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The future of humanity is at an important phase as the world population continues to increase at a high rate where food is deficient in supply in some regions of the world, while world grain reserves are at their lowest levels in 20 years. Increased population increases demand for food but also reduces the per capita area of land available for food and fiber production. As such there is very little area of land that can be used for agriculture for the production of food. Ironically, there is excessive food production in countries such as India and China. The avenues for exploring new technologies for increasing food production in developed countries have not yet been explored.
Nowadays, fertilizers are perceived as a source of pollution by many rather than an input for increased production of food and consequently providing for food security. The flow of nutrients through ecosystems is a normal process but this process is accelerated when the land is used for agricultural purposes, as there is movement of crops from fields to places where these are consumed. Hence the most economical way of boosting nutrient levels in the soil is to use mineral fertilizers. However the use of organic fertilizers and the reuse of nutrients in crop residues are very important practices in keeping the long-term fertility and productivity of the soil.
Malthus (1798) supported the fact that the balance of a food supply in a static position and with food demands increasing at a rapid rate could only be met only by decreasing the population through famine, disease, and war. Food production requires inputs such as fertilizers either in the organic or inorganic form to compensate for nutrients lost in harvested crops. The lack of knowledge on how to maintain soil fertility has caused the collapse of many thriving societies. (Ponting, 1990).
The advent of mineral fertilizers have decreased drastically the cost of transportation and labour necessary to replace nutrients lost through the practice of agriculture.(Baanante ,Bumb, and Thompson, 1989; Pinstrup-Andersen, 1993).
1.3 History of the fertilizer industry.
The history of the fertilizer industry started as early as man began started to practice agriculture as a means to meet his food requirements. Before this change in man was a hunter gatherer and therefore had to rely on gathering whatever forms of food he could find. Through trial and error people learnt that addition of manure, compost; ashes and other substances would give significant increases in yield. (Fertilizer Manual 1998). From past experiences, it has been shown that chemical fertilizer is one of the most important productivity boosting input. (Onuwaka, 2005).
1.4 Foundations for the modern fertilizer industry.
The foundations for the modern fertilizer industry are considered to have been laid down by Justus Von Liebig. He highlighted the importance of mineral elements in plant nutrition. He identified that nitrogen is an important element in the nutrition of plants. His vision of the fertilizer industry was that phosphate, lime and magnesia being produced in chemical factories and also suggested the reaction of bones with sulphuric acid to produce phosphate which could be made readily available for uptake by plants. (Fertilizer Manual 1998).
1.5. The Fertilizer Era
When plant scientists felt the necessity for N fertilizers, they were searching for sources which could be used as fertilizers. The first one was guano, the bird droppings that were deposited on shores but were depleted by 1890. (Smil, 2001). It was evident that these deposits would not last forever hence the industrial production of nitrogen became necessary. The processes that were used were far too inefficient and energy consuming and the methods were as follows:
Coking of coal
High temperature synthesis of cynamide
Nitrogen fixation by electrical discharge.
However, these processes could not meet the needs of developing agriculture. However the invention of the Haber-Bosch process is probably one of the important developments in the 20th century as without this invention it would have been impossible to produce food at a global level. According to Smil (2001), synthetic fertilizer is the source of nutrients for over half of the nutrients available to annual and permanent crops.
1.6 Overview of fertilizer industry from the year 2003-2008.
Mauritius imports its fertilizer mainly from the following countries: Israel, South Africa, Egypt, Australia, China, India, and Belgium. (Anon, 2002).
The consumption of fertilizers has decreased in the year 2002 from 64739 to 48109 tonnes in 2006.This represents a decrease of about 30%. The same can be said about the nutrient contents imported which has experienced a decrease of 22% in the case of nitrogen, 15.4% in the case of phosphorus and 32.5% in the price of potash.
Table 1.6.1 shows the consumption of fertilizers from the year 2002 to 2006
Source: Central Statistics Office (Quantity in tonnes, c.i.f value in Rs '000)
1.7 Price of fertilizers from the year 2005 to 2008
The price of fertilizers has increased considerably during this period (Digest of Agricultural Statistics 2008). Farmers have started to use less and less fertilizers in their fields as supported by the trend in the consumption of fertilizers. The price of fertilizers has increased significantly from the year 2002 to the year 2006. (Table 1.6.2).For example the price of muriate of potash has experienced an increase of 222%. Bumb (2008) states that farmers in developed countries are using greater amounts of fertilizers to improve yields which are leading to an increase in the price of fertilizers.
