Lecture 9 Management of Major Soil Types in Guyana PDF

Management of Major Soil Types in Guyana Coastal Clays  Inceptisols, Entisols and Histosols  Inceptisols include the Frontland Clays and soils of the Coropina Formation  Entisols include some Frontland Clays and soils in riverain regions  Histosols are...

Management of Major Soil Types in Guyana Coastal Clays  Inceptisols, Entisols and Histosols  Inceptisols include the Frontland Clays and soils of the Coropina Formation  Entisols include some Frontland Clays and soils in riverain regions  Histosols are found 5 – 10 km inland, behind the Frontland Clays  These soils are generally characterized by high clay content with varying levels of montmorillonite, illite and kaolinite  Topographically the entire region is low-lying, flat to gently undulating and in some parts below sea level  Management of Major Soil Types in Guyana Coastal Clays  Frontland Clays: Most recently deposited alluvial soils; primarily clayey in texture but interspersed with sandy loams  Marine origin from the pre-Quaternary geological era  Medium to high base status with pH ranging from 5.0 to 8.0  Closer to the ocean, saline soils may be found  These soils are utilized mainly for rice, sugarcane and vegetable production but are also suitable for a much wider range of crops including perennials  Management of Major Soil Types in Guyana Coastal Clays  The Coropina Formation: Occur in low-lying areas on flat or nearly flat topography and in situations with high rainfall  Usually show excessive leaching of plant nutrients and migration of clay from surface layers to lower depths  Relatively light texture surface layer dominated by silt and fine sand and very dense and compact subsurface horizon.  These soils may be found to the south of the Frontland Clays but north of the Histosols  Generally utilized for rice and sugarcane production but are underutilized in the main Management of Major Soil Types in Guyana Coastal Clays  Management of Major Soil Types in Guyana Climatic Features  Annual rainfall of ~ 2250 mm has a bimodal distribution with ~ 60% occurring in April – August and less than 30% between November – January  Along the coastline, mean annual rainfall is known to increase from east to west  Mean air temperature ranges between 25 to 27.5°C throughout the year with diurnal variations of less than 5° C Climate Change Solutions International (CCSI, 2009) noted that the mean annual air temperature of Guyana, overall, as increased by 0.3°C since 1960 Management of Major Soil Types in Guyana  Management of Major Soil Types in Guyana Implications for Agriculture  Region is prone to periodic flooding  Drainage is a requirement  High rainfall makes water control a necessity  Topography presents a serious challenge  Abundant water resources make irrigation possible  Fine textured soils may require conventional tillage for some crops  Conservation tillage not extensively practised but may be of value in soils of the Coropina Formation  NPK fertilizer application along with periodic liming appears to be generally required  Management of Major Soil Types in Guyana Acid Sulphate Soils  Acid Sulfate soils (ASS) are naturally occurring soils and sediments containing iron sulphides, most commonly pyrite (FeS₂)  They are extremely acidic soils and are safe and harmless when undisturbed and in a waterlogged state  When exposed to air the iron sulphides react with oxygen and water to produce iron compounds and sulphuric acid  In Guyana, an example of ASS can be found in the Potoco swamps of the Canje Basin  Management of Major Soil Types in Guyana Acid Sulphate Soils Potential Acid Sulphate Soils: Often have a pH close to neutral (6.5-7.5). Contain unoxidized iron sulphides. Are usually soft, sticky and saturated with water. Are generally gel-like muds but can include wet sands and gravels. Have the potential to produce acid if exposed to oxygen.  Management of Major Soil Types in Guyana Acid Sulphate Soils Actual Acid Sulphate Soils: Have a pH of less than 4. Contain oxidized iron sulphides. Vary in texture. Often contain jarosite ( a yellow mottle produced as a by-product of the oxidation process)  Management of Major Soil Types in Guyana Acid Sulphate Soils Management Options  Start with identifying the depth of the sulphuric horizon 1. In cases where it may be too risky to drain these soils, they should be left undisturbed 2. If the sulphuric horizon is located well below (˃ I metre below the surface) it may be possible to drain to that depth and use the soil volume above 3. If it is determined that acidification is likely to be limited, soil may be drained and limed to achieve a manageable pH 4. In some cases it may be necessary to induce flooding to maintain the soil in its original state