TABLE OF CONTENTS ROLE AND IMPORTANCE OF AGRICULTURE IN THE CARIBBEAN Foreign exchange Contribution to GDP/GNP Food security Employment Environmental management CONSTRAINTS AFFECTING CARIBBEAN AGRICULTURE Climate Topography Appropriate Technology Rural Infrastructure Land Tenure and Fragmentation Credit Facilities Marketing Facilities Extension Services Praedial Larceny CLASSIFICATION OF CARIBBEAN FARMS Distinguishing Features of Farmers (According to Size) Large Farms Medium Sized Farms Small Farms Distinguishing Features of Farms (According to Produce) Crops Farm Livestock
Monoculture/Mono-cropping Mixed Cropping Mixed Farming Organic Farming Agro-Forestry Integrated Farm INSTITUTIONS WHICH SUPPORT LOCAL AND REGIONAL AGRICULTURAL Rural Agricultural Development Authority (RADA) Bodles Research Station: Jamaica Livestoc Association (J. L. A. ) Jamaica Agricultural Society (J. A. S. ): Scientific Research Council (SRC Sugar Industry Research Institute (SIRI) Caribbean Community Caribbean Development Bank (CDB) Caribbean Agricultural Research and Development Institute (CARDI ) Caribbean Food and Nutrition Institute (CFNI) University of the West Indies (UWI)
College of Agriculture, Science and Education (CASE) Inter-American Institute for Cooperation in Agriculture (IICA) Food and Agriculture Organization (F AO) Organization of American States (OAS) Inter-American Development Bank (I. D. B. ) The Canadian International Development Agency (CIDA) Caribbean Basin Initiative (C. B. I) United States Agency for International Development (USAID) European Union (EU) INTRODUCTION TO SOIL SCIENCE Functions of Soil in our Environment Soil Formation Weathering Soil formation factors Soil Profile Physical Properties of soils Soil texture Soil Structure
Porosity BULK DENSITY SOIL COLOUR SOIL WATER Importance of soil Organic Matter Chemical Properties of the soil Soil pH Plant nutrients HOW THE SOIL HOLD PLANT NUTRIENTS? MANAGING SOIL FERTILITY FERTILIZERS Advantages of organic fertilizers Disadvantages of organic fertilizers Inorganic fertilizers Fertilizer grade Advantages of inorganic fertilizers Disadvantages of inorganic fertilizers Practical activity Identifying types of fertilizers Methods of applying fertilizer Importance of plant sexual reproduction in agriculture The flower Pollination Types of pollinations Self pollination Cross pollination
Fertilizatio ROLE AND IMPORTANCE OF AGRICULTURE IN THE CARIBBEAN Foreign exchange The agriculture sector earns foreign exchange by exporting traditional and non-traditional products. In addition to earning foreign exchange, the agriculture sector may also produce food and raw material for local consumption; this reduces the need to import similar products, resulting in the saving of foreign exchange. The foreign exchange earned and saved is used to purchase other goods and services which the country needs/want but does not produce. Imported products must be purchased using foreign exchange.
In addition to trading, foreign exchange is also used to repay international debt. Contribution to GDP/GNP GROSS DOMESTIC PRODUCT – GDP GROSS NATIONAL PRODUCT – GNP GDP and GNP are means of measuring the national income of a country. The GDP measures the value of goods and services produced locally, in a given period. The GNP is determined by adding the value of goods and services produced in a country (GDP) and also what is earned abroad and returned to the country, in a given period. GDP = AGRICULTURE + TOURISM + MINING + MANUFACTURING etc. GNP = AGRICULTURE + TOURISM + MINING + MANUFACTURING etc. + EARNINGS FROM ABROAD
Agriculture contributes to the overall wealth of a country by contributing to GNP and GDP. As the contribution from agriculture and other sectors increases the wealthier the country becomes. This means more funding will be available to improve infrastructure and services such as roads, education and health. The Jamaican agriculture sector contributes about seven percent to GDP, only tourism contributes more. Food security Food security is concerned with the availability of adequate supply of food and access to the food by all the citizens of a country. Food security exists when all people at all times have physical and economic access to ufficient, safe and nutritious food to meet their dietary needs and food preferences. Food security can be affected by; • Availability or access to arable lands for agriculture • Technology used • Climatic conditions • Conflicts • Ability to import food • Poverty FOOD SECURITY = ADEQUATE FOOD SUPPLY + ACCESS TO FOOD BY ALL Employment Agriculture is a major source of employment in the rural areas of most Caribbean countries. Therefore, agriculture is the primary means of promoting rural development and reducing rural to urban migration and its consequence urban decay.
Employment in agriculture ranges from unskilled workers to highly trained professionals such as an agronomist or an agricultural engineer. Also, agriculture offers direct employment for example a broiler farm [pic] or an extension officer. There is also indirect employment in down streams. Down streams industries, such as food processing, generally use agricultural products as raw materials to produce value added products or manufacture new products. Supermarkets, financial institutions and businesses benefit from the earnings of individuals involved in agriculture.
Environmental management Through agricultural activities man interacts with the environment. The effects of this interaction may be positive or negative. Since agriculture depends on the natural resources, the goal of all persons who benefit directly and in directly from agriculture should be to promote the use of agricultural practices that are environmentally friendly. CONSTRAINTS AFFECTING CARIBBEAN AGRICULTURE Climate The major areas of consideration are: temperature and rainfall. The climate of the Caribbean is the tropical marine climate; therefore it is warm and moist.