Table 1.6.2 shows the trend in fertilizer prices from the year 2005-2008
Muriate of Potash (Granular)
Di-Ammonium Phosphate (Granular)
Source: Digest of Agricultural statistics 2008, Central Statistics office
1.8 Fertilizer distribution channels in Mauritius
The framework of the fertilizer sector differs from country to country. Gregory and Bumb (2006) have determined that by means of several IFDC market studies that there are six supply chain systems in sub-Saharan Africa (SSA) as shown in the figure. The list is not exhaustive as in some countries there may be only one type of system implemented whilst in some a combination of these systems work together. In Mauritius, a combination of 1, 2 and 5 exist presently to supply fertilizers to the local agricultural community.
Figure 1.8.1 Fertilizer distribution systems in Sub-Saharan countries
Wholesalers1. Domestic Production 2.Imported supply 3. Imported Integrated Supply.
Export Crop Processors
Procurement Agency4. Farmer Groups 5. Cooperatives 6.Government Agencies
Source: Gregory and Bumb 2006.
1.9 Main producers of fertilizers in Mauritius
The companies producing fertilizer for the local market are the Mauritius Chemical Fertilizer Industry (MCFI) and Island Fertilizers. The MCFI Company has been established in fertilizer production since 1975. It started its operation as a manufacturer and supplier of straight fertilizers to the local agricultural community. MCFI is also involved in export of fertilizers to countries in the region that is in the Indian Ocean and East African countries. Several grades of NPK fertilizers are manufactured for specific application as required by the local agricultural community. Table 1.9.1 shows the different fertilizer grades marketed by MCFI.The company also produces grades for export. The plant can also produce specific formulations of fertilizers based on the recommendation of the customer and include secondary nutrients and micro-nutrients such as Sulphur, Manganese, Boron, Iron and other elements.
Table 1.9.1 shows the different types of fertilizer marketed by MCFI.
18-0-27, 16-0-25, 21-0-21
17-8-25, 20-8-28, 23-8-23, 23-0-30, 28-0-24.
Vegetables, fruits and flowers
1.9.2 Stability of supply of fertilizers from 2003 to 2008.
The supply of fertilizers has not been stable during this time period as there were significant changes in raw materials in terms of price and specifications. There has also been a change in the consumption pattern of fertilizers and a decrease in the consumption volume. (Mr. R.Jatooa 2009, personal communication).
1.9.3 Problems currently faced by the fertilizer industry
The fertilizer industry is currently facing challenges in the form of unstable prices of raw materials which affect considerably the cost of production which is already high. There is also the problem of decreasing volume which is not economically feasible for bulk importation. This explains the high price of fertilizers. (Mr. R.Jatooa 2009, personal communication).
1.9 Definition of fertilizer
A fertilizer is defined as a compound which is added to the soil to provide the nutrients necessary for the proper growth and development of the plants. (Fertilizer manual 1998). From research it is known that 16 elements are essential for normal development of plants (Marschnner, 1995). Fertilizers can be classified as organic and inorganic fertilizers. Organic fertilizers are fertilizers that are made by living things. Examples of organic fertilizers are animal manures, compost, bone meal and blood meal. On the other hand, synthetic fertilizers are manufactured from non-living sources. An example is rock phosphate which supplies phosphorus.
It should be noted that organic fertilizers do not release the nutrients immediately upon application as before they can be utilized they have to be split into simpler forms for uptake by the plants. However since the nutrients are previously in organic form, they can be used directly by the plants. Organic fertilizers also amend the soil structure and increase the water and nutrient holding capacity of the soil.
Organic fertilizers have certain disadvantages as mentioned previously, they do not release the nutrients instantaneously. Nutrient deficiency may also arise from reliant use of organic fertilizers.
Inorganic fertilizers release nutrients more readily to plants upon application. However they have three main disadvantages namely:
The fertilizer can permeate in the soil thereby the nutrients are not available to the plants if the fertilizers is washed by rain or irrigation water.
Heavy use of chemical fertilizers can cause plant burns and can lead to dehydration as this is attributed to the presence of chemical salts in the composition of the chemical fertilizers.
The use of chemical fertilizers can lead in the long run to toxic concentrations and disturb the chemical equilibrium in the soil.
There are several elements that are required for the proper functioning of a plant.These are shown in table 1.6.1
Table 1.6.1: The essential elements, their form for uptake and functions in the plant.
