area dropped at 10WAP in all varieties except for open pollinated early maturing. Hybrid extra early maturing varieties had the highest value for leaf area in 4, 8 and 10WAP, while Hybrid early maturing varieties had the highest leaf area in 6WAP. The effect of the amendments on leaf area was not significant in all the weeks. Plants on Urea amended soil had the highest leaf area in 4, 6 and 10WAP. The interaction between the varieties and fertilizers on leaf area was only significant at 8WAP.
Table 2: Effect of inorganic fertilizer and soil amendment on leaf area
TREATMENTS
LEAVE AREA
4WAP (m2)
LEAVE_AREA
6WAP (m2)
LEAVE_AREA
8WAP (m2)
LEAVE_AREA
10WAP (m2)
VARIETY
OPEE-
HE-
HEE-
OPE-
LSD
NS
112.8*
66.1**
76.5**
FERTILIZER
SD-
PM-
UREA-
LSD
NS
NS
NS
NS
VARIETY×FERTILIZER
NS
NS
114.5*
NS
Figure 2: Effect of inorganic fertilizer and soil amendment on leaf area of the different maize varieties
4.1.3 Effects of inorganic fertilizer and soil amendment on yield
Table 3 and 4 presents the effects of inorganic fertilizer and soil amendments on yield of maize. The effect of soil amendment on 100 grain weight, cob wet weight, grain yield, harvest index and number of kernel per row of the different varieties was not significant. Hybrid extra early maturing varieties had the highest 100 grain weight, harvest index and number of kernel per row, while Hybrid early maturing had the highest cob wet weight and grain yield. The effect of the amendments on 100 grain weight, cob wet weight, grain yield, harvest index and number of kernel per row of the different varieties was not significant. Poultry manure had the highest 100 grain weight and harvest index. Urea had the highest cob wet weight, grain yield and number of kernel per row.
Table 3: Effects of inorganic fertilizer and soil amendment on yield
TREATMENTS
%100 GRAIN WT (g)
COB WET WEIGHT(g)
GRAIN YIELD/Ha (kg/ha)
VARIETY
OPEE-
HE-
HEE-
OPE-
LSD
NS
NS
NS
FERTILIZER
SD-
PM-
UREA-
LSD
NS
NS
NS
VARIETY×FERTILIZER
NS
NS
NS
Table 4: Effects of inorganic fertilizer and soil amendment on yield
4.2 Effects of inorganic fertilizer and soil amendment on root colonization
The effects of inorganic fertilizer and soil amendment on root colonization is presented in Table 5. The effect of the soil amendments on root colonization in all the varieties is not significant. Root colonization varies among the varieties with Open pollinated early maturing having highest arbuscule; Open pollinated extra early having the highest hyphea; and Hybrid extra early maturing having the highest vesicle. The effect of the amendments on root colonization is not statistically significant. However, poultry manure brought about the highest arbuscule and hyphea colonization while swine dung had the highest vesicle colonization.
TREATMENTS
ARBUSCULE
HYPHEA
VESICLE
VARIETY
OPEE-
HE-
HEE-
OPE-
LSD
NS
NS
NS
FERTILIZER
SD-
PM-
UREA-
LSD
NS
NS
NS
VARIETY×FERTILIZER
NS
NS
NS
Table 5: Effects of inorganic fertilizer and soil amendment on root colonization
4.3 Effects of inorganic fertilizer and soil amendment on organic carbon
The effects of inorganic fertilizer and soil amendment on soil organic carbon is presented in Table 6. The effect of the soil amendments on soil organic carbon in all varieties is not significant. Hybrid extra early maturing had the highest organic carbon content at 4WAP. At 6 and 8WAP, organic carbon content was highest in Open pollinated extra early maturing varieties. Effect of amendments on soil organic carbon is only significant at 4WAP. Organic carbon was highest in Urea amended soils at 4WAP, while at 6 and 8WAP, it was highest in poultry manure amended soils. Interaction between variety and fertilizer on soil organic carbon was significant at 8WAP.
Table 6: Effects of inorganic fertilizer and soil amendment on organic carbon
4.4 Effects of inorganic fertilizer and soil amendment on soil pH
The effects of inorganic fertilizer and soil amendment on soil pH is presented in Table 7. The effect of soil amendments on soil pH in all varieties is not significant. Open pollinated extra early soils had the highest pH at 4WAP, however, at 6WAP, the pH of the soil reduced, hence, Hybrid early maturing soils had the highest pH value at 6 and 8WAP. Effect of amendments on soil pH was not significant. Soils amended with swine dung had the highest pH value in 4, 6 and 8WAP even though the pH reduced in the sixth week after planting.
Table 7: Effects of inorganic fertilizer and soil amendment on soil pH
Figure 3: Effect of inorganic fertilizer and soil amendment on soil pH
4.5 Effects of inorganic fertilizer and soil amendment on microbial population
The effects of inorganic fertilizer and soil amendment on microbial population is presented in Table 8. The effect of the different fertilizers and soil amendments on microbial population was not significant. Open pollinated extra early maturing varieties and poultry manure soils had the highest microbial population
Table 8: Effects of inorganic fertilizer and soil amendment on microbial population
CHAPTER FIVE
5.0 CONCLUSION AND RECOMMENDATION
5.1 Conclusion
Stefano et al. (2004), stated that inorganic fertilizer exerts strong influence on plant growth, development, and yield. The result of this study is in line with the conclusion of Stefano et al. (2004), as it had shown that growth and yield of maize is influenced by fertilizers. Growth and yield response of the different maize varieties to the treatments also varied. The growth and yield rate was not affected by the genetic variation among the varieties alone, it was also influenced by variations in the environmental factors.
Although, all the treatments gave an acidic soil after the experiment, the effects of the treatments on soil pH also varies. Urea favoured acidic pH most in all the treatments while Swine dung tend to increase the pH of the soil.
Organic carbon content of the soil varied among the maize varieties and was also influenced by the soil amendments. Open pollinated extra early maturing varieties and Swine dung improve the soil organic carbon content the most.
Root colonization is best favoured by poultry manure and hybrid early maturing variety. Microbial population is also highly favoured by poultry manure but unlike root colonization, open pollinated extra early maturing varieties gave the highest microbial population.
5.2 Recommendation
From the result of this study, I recommend that for maximum yield and productivity, farmers should plant Hybrid early maturing varieties and also use Urea at appropriate rate to supply required nutrients. However, to enhance the chemical (soil pH and soil organic carbon) and biological properties (root colonization and microbial population), I recommend that farmers plant open pollinated extra early maturing varieties in combination of swine dung and poultry manure.
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