The combination of warmth and moisture create ideal conditions for many pests and diseases that affect both crops and livestock. Also, the high temperatures make it more difficult to successfully rear some breeds of livestock in the Caribbean, especially those which originate in temperate areas such as Europe. Topography Topography refers to the relief or the shape of the land. The topography of most Caribbean islands is hilly in the interior with most of the flat land near the coast. The limited flat land is generally used for housing and settlements, manufacturing industries and plantation type agriculture e. g. sugar cane.
Steep slopes affect farming by: • Limiting access to farm plots • Restrict the use of farm machines • Increase the risk of soil erosion Appropriate Technology Technology: the use of tools, machinery and knowledge and to complete tasks. Increasing production in agriculture is linked to the use of modern technology e. g. tractors, hybrid seeds, and efficient irrigation systems. Appropriate technology refers to the use of tools, machinery and knowledge which is suited for local conditions or a specific area or condition. Technology should be appropriate to the economic status of the farmer, farm size, climate and level of education etc.
Appropriateness technology for small farmers can be judged using the characteristics shown below; • Simple • Low maintenance • Locally made • Access to spare parts • Easy to operate • Affordable • Small/compact [pic] [pic] Rural Infrastructure The farm family needs to have access to basic amenities for both agricultural and domestic activities. If rural areas are not provided with some of the basic infrastructural needs, farmers will not be very productive; also the business of farming may become less attractive or no longer feasible to the farm family. Some of the basic infrastructure includes: • Electricity Water supply • Proper roads • Telephone • Health care • Schools Land Tenure and Fragmentation Land tenure speaks to the ownership of land. Most small farmers do not own their own land or own very small fragmented plots usually in hilly areas. When farmers do not own their own land, they are not motivated to develop the land or put permanent structures on the land. Land fragmentation occurs as land is divided among family members from generation to generation. The land is divided into numerous plots and not all the plots are generally used for agricultural production but for other purposed such as housing.
Credit Facilities As with other types of businesses it is often very necessary to borrow money from lending institutions to start, expand or acquire assts for an agricultural enterprise. Because farming is considered to be a high risk business, institutions are not very willing to lend money for agriculture. Very often farmers complain that the cost of borrowing money (interest rate) is too high; while the price of the products they produce is relatively low. Some farmers will experience difficulty accessing loans because they lack suitable collateral such as land.
Collateral is material of value used to cover the cost of the loan in the even that the borrower is unable to pay. Marketing Facilities Marketing involves bringing the producer and the consumer together. Marketing also includes transporting, pricing, packaging, storage and advertising. Farmers in Jamaica experience difficulty in selling their produce due to: • A lack of properly organized systems to bring buyers and sellers together i. e. buyers are not aware of what farmers are producing and farmers are not fully aware of the needs of buyers. • Competition from imported agricultural products
Extension Services Although there is an increasing number of professionals now operating farming enterprises, most Jamaican farmers are relatively old and have only basic education (grade 9). Therefore there is need to give these farmers constant and individual help to improve their agricultural knowledge. Extension officers provide a vital link between the farmer and the researcher that develop modern farming technology and solutions for on the farm problems. The economic constraints being experienced in Jamaica have resulted in the reduction in the size of the extension service.
Praedial Larceny Nothing is more discouraging to a farmer than the theft of his produce. CLASSIFICATION OF CARIBBEAN FARMS Farms are classified according to size and what they produce. Distinguishing Features of Farmers (According to Size) Large Farms Large farms occupy more than 25 hectares, mainly produce one crop or type of livestock and are geared for export. These farms are operated and managed by individuals, co- operations or government and in some cases absentee owners. They employ a skilled labour force as well as semi-skilled and unskilled workers.
They farms tend to be highly mechanized or in some cases little mechanization is used but instead large numbers of workers. The profits from these farms in the case of foreign owners are repatriated. Medium Sized Farms The size of these farms range anywhere from 2. 5 to 25 hectares. They are owned and operated by the farmer and usually requires hired labour. These farms usually produce a variety of crops or livestock or both crops and livestock for domestic use. In recent time medium sized farms are accessing export markets. Small Farms These farms are less than 0. 5 hectares to a maximum of 2. hectares. They are owned and operated by the farmer and family labour is used. They produce for local markets and use simple hand tools e. g. hoe, fork, and cutlass. Distinguishing Features of Farms (According to Produce) Crops Farm These farms are of all sizes and produce a variety of crops for the local and possibly export market. Some mechanization is involved especially in land preparation and pest and disease control. The farmer usually owns the land and some labour is hired. [pic] Livestock These farms are also of all sizes depending on the type of enterprise e. . fish, cattle, rabbits and goats. It is owned and operated by an individual, group or government and production is mainly for the domestic market e. g. pork, beef, fish are all used in Jamaica. Monoculture/Mono-cropping In a mono-cropping system, the farmer concentrates on growing only one major crop e. g. sugarcane on a plot of land or in a particular area for an extended period of time. Relatively few of these farms are found in the region. Absentee owners appoint managers to run the farms. In general, these farms are productive but the profits are exported.