Form for uptake
Functions in plant
Ions in solution ( HCO-3, NO-3,
NH+4 , SO42-) or gases in atmosphere (O2, SO2,N2)
Major constituents of organic substances
Ions in solution (PO43-, BO33-)
Energy transfer reactions and carbohydrate movements
Ions in solution
(K+, Mg2+,Ca 2+,Cl -)
Non-specific or specific components of organic compounds or maintaining ionic balance.
Cu, Fe, Mn , Mo , Zn
Ions or chelates in solution (Cu2+, Fe 2+, Mn 2+, MoO-, Zn2+
Enable electron transport and acts as catalysts for enzymes.
Source: From Mengel,K. and E.A, Kirby 1987. Principles of plant nutrition, 4th ed. International Potash Institute, Berne, Switzerland.
1.10 Fertilizer grade
The fertilizer grade is found on the fertilizer product which is denoted by a succession of 3 numbers. These numbers are spaced by 3 dashes. These numbers give an approximate value of each of the nutrients present in the fertilizer that is Nitrogen (N), Phosphorus (P) and Potassium (K). However it is important to note that the numbers represent only the amount of nutrients present in the fertilizer. These numbers are determined by standard analytical procedures. This grade excludes any nutrients present in the form which would not be available to the plants for uptake.(Fertilizer Manual 1998). Fertilizers also deliver secondary elements such as Calcium (Ca), Sulphur(S), Magnesium (Mg) and trace elements such as iron (Fe), Manganese (Mn), Molybdenum (Mo), Copper (Cu), Boron (B), Zinc (Zn). (Guide Agricole, AREU 2009)
1.10.1 Fertilizer grade
1.11 Types of fertilizers commonly used in Mauritius
There are basically two types of fertilizers that are most commonly used in Mauritius.
Simple fertilizer: It contains only one nutritive element (N or P or K e.g. Urea, Triple superphosphate)
Complex fertilizer that contain several nutritive elements (N, P and K), e.g. 13:13:20:2 which contains 13% N, 13% P2 O5 , 20% K2O and 2% MgO.( Guide Agricole 2004)
Table 1.11.1 shows the most commonly used nitrogen fertilizer grades in Mauritius.
Composition in the table is expressed as (%).
Calcium Ammonium Nitrate (C.A.N)
Source: AREU 2009.
Table 1.11.2 shows the most commonly used phosphate fertilizer grades
Monoammonium phosphate (MAP)
Diammonium phosphate (DAP)
Source: Guide Agricole, AREU 2009.
Table 1.11.3 shows the most commonly used blended fertilizer grades.
Source: Guide Agricole, AREU 2009.
1.12 Blended Fertilizers
Blended fertilizers were introduced in Mauritius because of the relatively high cost of complex fertilizers. Blended fertilizers can be produced in a wide variety of grades (%NPK). This is one reason that this type of fertilizers are very convenient to produce on recommendations by the agricultural community. Hence they are very popular throughout the world. Complex fertilizers are produced in factories by chemical reactions. Blended fertilizers on the other hand, are just mixed in bulk together so that there the overall size of the different fertilizer granules cannot be distinguished. The different fertilizer granules can thus be identified by their different colors. (Guide Agricole, AREU 2009)
In order to obtain the specific proportions that are required in the blends, a filler is used (inert material) which is combined together with the other granulated components. The filler material being insoluble does not dissolve upon contact with water and hence stays in the soil. This gives the impression that the blended fertilizer is not effective as compared to the complex fertilizers which is not the case. (Guide Agricole, AREU 2009).
1.13 Foliar Fertiliser
Leaves absorb nutrient in solution more effectively. Foliar fertilization is the process during which fertilizer solutions are sprayed directly on the leaves. In this type of fertilizer application, the main aim to supply the necessary nutrients in case of deficiencies in microelements such as Calcium, Iron, Boron, Copper, and Manganese. The nutrients in solution have the advantage in that they are immediately available and are assimilated by the plant.(Guide Agricole, AREU 2009).
1.14 Slow release Fertiliser
Slow-release fertilizers are fertilizers as the name suggests they release nutrients gradually in the soil water. In this type of fertilizer, the granules are protected with a layer, for e.g. urea coated with sulphur. Slow-release fertilizer has a significant advantage over standard fertilizers as the plants absorb the nutrients as they are released in small amounts by the granules. In this way, using these types of fertilizers reduces to a great extent the nutrient leaching to the environment. However slow-release fertilizers are quite expensive. (Guide Agricole, AREU 2009).
Table1.14.1 shows the roles of the major nutrients in plants.
