Key Environmental and Soil Factors Influencing Productivity and Management PDF

Key Environmental and Soil Factors influencing Productivity and Management  Topography – reducing surface run-off Rainfall – water supply Soil Limitations – mechanical and engineering structures Soil Condition Productivity – maintaining the soil cover  Topogra...

Key Environmental and Soil Factors influencing Productivity and Management  Topography – reducing surface run-off Rainfall – water supply Soil Limitations – mechanical and engineering structures Soil Condition Productivity – maintaining the soil cover  Topography Slope and aspect are two features of topography that affect soil formation Slope refers to steepness (in degrees or percent) from horizontal and aspect is the direction the slope faces relative to the sun (compass direction). The steepness of the slope affects the amount of deposition or erosion of soil material  The aspect of the slope affects the amount of water that moves through the soil. The north side tends to have more water because of less evaporation and therefore may have more vegetation. The soil chemical processes are slowed on the north aspect because of the colder soil temperatures. A soil with a southern aspect tends to have grass vegetation, warmer soil temperatures, and more evaporation. The net effect is more soil "aging" with a northern aspect when compared to soil with a southern aspect, even with cooler soil temperatures.  Rainfall Precipitation governs water movement in the soil Water movement is influenced by the amount of water the soil receives and the amount of evapotranspiration that occurs.  Soil Limitations Soil pores and water characteristics – proportions of water and air can change rapidly depending on weather, evapotranspiration and other factors Soil fabric, density and strength – solid soil material is arbitrarily divided into fractions, the proportions of which determine the texture of the soil – Bulk density is a measure of the packing or compression of the three constituents of soil. Soil strength is the resistance of soil to shearing or structural failure. Soil structure and crop growth – Increases in soil density or strength retard root penetration and thus limit the volume of soil exploited by the crop and the water available.  Soil Condition The transformation and movement of materials within soil organic matter pools is a dynamic process influenced by climate, soil type, vegetation and soil organisms Without human disturbance, the living and non-living components are in dynamic equilibrium with each other (Mollison and Slay, 1991) – a continuous soil cover of living plants, which together with the soil architecture facilitates the capture and infiltration of rainwater and protects the soil; – a litter layer of decomposing leaves or residues providing a continuous energy source for macro- and micro-organisms; – the roots of different plants distributed throughout the soil at different depths permit an effective uptake of nutrients and an active interaction with microorganisms; – the major period of nutrient release by micro-organisms coincides with the major period of nutrient demand by plants; – nutrients recycled by deep-rooting plants and soil macrofauna and microfauna.  Without human intervention In human-managed systems, the soil biological activity is influenced by the land use system, plant types and the management practices  Productivity Vegetation and biomass production The rate of soil organic matter accumulation depends largely on the quantity and quality of organic matter input. Under tropical conditions, applications of readily degradable materials with low C:N ratios, such as green manure and leguminous cover crops, favour decomposition and a short-term increase in the labile nitrogen pool during the growing season. On the other hand, applications of plant materials with both large C:N ratios and lignin contents such as cereal straw and grasses generally favour nutrient immobilization, organic matter accumulation and humus formation, with increased potential for improved soil structure development. Composition of leaves and roots of leguminous and grass species  Soil characteristics that affect productivity Soil profile and master horizons  Soil physical properties – Color Organic matter—usually black or brown Free iron oxides—usually reddish (in well-drained soils), yellowish brown or orange (in less drained or oxidized soil), or gray to bluish gray (in poorly drained soils) Uncoated mineral grains—usually gray but may be any color depending on the minerals present – Texture Canadian soil texture triangle that uses only two axes to determine soil texture from percentages of sand and clay. Abbreviations for the texture classes: HC, heavy clay; C, clay; SiC, silty clay; SiCL, silty clay loam; CL, clay loam; SC, sandy – Structure – Bulk density and porosity – Water-holding capacity Water is a very important soil component that is required for plant growth and adequate nutrient supply e.g. clayey soils will have a greater water-holding capacity than sandy soils – Temperature Dry soils warm faster than wet soils, especially in the spring. A higher moisture content in surface soil reduces the increase in temperature per absorption of a unit quantity of heat and increases the soil’s thermal conductivity and downward conduction of heat rather than its retention in the surface zone (Hillel 1998) Two soil series: The left soil was formed at the footslope (Webster soil series) while the soil on the right was formed on the shoulder (Clarion soil series).  SOIL PROPERTIES THAT INFLUENCE CONSERVATION (1) soil topography (2) soil depth (3) soil permeability (4) soil horizon and soil series (5) soil structure (6) soil fertility END