In cases where the farms are locally owned the profits remain in the country and help with its development. On these farms soil and crop management are uniform, since they are dealing with one crop. This repeating of crop and soil management practices can have negative effects such as: • Grater opportunity of spreading pests and diseases, which may destroy the entire crop. • Continuous ploughing with heavy equipment can destroy soil structure • Cultural practices such as burning of sugar cane can destroy soil structure and beneficial soil organisms. Mixed Cropping
In mixed cropping the farmer depends on several plots for his income. Maximum use is made of land space and it is easier to check the spread of pest and diseases. In mixed cropping: • Crops may be grown on the same farm but on different plots. [pic] • Crops may be intercropped on the same plot. [pic] Situation: a farmer often grows one main crop e. g. sugar cane but also cultivates other (cash crops), which he uses to provide his weekly supply of food and to help pay his bills by selling the surplus produce. Such a situation is considered mixed cropping since he has other crops on which he can depend. Mixed Farming
Involves the growing of crops and the rearing of animals on the same farm. They can be of and size but usually medium to large and production is basically for a local market, some produce may be exported. The farms are owned and operated by individuals, groups or government. Advantages: o Maximum use is made of land space. o Farms have more than one source of income. o It is easier to check the spread of pests and diseases. Disadvantages • A higher level of management is required. • There is a need to find market for different types of produce. • Animals can damage crops if the y are not properly enclosed or tied.
Organic Farming Organic farming is the use of agricultural systems to produce food and fiber without the use of artificial pesticides, fertilizer and genetically modified plants. Crop rotation and the building of biodiversity are very important. Pesticides used come from plants and are used as a last resort and their effects are short lived. Soil amendments come from renewable resources such as farmyard manure and composts. The strategy is to build up healthy soils through cover crops, composts and organically based amendments to build up healthy soils. These plants are better able to resist pest and diseases.
Weeds are controlled through cover crops, mulching, flame weeding and crop rotation. When pests and diseases get out of control a variety of strategies are used for their control e. g. insect predators, mating disruption, traps, barriers and bio-chemicals. Agro-Forestry Agro-forestry is an integrated land use system. It refers to land –use systems in which trees are grown on the same land as agricultural crops and/or animals in a spatial arrangement or in a time sequence. Some examples are coconuts under-planted with pasture, apiculture with tree systems and aquaculture under mangroves.
Agro-forestry systems resemble the natural ecosystems. The general aim of agro-forestry is to supply and increase a sustainable output of the basic necessities including cash. Agro-forestry is important because the following reasons. • Environmental deterioration – due to the actions of man, natural disasters and volcanic action lead to deforestation. • High rates of oxidation of organic matter due to high temperatures as well as excessive evaporation of moisture. • Soil erosion. • Population pressure for land for a variety of purposes such as housing. • Need for fuel wood. Integrated Farm
Farms are said to be integrated when the waste products from one enterprise is used as an in put in another production enterprise e. g. poultry waste can be used in fish farming and cattle rearing. Integrated farms attempt to eliminate the accumulation of agricultural waste by further utilization in production. Sugarcane Feed for ruminants (cattle) Waste Garden (compost) Garden excess and waste Feed ruminants INSTITUTIONS WHICH SUPPORT LOCAL AND REGIONAL AGRICULTURAL For a country’s agricultural sector to maximize its potential and contribute to a nation’s development; numerous organizations and institutions must play an integral role.
These institutions may be government or private, local based, regional or international. The roles played by these institutions may encompass: Education ? Research ? Technical assistance ? Poverty reduction ? Rural development These organizations may form a cornerstone for development and ensure sustainable development, food security, poverty reduction, and prosperity. Some institutions have specific roles e. g. CFNI – nutrition. While some are broad based dealing with a wide cross section of development e. g. CDB. Rural Agricultural Development Authority (RADA)
The objectives of RADA include: ? To provide technical extension assistance primarily to farmers in rural Jamaica in an effort to increase production and productivity. ? To train and develop extension personnel at all levels through in-service training programmes, geared towards improving their efficiency. ? To administer farmer training programmes and workshops thereby rendering farmers more knowledgeable and capable. ? To catalyze agricultural credit and input for small farmers. ? To aid in organization of marketing chains beneficial to both farmers and consumers. To cooperate with agencies involved in the development of rural infrastructure with a view to improving the quality of life in rural communities. ? To develop and operate service centres at strategic locations around the island thus bringing the service closer to farmers. ? To be the implementing agency for selected projects that impact on farmers and the biological environment. E. g. watershed development projects and farmer registration. ? To provide a free flow of information from policy makers and research organizations to farmers and from farmers upwards to these same persons.
Bodles Research Station: Government funded research institution that carries out research in both crop production and animal husbandry to develop new and improved methods of farming, pest and disease control. They also seek to develop new plant and animal breeds which are suitable for local conditions. Jamaica Livestock Association (J. L. A. ): The J. L. A. is concerned with the development of the Jamaica livestock sector. It is a public company offering shares therefore it is concerned with the welfare of share holders.
They provide agricultural support services for improving development of the industry such as quality input and technology development and implementation. Jamaica Agricultural Society (J. A. S. ): The JAS represent the interests of all farmers lobbying for agricultural friendly policies for agricultural sustainability and development. They also promote and support agricultural and industrial shows as well as operating a supply subsidiary (JLA farm stores), providing agricultural inputs at affordable costs to farmers. Scientific Research Council (SRC): They undertake research into new and improved technologies in agriculture.
