Embedded Files
Soil Types
Soil Types
There are wide variations in the types of soils found on farms in Guyana and the Caribbean. The main types of soil with which the Guyana crop producer is most familiar are:
Clay Soils
Sandy Soils
Silty Soils
Loam Soils
Pegasse Soils
No soil is pure sand, pure silt or pure clay. Soils are given the name of the particles that are most predominant.
Sandy Soils in Guyana
Sandy Soils
Sandy Soils
Sand particles are the largest and range in sizes from 0.02 - 2.0 mm in diameter. Sandy soils are light, i.e., they are easy to cultivate. Sand particles have large air spaces between them so the water holding capacity is poor. In wet or humid areas sandy soils are good for the farmer; however, in dry areas they tend to be a liability for the farmer. This is because the water-holding capacity of the soil is low and plants are very liable to 'burn up'. Sandy soils are unstable and can be easily eroded by water (especially on slopes) and by wind. They often need subsoiling at regular intervals to loosen compacted layers (pans) because they have little natural structure. Sub-soiling involves ploughing into the land so as to cut into the subsoil.
Silty Soils
Silty Soils
Silt is similar to sand but the particles are smaller. Silt particles range in sizes from 0.002 - 0.02 mm in diameter. Silty soils are sometimes coated with clay which makes them swell when wet and shrink when dry. Dry silty, alluvial types of soil consist mainly of fine silt and sand particles are are naturally very fertile, found along river banks.
Clay Soils
Clay Soils
Of the three type of soil mentioned, clay has the finest particles. They are less than 0.002 mm in diameter. A soil is classified as clay if it has more than 40% clay particles. Clay soils become sticky when wet and are easily waterlogged. They can hold more water than most other soils types and only half of this is available to plants. However, crops seldom suffer from drought. When dry, they become very hard and this makes it very difficult to cultivate.
A clay soils which is well usually has a better structure and so is easier to work. Clay is normally rich in potash but syffers from phosphate deficiency.
Loam Soils
Loam Soils
Loam soil is composed of almost equal amounts of sand and silt with a little less clay. The best soil texture for growing plants is what is called "loam."1
Among loam's three components—sand, silt, and clay—the sand particles are the largest. Sand does not hold on to moisture, but it provides good aeration and drainage.
On the opposite end, clay particles are much smaller and easily compact. That makes clay a great material for building bricks but not so great for allowing water, air, and plant roots through. However, clay tends to be higher in nutrients than the other soil components.
Silt is the medium-size particle, with better moisture retention than sand but fewer nutrients than clay. Silt helps clay and sand mix together more readily, like tempering chocolate.
Because of the balance of ingredients, loam is the ideal garden soil.1 Its texture is porous, allowing water to flow through slowly enough for the plants to access it but fast enough to avoid waterlogged, soggy soil. Loam is loose and crumbly in our hands. This is referred to as friable. Loose soil provides room for air to mix into the soil, which is also necessary for optimal plant growth. Loam is also nutrient-rich.
For most soils, laying down at least a 2-inch layer of organic matter over the garden surface and then working it into the top few inches of soil each growing season should help to create this ideal soil. Instead of bagging your fall leaves, add them to your garden beds to allow them to decompose and enrich the soil.
Peat Soils
Peat Soils
Peat or pegassy soil is made up of waterlogged partially-decomposed plant material, which have built up over something like 10,000 years in poorly-drained wetland habitats.
The organic matter in peat consists of plant residues that have undergone varying degrees of decomposition. Humus imparts a dark colour to peat.
A distinction is made between weakly decomposed (approximately 20 percent), moderately decomposed (20–35 percent), and strongly decomposed (more than 35 percent) peat. Depending on the conditions under which it was formed and on its properties, peat is classified as high-moor, transitional, or low-moor peat.
Peat has a complex chemical composition, which is determined by the conditions under which peat-forming plants originated, by the chemical composition of the plants, and by the degree of decomposition.
The soils are organic accumulations of peat and other organic matter occasionally interlayered with clay and can be as deep as 9m. They are very acid and have extremely low fertility. Drainage, fertility and acid sulphate toxicity are the main limitations to agriculture. However, with the correct amount of liming this soil type is used to grow sugarcane and other vegetable crops in Guyana. The land cover is mainly natural vegetation of grassland and swamp forest.