Main element in proteins
Promotes growth, development of stem and leaves
Promote development of roots
Essential for growth of the plant
Plays an important role in fertilization
Controls important functions in the plant
Promote synthesis and accumulation of sugars.
Increase pest resistance.
Source:(Guide Agricole, AREU 2009).
A bio-fertilizer is either a liquid or a solid which contains microorganisms which can fix nitrogen from the air or make phosphate and potassium soluble in the soil. It is important to note that the fertility of the soil is greatly increased as this accelerates microbial activity. (Guide Agricole, AREU 2009).
Table 15.1 shows the distinct properties of some bio-fertilizers.
Improves fixation of Nitrogen in leguminous plants such as soja, peanuts, and cowpea.
Applicable specifically to leguminous plants
Improves fixation of Nitrogen
Applies to all types of plants
Improves rate of release of phosphate in the particles of soil.
Retrieves the potassium fixed in the particles of soil.
Mycorrhizae (Vesicular Arbuscular Mycorrizae) or VAM.
Improves the absorption of phosphate, water and micronutrients.
Source: Guide Agricole, AREU 2009.
16.0 Nitrogen fixation by Rhizobia
Nitrogen fixation by Rhizobia is very important in agriculture in many ways. Legumes such as peas, beans, lentils, soybeans, alfalfa and clover have a significant role to play in providing food for both meat-producing animals and humans. Higher yields are obtained in nodulated plants. They can grow well and achieve higher yields despite growing in soils where the structure is poor. They also provide fixed nitrogen for other types of plants. After harvest, the roots of legumes are left behind in the soil to decompose. This causes organic nitrogen compounds to be available for absorption by plants in the next crop cycle.
Farmers can derive benefits from this natural fertilization as there is less reliance on synthetic fertilizers. This can be done by rotating a leguminous crop with a non-leguminous one. Another advantage of planting legumes is that environmental issues such eutrophication of lakes and rivers are greatly reduced.
Rhizobium is a genus of bacteria that is a primary fixer of nitrogen in the soil. Their mode of action is by infecting the roots of leguminous plants which results in the formation of lumps or nodules. The nodules are actually the site where nitrogen fixation takes place. The enzymatic system of the bacteria provides a constant supply of reduced nitrogen to the host plant and the plant provides nutrients and energy to the bacterium. By this process, 90% of the legumes can become nodulated.
17.0 Vesicular Arbuscular Mycorrizae (VAM)
Mycorrizae is the interaction which exists between the fungus and the roots of a seed plant. This type of association exists extensively in nature (Harley 1983). They are present in every taxonomic group of plants. They will associate with any type of hosts as they lack host specificity. Mycorrizae also promotes the development of the soil environment. The role of Mycorrizae can be summarized as follows:
1. Mobilization of plant nutrients and water.
2. Greater of carbon stream flow in trees.
3. Association with other groups of microbes.
18.0 Soil Testing
It is commonly agreed that 17 chemicals are important for metabolism, growth, development and reproduction in higher plants. (Epstein, 1965, 1972; Brown et al., 1987; Marschner, 1995)
Soil testing is important so as to get an indication of the different nutrients available in the soil. It is necessary to improve the soil fertility status to avoid any deficiencies of any required elements in the soil. This will ensure an increase in crop yields. Soil testing comprises of the following components:
Samples of soil and plants to be prepared for analysis
Chemical extraction of samples
Determination of the concentration of nutrients in the extract.
Analysis of the nutrient concentrations so as to assess soil fertility
Derivation of corrective fertilizer applications.
(Dahnkez and Olson, 1990; Munson and Nelson, 1990; Peck and Soltanpour, 1990)
Soil analysis is defined as the chemical or physical tests which are carried out to determine concentration of nutrients in the samples. Soil and plant analysis data is the basis on which fertilizer recommendations can be made. This is a critical component in soil and plant testing programs
19.0 Soil Analysis
Schofield (1955) identified that there are two nutrient fractions in the soil: the quantity showing the amount of nutrients available in the soil and the intensity showing the strength of nutrient retention. The quantity shows the all the nutrients which are adsorbed in the soil constituents. The intensity shows the concentration of nutrients in the soil solution. The intensity and quantity are connected by the buffering capacity of the soil. The buffering capacity is a good index of the capacity of the soil to retain a specific amount of nutrients in solution. The quantity / intensity approach is valid only for nutrients like P and K (Holford, 1991; Holford and Doyle, 1992; Evangelou, Wang, and Philips, 1994; Raven and Hossner, 1994), but cannot be applied for nutrients that are mainly in organic forms or nutrients that are buffered by soil constituents.