They are currently spearheading efforts to implement tissue culture and hydroponics in Jamaica. Sugar Industry Research Institute (SIRI) SIRI main function is to research and develop methods to improve agriculture technology as it relates to sugar cane production. They aim to improve efficiency in all areas of sugar cane production. Their main functions are: • The development of new varieties of sugar cane which are high yielding, drought resistant, pest and disease resistant. • The development of machinery and equipment suitable for Jamaican conditions. • Provide technical assistance in irrigation, drainage and water management. Develop ideal fertilizer preparations based on the nutritional requirement of a crop. • Promote the safe and efficient use of agro chemicals e. g. herbicides and insecticides. • To study, monitor and provide technical advice in control and eradication of pests and diseases. CARICOM – Caribbean Community (Established by the treaty of Chaguarnas May 1, 1973) Aim is to enhance regional trade, develop common policies, and act as a negotiating body among member states. So as to promote economic, social, cultural and political development through integration. Caribbean Development Bank (CDB)
Provides loans for development and establishment of agricultural industries and farms e. g. irrigation, training, fisheries, as well as infrastructural development e. g. roads, water supply. Caribbean Agricultural Research and Development Institute (CARDI ) • Provide for and conduct research into farming methods, pest and disease control, plant and animal breeding, technology for long term development. • Coordinate and integrate research efforts in member states. • Undertake training of farmers and agricultural personnel. • Improve the utilization of modern technology to boost agricultural production.
Caribbean Food and Nutrition Institute (CFNI) • Offers technical support for reducing malnutrition • Promote proper nutrition education and provide educational material to this end. • Develop nutrition policies • To collaborate with governments to improve food security. • To improve nutritional aspects of health services. University of the West Indies (UWI) • Provide degree training in agriculture and related fields • Conduct agricultural research for improving farming methods and pest and disease control. College of Agriculture, Science and Education (CASE) Offers training in agriculture.
Inter-American Institute for Cooperation in Agriculture (IICA) A specialized agency of the O. A. S. their aim is to promote agricultural development in a sustainable manner working with governments and Ministries of Agriculture. Their focus is geared toward • Rural development and well-being. • Diversification of agricultural production. • Value-added production (agro-processing). • Improving the region’s position in international trade. • Research and development Food and Agriculture Organization (F AO) An organized branch of the United Nations which aims to • Promote agricultural development. Pursue food security and improve nutrition. • Develop infrastructure in rural areas. • Provide information and technical assistance on a project basis to farmers. • Provide a neutral platform for countries to meet and discuss issues and advice them on policy making. • Coordinate government efforts at food security and improved nutrition. Organization of American States (OAS) Includes Thirty four (34) member states from the Americas. Provides technical assistance to countries and aims to improve health care and public administration. Inter-American Development Bank (I. D. B. )
The oldest and largest regional institution of multilateral development. The aim is to accelerate economic and social development in Latin American and Caribbean countries. Operations cover the entire spectrum of infrastructure, energy, transportation and urban development. Current lending priorities: poverty reduction, social equity and modernization. The Canadian International Development Agency (CIDA) The lead organization in delivering Canada’s official development assistance programme. Assistance is provided in the form of goods and services, transfer of knowledge, skills and financial contributions.
Areas of concentration include: – basic human needs – infrastructure – private sector development – women in development – human rights – environmental protection. These objectives are achieved by working with both the private sectors and governments of respective countries. Caribbean Basin Initiative (C. B. I) Enacted as Caribbean Basin Economic Recovery Act by United States. Products from beneficiary countries may be eligible for duty-free treatment in the U. S. A. United States Agency for International Development (USAID) Undertakes numerous projects aimed at improving the quality of life of citizens in developing countries.
They also aim to expand democracy and free market activities ultimately leading to economic growth. European Union (EU) The EU provides grants and loans for a wide range of development projects and environmental protection initiatives in developing countries. They also provide technical assistance for many of these projects. INTRODUCTION TO SOIL SCIENCE Functions of Soil in our Environment. ? Habitat for organisms; Microbes, earth worms, rodents ? Medium for plant growth; Provide essential minerals and water. ? Important component in the water cycle ; storages in pores and evaporation ?
Engineering medium; construction of roads and building etc. Soil Formation Soil Composition [pic] Soil formation is slow process. In the best conditions 1mm of soil may be form in a year. However, under poor condition it may take thousands of years for the same quantity of soil to form. Although soil is a renewable resource, in many areas soil is being lost at a much faster rate than it can be produced. SUMMARY OF SOIL FORMATION PROCESSES [pic]Transformation – weathering and decomposition [pic]Translocation – movement of soil materials up or down the soil profile [pic]Addition – rainfall, OM, deposited rock materials pic]Losses – erosion, washing out of soil material in the ground water(leaching) Weathering This is the physical and chemical breakdown of rocks and the mineral found in rocks. i) Physical weathering or disintegration involves the break up rocks into smaller fragments. Physical weathering is often referred to as mechanical weathering, since it involve the action of forces. Agents of physical weathering or disintegration: ? Temperature changes: – Contraction and expansion weaken the structure of the rocks. ? Running water ? Plants: – the roots of plants can grow between rock spaces and break up the rocks as they grow and become larger. Humans and animals The diagram shows the result of physical weathering; a single rock disintegrated into many fragments [pic] ii) Chemical weathering involve changing the chemical composition of rock s/ the minerals in rock via chemical reactions. Primary minerals such as quartz Sio2 are changed into changed into secondary mineral such as aluminium silicates (clay mineral). Chemical weathering is accelerated by the physical disintegration of rocks, which increases the surface of rocks, causing the rate of chemical reactions to increase.