Some economic benefits of peatlands
Peatlands bring enormous economic benefits to regions where they are found.
1. Peat is extracted for use as horticultural compost. It is highly sought after in commercial horticulture because of its high water retaining ability and flow of air.
2. Peat is used for fuel to generate electricity. It is also sold as briquettes for heating homes in cold climatic regions.
3. Peatlands are drained and used for agricultural purposes (pasture and crop production) and forestry.
Peat use for forestry and agriculture are beneficial but it alters the natural peatland hydrology. This causes oxidation of stored carbon, therefore, declining its organic matter content. During peat extraction, peat is drained and dried before storage or transportation for sale. These processes reduce the water content and encourage microbial decomposition of organic matter.
N.B.: List AT LEAST three and AT MOST five characteristics of each soil type.
Complete the following Practical Activity on the Soil Types of Guyana.
Importance of Knowledge of Soil Science to the Crop Producer
Importance of Knowledge of Soil Science to the Crop Producer
The soil is the raw material with which the crop producer works and so complete knowledge of the soil is of paramount importance to him/her.
The following are features of soil that are important to the crop producer:
The Chemical Aspect of the Soil
The Chemical Aspect of the Soil
Certain essential chemical elements must be taken up from the soil by plants in order for them to grow and produce crops. The crop farmer must be aware of what nutrients are present or deficient in the soil in order to ensure correct crop growth and production.
Nutrient Functions:
Nutrient Functions:
1. Nitrogen
i) It makes plant dark green & succulent
ii) It promotes vegetative growth.
2. Phosphorus
i) It stimulates root development, increases the number of tillers, gives strength to straw and prevents lodging.
ii) It hastens ripening of plants and counteracts the effects of excessive nitrogen.
iii) It improves the quality and yield of grain.
iv) It increases disease resistance, enhances the activity of rhizobia and increases the formation of root nodules in legumes.
3. Potassium
i) Vigour and disease resistance to plants.
ii) It increases efficiency of the leaf in manufacturing sugars and starch.
iii) It helps to produce stiff straw in cereals and reduces lodging
4. Calcium
i) Increases stiffness of straw and promotes early root development and growth.
ii) It encourages seed production
5. Magnesium
i) It is essential for all green plants.
ii) Helps in uptake of phosphorus and regulates uptake of other nutrients.
6. Sulphur
i) It stimulates root growth, seed formation and nodule formation.
7. Iron
i) Essential for formation of chlorophyll and synthesis of proteins and several metabolic reactions.
8. Manganese
i) It helps in chlorophyll formation.
9. Zinc
i) It helps information of growth hormones and chlorophyll.
10. Copper
i) It regulates respiratory activities in plants.
11. Boron
i) helps in uptake of calcium and its efficient use by plants.
ii) helps in absorption of nitrogen and is necessary in cell division.
12. Molybdenum
i) It is essential for nitrogen fixing organisms both symbiotic and non-symbiotic.
13. Chlorine
i) It is considered essential for photosynthetic process.
Nutrient Deficiency
Nutrient Deficiency
Macronutrients
Calcium (Ca)
Symptoms: New leaves are distorted or hook-shaped. The growing tip may die. Contributes to blossom end rot in tomatoes, tip burn of cabbage and brown/black heart of escarole & celery.
Sources: Any compound containing the word 'calcium'. Also gypsum.
Notes: Not often a deficiency problem and too much will inhibit other nutrients.
Nitrogen (N)
Symptoms: Older leaves, generally at the bottom of the plant, will yellow. Remaining foliage is often light green. Stems may also yellow and may become spindly. Growth slows.
Sources: Any compound containing the words: 'nitrate', 'ammonium' or 'urea'. Also manure.
Notes: Many forms of nitrogen are water soluble and wash away.
Magnesium (Mg)
Symptoms: Slow growth and leaves turn pale yellow, sometimes just on the outer edges. New growth may be yellow with dark spots.
Sources: Compounds containing the word 'magnesium', such as Epson Salts.