In addition, water and warmth are important factors which, influencing the rate of chemical weathering. Water is a universal solvent in which reactions can take place while, as temperature increases the rate of reactions increases. EXAMPLES OF CHEMICAL WEATHERING Carbonation and solution: Water combines with Carbon dioxide to form carbonic acid. Examples: (1) H2O + CO2 ———— H2CO3 + CaCO3 ———Ca(HCO3)2 (2) CaCo3 + H2CO3 ——- Ca2+ + 2HCO3- Hydration: – Water combine with rock minerals causing a chemical change in the mineral structure.
Examples: anhydride (CaSO4) + Water (H2O) = Gypsum (CaSO4-H2O) 2Fe2O3 + 3H2O ——- 2Fe2O3. 3H2O Hematite limonite Hydrolysis: The water molecule splits in to H+ and OH-and reacts with minerals CaSiO 3 + 2H2O ——– HSiO3 + Ca(OH)2 Calcium silicates silicic acid calcium hydroxide Oxidation: Oxygen combines with mineral elements to form oxides. Example: a rusting sign post. Soil formation factors These are environmental factors, which determines the type of soils that are formed i. soil colour, profile depth, chemical features and biotic characteristics. i) Parent material: Parent material refers to the type of rock material from which soil forms. It includes bedrock, transported (by water, wind or gravity) and deposited materials originated from rocks. Alluvial – transported by water Colluvial – dislodged and deposited by gravity *** Soil is not necessarily formed from the underlining bed rock *** The parent material contributes to the physical and chemical properties of the soil, such as texture, pH, mineral content. |ROCKS CHRACTERISTICS | | | | |Igneous rocks |Rocks formed from cooled molten material | | |Volcanic rocks may acid or basic | | |Granite is an example of igneous rocks | | | | |Sedimentary rocks |The most abundant rock types | | |Formed from deposited materials included rock fragments | | |Usually layered | | |Limestone and sand stone are examples | | | | |Metamorphic rocks |Formed from sedimentary rock when these rocks are exposed to great heat and | | |pressure. | | |Example limestone changed to marble | PARENT MATERIAL |SOIL PROPERTIES | | | | |SOFT LIMESTONE |DARK IN CLOUR | | |SHALLOW | | |UNDERLAID WITH MARL | | | | |HARD LIMESTONE |SOIL VARY IN COLOUR FROM BROWN TO RED, INCLUDING BAUXITIC SOILS | | | | |SHALES |FREE DRAIINING | | RICH IN POTASH | | |PRONE TO SLIPPING AND EROSION | | | | |PURPLE CONGLOMORATES |OCCUR MAINLY ON SLOPES | | |SUSCEPTABLE TO EROSION | | |LOW WATER HOLDING CAPACITY | | | | |OTHER CONGLOMORATES |ACID CLAYS | | |LOW FERTLITY | | | | |GRANITE AND POPHYRY |GRAVELLY SOIL | | |SHALLOW | | |ACIDIC | | |LIGHT TEXTURE | | |EASELY ERODED | ii) Climate: Agents of climate such as temperature, moisture (rainfall) and wind contributes to rock disintegration and chemical weathering and consequently the type soil that is formed. Warm temperature, as is the case in the tropics, increase the rate of weathering. The amount of moisture present will also affect the rate of soil formation, by influencing the rate of weathering and decomposition. iii) Topography: the topography is the shape or contour of the land surface.
Soils formed on slopes then to be thinner than those that are formed on gently sloping lands. Low lying areas, which are poorly drained, have different chemical properties indicated by a grey colour down the soil profile. [pic] iv) Time: the longer the soil formation processes are in action the soil horizons would be more developed and also the soil would be more weathered. v) Biotic factors (vegetation and animals): Soil animals such as earthworms influence soil development by mixing soil components and aerate soils as they burrow through the soil. The mixing action enhances the rate of chemical and physical change in the soil. Fungi and bacteria decompose organic matter.
The leaves and roots of plants add organic matter to the soil and contribute to the weathering of rocks. Soil Profile The soil profile is a vertical section of view of a soil showing the horizons or layer. [pic] Soil Profile OSuperficial surface layer consist mainly of plant remains such as fallen and other partially decomposed organic materials ATop soil – divided into two layers on the basis of soil colour ? The upper layer is darker due to a higher concentration of organic matter ? Usually there is an abundance of soil organisms and plant roots ? The top soil generally has a loose structure ? Usually the most fertile layer E
BSubsoil- colour of this layer is red to orange due to the accumulation of mineral called oxides ? Proportion of gravel may begin to increase ? Clay content increases caused by the downward washing and accumulation of clay. ? The tap roots of some plants may be visible ? The soil is more compact CWeathered rock/Parent material – contain gravel or generally coarse material D/RBed Rock – Solid rock or parent materials Importance understanding the Soil Profile • Soil horizons help to determine the soil type. • Most plant nutrients are present in the top soil, which can be used to determine the soil fertility. • Subsoil compactness will give a hint to the drainage of the soil. Type of bedrock and parent material will influence chemical and physical soil properties. Physical Properties of soils Soil texture The texture of a soil is determined by the ratio of sand, silt and clay particles present in the soil. The percentage of sand, silt and clay soils can be used to classify soils into three main texture classes; [pic]Sandy soils —— Coarse [pic]Loamy soil —— Moderately coarse, medium to moderately fine • Clay Soils ——- Fine NOTE – IN THE FIELD THERE ARE MANY VARATION TO THESE TEXTURE CLASSES. THE SOIL TEXTURE TRIANGLE BELOW SHOWS THE MAJOR SOIL TYPES. [pic] In the field soil texture can be determined by the feel method i. e. feeling the soil between the finger.
Hence, soil texture can be simply defined as the feel of the soil between the fingers. Soil texture is very difficult to change in the field but on a small scale adding enough of another soil type and mixing thoroughly can modify the texture of one soil type. Soil Particles and size Gravel200 – 20 mm Fine gravel20 – 2 mm Coarsesand2 – 0. 2 mm Fine sand0. 2 – 0. 02 mm Silt0. 02 – 0. 002 mm Clayless than 0. 002 PROPERTIES OF SOIL S AND SOIL PARTICLES Clay ? Clay Particles stick together ? Particles are closely packed ? Highest percentage of micro pores ? Low porosity ? Good for fish ponds and growing rice ? High water holding capacity ? Moderated to high CEC ? Low drainage ? Moderate to high shrinkage and swelling Easily compacted ? Resist wind erosion ? Resist change in soil pH ? Retards leaching ? Rich in nutrients ? Poor structure ? Have negative electric charge (to attract Positively charged nutrients) Sand ? Particles do not stick together ? Particles can be seen with the naked eye. ? Particles loosely arranged ? Large pore spaces ? Resist compaction ? Easily tilled soon after wetting ? OM decomposed rapidly ? Generally coarse ? Well aerated ? Well drained ? pH is easily changed ? Poor water holding ability ? High rate of leaching ? Low nutrient content Silt ? Particles are smooth and powdery ? Intermediate between clay and sand ?
Particles feel smooth but not sticky ? Have and electric charge ? Easily compacted ? Easily blown by wind erosion LOAMS Soils classified as loams tend to demonstrate the properties of the three particles in an almost equal proportion. In the field, there are different types of loams e. g. clay loam, silty clay loam, sandy clay loam and sandy loam. Identifying Texture by Feel Feel test – Rub some moist soil between your fingers. • Sand feels gritty. • Silt feels smooth. • Clays feel sticky. Ball squeeze test – Squeeze a moistened ball of soil in your hand. • Coarse textures (sand or sandy loam) soils break with slight pressure. Sandy loams and silt loams stay together but change shape easily. • Fine textured (clayey or clayey loam) soils resist breaking. Ribbon test – Squeeze a moistened ball of soil out between your thumb and fingers. • Sandy soils will not ribbon. • Loam, silt, silty clay loam or clay loam soil ribbons less than 1 inch. • Sandy clay loam, silty clay loam or clay loam ribbons 1 to 2 inches. • Sandy clay, silty clay, or clay soil ribbons more than 2 inches. A soil with as low as 20 percent clay, may behave as a heavy clayey soil. A soil needs 45 percent to over 60 percent sand to behave as a sandy soil. [pic] Activity ; Determine the texture of soil samples Soil characteristics |CLAY SOILS |SANDY SOILS |LOAMS | |Soil Conditions when dry | | | | |Do not from stable aggregates | |^ | | |Easily broken | |^ |^ | |Moderately easily broken | | |^ | |Hard and stable |^ | | | | | | | | |Soil conditions when wet | | | | |Very stable aggregates |^ | | | |Moderately stable | | |^ | |Very unstable aggregates | |^ | | | | | | | |Ability to form ribbons | | | | |Do not form ribbons | |^ | | |broken appearance of ribbons | | |^ | |Thin ribbons, will brake | |^ | |Very long & flexible ribbons |^ | | | Soil Structure Soil structure describes the arrangement of individual soil particle. Individual soil particles come together to form aggregates, which may appear, in a number of shapes; [pic]Granular and crumb – aggregates are loosely arranged, usually found at the soil surface especially those having high organic matter content, it is considered to be the ideal structure soil structure. [pic] [pic]Plate like – generally found in the subsoil can be produced by soil compaction; this type of structure may reduce air, water movement and also hinder the penetration of roots. [pic] Blocky – this type of structure is usually seen in the Subsoil – associated with clay soils [pic] [pic]Prism like or columnar – found in the subsoil of clays [pic] [pic]Structure less soil has single grains or massive structures. [pic] ACTIVITY: Use a pitch fork to remove small sections of top soil and subsoil, identify the types of soil structure observed. Porosity Pores are spaces occurring naturally between soil particle and soil aggregates and directly depends on the soil structure. Porosity measures the amount of pore spaces in a soil sample. Pore spaces are important for the growth of plant roots and the movement of soil water and air. Based on size there are two types of pores observed in soils macro-pores and micro-pores.