Phosphorus (P)
Symptoms: Small leaves that may take on a reddish-purple tint. Leaf tips can look burnt and older leaves become almost black. Reduced fruit or seed production.
Sources: Compounds containing the words 'phosphate' or 'bone'. Also greensand.
Notes: Very dependent on soil pH range.
Potassium (K)
Symptoms: Older leaves may look scorched around the edges and/or wilted. Interveinal chlorosis (yellowing between the leaf veins) develops.
Sources: Compounds containing the words 'potassium' or 'potash'.
Sulfur (S)
Symptoms: New growth turns pale yellow, older growth stays green. Stunts growth.
Sources: Compounds containing the word 'sulfate'.
Notes: More prevalent in dry weather.
Micronutrients
Boron (B)
Symptoms: Poor stem and root growth. Terminal (end) buds may die. Witches brooms sometimes form.
Sources: Compounds containing the words 'borax' or 'borate'.
Copper (Cu)
Symptoms: Stunted growth. Leaves can become limp, curl, or drop. Seed stalks also become limp and bend over.
Sources: Compounds containing the words 'copper', 'cupric' or 'cuprous'.
Manganese (Mn)
Symptoms: Growth slows. Younger leaves turn pale yellow, often starting between veins. May develop dark or dead spots. Leaves, shoots, and fruit diminished in size. Failure to bloom.
Sources: Compounds containing the words 'manganese' or 'manganous'
Molybdenum (Mo)
Symptoms: Older leaves yellow, remaining foliage turns light green. Leaves can become narrow and distorted.
Sources: Compounds containing the words 'molybdate' or 'molybdic'.
Notes: Sometimes confused with nitrogen deficiency.
Zinc (Zn)
Symptoms: Yellowing between veins of new growth. Terminal (end) leaves may form a rosette.
Sources: Compounds containing the word 'zinc'.
Notes: Can become limited in higher soil pH.
Complete the following practical activity on soil nutrients.
The Physical Nature of Soil
The Physical Nature of Soil
Another aspect of soil science in which the crop producer is interested is the physical nature of the soil. He/She needs to know about the texture and structure of soils as they govern the amount of air and water soils can hold. The colour of the soil as well as the slope and vegetative cover are all physical aspects of the soil which are important to the crop producer. The latter will help the crop producer determine whether he/she will have erosion problems or if the land will facilitate mechanization.
The Biological Features of the Soil
The Biological Features of the Soil
THis aspect of soils is important to the crop farmer as he/she must know whether to increasse or decrease the productive capacity of the soil with which he/she is working.
Quiz
Quiz
Complete the following quiz in your portfolio.
List at least three characteristics of each of the following types of soils: (15)
clay
silt
sand
loam
pegasse
Answer T for True and F for False.
Soils are known by the predominant particle present within them. (1)
Knowledge of chemical, physical and biological characteristics of the soil is of little importance to the crop farmer. (1)
Give one reason why knowledge of each of the following is important to the crop producer: (3)
Chemical
Physical
Biological
Total: 10 marks
Discussion
Discussion
Let's do a review of the lesson...
Post under the appropriate topic in the Forums what you learnt, what you would like to learn and what you do not understand.
References
References
Grade 9 SCCP Curriculum Guide
Image of Sandy Soils <https://s1.stabroeknews.com/images/2018/01/Hills.jpg>
Image of Silty Soils <https://www.holganix.com/hs-fs/hubfs/36-1.png?width=1024&name=36-1.png>
Image of Clay Soils <https://www.holganix.com/hs-fs/hubfs/Copy%20of%20WWW-hOLGANIX-COM%20(4)-2.png?width=1024&name=Copy%20of%20WWW-hOLGANIX-COM%20(4)-2.png>
Marie Iannotti. 29/09/2020. What is Loam Soil? The Spruce. <https://www.thespruce.com/what-is-loam-1401908>
NAREI. June 2 2019. Peat Soils. Guyana Chronicle<https://guyanachronicle.com/2019/06/02/peat-soil/>
Montana State University Extension. Plant Nutrient Functions and Deficiency and Toxicity Symptoms. Nutrient Management Self-Study Course. <https://landresources.montana.edu/nm/documents/NM9.pdf>
Page updated
Google Sites
Report abuse