Macro-pores allow water and air to move through the soil at a faster rate, while micro-pores holds water more tightly therefore they act as long term storage of water. [pic] | | | |Pore spaces |Features | | | | |Low Porosity |Water logging, inadequate oxygen in the soil, hinder root penetration, micro-pores | | |dominates. | | | |Improve porosity |Add organic matter (compost) | | | | |Reduce porosity |Soil compaction | WHAT IS SOIL BULK DENSITY? This is the mass per unit volume of a dry soil sample. The volume includes the soil particles and pores spaces. Soils that are more compact usually have a higher bulk density that is having more soil particles and less pore spaces. REMINDERS Low porosity = higher bulk density
Compact soils = low porosity = high bulk density* Clay soil = generally low porosity Sandy soils = higher porosity [pic] Activity: list the characteristics of soil with poor soil structure | | |How does soil structure influence plant growth? | SOIL COLOUR The colour of the soil gives clues to the physical and chemical properties of the soil. The soils can be used make a quick evaluation of soils in the field. Soils colours are mainly determine by oxides of metals and organic matter. Soils display a wide range colour for example; • Reds • Browns • Yellows • Black • Green • White
Organic matter cause soils to be darker in colour, which may also hide the effect of oxides. Organic matter is associated with good soil structure as well as soil fertility. Iron oxides tend to produce soils that are yellow, brown or red. The colour will depend on the form iron oxide. Carbonates such as Calcite (CaCo3) give soils whitish colour. • Bright soil colours are associated with well-drained soils and well aerated soils • Grays and mixture bright colours and grays (mottled) indicates a poorly drained and poorly aerated soils • When soil that are rich in iron oxides becomes water logged the iron is reduced form the ferrous to the ferric from which give the soil a grey colour |Condition | | |Subsurface soil colour | |Soils in anaerobic conditions, such as those in poorly | | |drained depressions, will normally have dull, grey |Water-logged soils, poor aeration | |B-horizons. Alternatively, aerobic soils on well-drained and |Dull grey (if in low rainfall soils 0-20 in) | |aerated slopes have bright reddish-brownish colours. | | |Well drained soils | | |Yellow, red-brown, black (if in forest soils) | | | | | |Poorly drained soils | | |Mottled grey (if in humid soils) | | | | SOIL WATER Water is essential for plant growth. Soil is capable of being a storehouse of water and becoming the main source of water for land plants.
Soil water plays a significant role in several natural processes- evaporation, infiltration and drainage of water, diffusion of gases, conduction of heat, and movement of salts and nutrients are all dependent upon the amount of water present in soil. Plants meet their water requirement from water stored in soil. Soil moisture can be improved with aeration. Soil water is contained in soil pores Soil water contains dissolved substances for example nutrient elements and organic matter HOW DOES WATER MOVE UPWARD IN THE SOIL? Think about narrow tubes of different diameter placed vertically in beaker with water, as the diameter of the container decreases the height of the water in the tubes increases.
The forces involved are called cohesion and adhesion. ? Cohesion attraction between water molecules ? Adhesion attraction between water and soil surface CLASSIFICATION OF SOIL WATER ? FIELD CAPACITY – water held in the soil after excess water has drained away ? CAPILARY WATER – water held by cohesion and adhesion [surface tension] ? GRAVITATIONAL WATER – water that drains under the influence of gravity especially after rain fall ? HYGROSCOPIC WATER – water that is held tightly around soil particles. This water is nit available to plants. Importance of soil Organic Matter ORGANIC MATTER (OM) = Decaying and decayed plant and animal remains • Low percentage present in soil Colloidal in nature • Have electric charge. • Binds mineral particles to form stable aggregates. (improve soil structure) • Humus is the final stage of decomposed material • Responsible for the loose nature of productive soils. • Increase water-holding capacity. • Source of plant nutrients such as phosphorus and sulphur and major source of nitrogen. • Supply food for soil organism. Chemical Properties of the soil Soil pH The term soil pH refers to the degree of acidity or alkalinity of a particular soil type. The soil pH or soil reaction is determined by the concentration of Hydrogen H+ and hydroxyl OH- in the soil. ? H+ higher than OH- soil acidic OH- higher than H+ soil alkaline soil In addition alkaline soils have more Ca, mg, K, and Na ions (base forming ions), while acid soil have more acid forming elements such as aluminium ions. ___________ Items & pH ________ Most acid soils 4. 0-6. 0 Lemon juice 2. 2-2. 4 Orange juice 3. 4-4. 0 Vinegar 4. 0-4. 5 Acid rain 3. 0-5. 0 Clean rain water 5. 5-5. 7 Fresh milk 6. 3-6. 6 Blood plasma 7. 0-7. 2 Mild soap solution 8. 5-10. 0 ____________________
The pH scale ranges from one to fourteen; a pH of 7 is neutral, above 7 acidity increases while below the neutral point alkalinity. | | |ACIDITY INCREASING | | |ALKALINITY | | | | | | | | |INCREASING | | | |1 |2 | |Nitrogen |Essential component of chlorophyll, promote growth especially leaves. | |Phosphorus |Important role in fruit and grain maturity, stimulates flowering, promote the development of | | |the root system. |Potassium |Carbohydrate formation and translocation, essential for the development of flowers, fruits | | |and seeds. | |Calcium |Occurs in the cell walls | |Sulphur |Formation of amino acid which forms protein | |Magnesium |Present in chlorophyll | |Micronutrients | | |Iron | |Sodium | | |Chlorine | | |Selenium | | |Manganese | | |Zinc | | |Copper | | |Molybdenum | | |Boron | | HOW THE SOIL HOLD PLANT NUTRIENTS? Cation exchange capacity (CEC) explains how the soil is able to hold cations such as Ca2+, Mg2+, K+, H+ and NH4+, which are in important for crop nutrition. Clay and humus both have a net negative charge, so they give the soil the ability to attract cations. These ions will become attached to the soil complex (see diagram below). The CEC cation exchange value can be used in evaluating soil fertility. Soils with higher CEC are usually more fertile for example soil with high clay and or organic matter content.
Anion such as sulphates, nitrates and phosphates are not attach to the soil particles therefore they are easily leached from the soil. HOW DOES CEC AFFECTS ABILITY OF THE SOIL TO BUFFER AGAINST pH CHANGES? [pic] MANAGING SOIL FERTILITY The soil is a very import resource in crop production. Therefore, it must be managed properly to ensure the best crop yield possible on a continuous basis. It is very important that we understand how the physical and chemical soil properties affect the fertility of soils FERTILIZERS Fertilizers are materials organic and inorganic which supply elements essential for the growth of plants Organic fertilizers Organic fertilizers are materials from animal waste and plant material which are used to supply plant nutrients.
Examples of organic fertilizers; – Fresh animal manure – Sewage – Compost – Green manure Advantages of organic fertilizers • Micro-organism breakdown organic, releasing nutrient slowly. Hence, nutrients are less likely to be wash out of the soil. • Contains less nutrients per kg, therefore it has a low burn potential and less likely to pollute ground water and rivers. • Contains natural growth factors, which are beneficial to crop plants. Disadvantages of organic fertilizers • Nutrient content not precise depends on materials from which it is made • Organic fertilizers have a low quantity of nutrient per kg it require relatively large quantity to be effective.
This cause organic fertilizers to be bulky, making it more expensive to transport and difficult to apply. • It may contain disease causing organism and/or weed seeds. Inorganic fertilizers These are inorganic salts containing elements required for plant growth manufactured from natural material or synthetic materials. Physical forms of fertilizers • Salts • Pellets • Liquid Soluble forms of fertilizers • Quick release – very soluble form • Slow release – Fertilizer grade Commercial fertilizers are manufactured to contain a precise quantity. The is shown on the container by number which show the grade e. g. 14-28-14. What does 14 – 28 – 14 means?
The fertilizer contains 14% N, 28% P and 14% k. A complete fertilizer contains N, P and K. Incomplete fertilizers supply one or two elements. Examples urea, triple super phosphates and murate of potash. Advantages of inorganic fertilizers • The quantity of nutrient is known • Concentrated source of nutrients • Less bulky • Nutrients are in a more available form, to be used by crops Disadvantages of inorganic fertilizers • They have a high crop burn potential due to concentrated salts. • Excessive use can easily pollute ground water and rivers • Easily leached from the soil. • Excessive use can cause soil to become saline [having too much salt]
Practical activity Identifying types of fertilizers Methods of applying fertilizer • Broad casting • Placement -Circular banding – Row banding • Foliar application • Fertigation Importance of plant sexual reproduction in agriculture THINK OF THE DIFFERENT TYPES OF MANGOES THAT YOU HAVE SEEN OR EATEN. What cause this variation in plants? How does variation in crops (cultivars) benefits agriculture? The flower ? A specialized shoot consisting of reproductive organs ? Structures are arranged in whorls ? A complete flower has four whorls WhorlsOrgans a. Calyx – sepals b. Corolla- petals c. Stamen – filament and anther d. Pistil – Stigma, style & ovary One or more of the structures may be absent( |STRUCTURES |Type of flower | | Calyx |Corolla |Stamen |Pistil | | |( |( |( |- |Staminate | |( |( |- |( |Pistillate | |( |( |( |( |Hermaphrodite | ? Some plants have bisexual flowers only e. g. tomatoes, while others such as cantaloupe, have male and female flowers on the same plant.
Plants such as some cultivars of papaya have male and female on the different plants. ? In addition to reproduction, the flowers of some plants are eaten (broccoli and cauliflower), while many are used for its aesthetic value (anthurium rose and chrysanthemum). Pollination ? Transfer of pollens which contains the male gamete to the stigma ? Pollination is necessary for fertilization ? Fertilization is necessary for the development of true fruits and viable seeds Types of pollinations Self pollination ? Transfer of pollen within a flower or different flowers on the same plant ? Only one plant is involve therefore genetic variation will be reduce ?
Plants produce tends to be more uniform in characteristics. Cross pollination ? Flower are on different plants ? Plants have the characteristics of both parent ? Increase variations e. g. ? Yield ? Shape ? Size ? Increase resistance to disease ? Colour ? Taste ? Important for producing new varieties of crop plants and to improve existing varieties ? Crossing plants of the same species that are not closely related can produce new varieties. The offspring produce are called Hybrids. ? Hybrids tend to perform better than both parents i. e. produce higher yield and are more resistant to pest and diseases. Diagram showing crosspollination [pic]
Fertilization is the joining of the male and female gamete to produce an embryo. The male gamete is found in the pollen grain while the female gametes are present in the ovule. Diagram showing processes involved in seed and fruit formation. [pic] THINK ABOUT IT You may have eaten or head about seed fruits such as oranges and grades. How is possible for these fruits to be formed without seeds. Mas Joe says that the corns he harvested have ‘scattered grains’ i. e. does not have uniforms rows of corn seeds. He believes that this due to the fact that the worker talked a lot during the planting of the crop. Using your scientific knowledge explain to him the true reason why his corns are ‘ scattered grains’ [pic][pic]