NRES 201 Lecture 20 Outline of Last Lecture I. Significance of soil erosionII. Effects of accelerated soil erosionIII. Mechanics of water erosionIV. Predicting water erosionV. Factors affection water erosionOutline of Current Lecture VI. Conservation tillageVII. Significance of wind erosionVIII. Mechanics of wind erosionIX. Factors affecting wind erosionX. Predicting wind erosionXI. Controlling wind erosionCurrent LectureConservation tillage - - What was conventional tillage?o Into the 1980s, conventional tillage for row cropping involved - moldboard plowing to bury residues, disking/harrowing to prepare a clean seedbed, and multiple cultivations to kill weeds.- What changed tillage practices?o Herbicides reduced the need for cultivationo Improved planters - row cleaners allow planting through residue covero Profitability - conservation tillage can increase yields while saving time, fuel, and soil- Conservation tillage systemso Mulch - till Soil surface disturbed by tillage prior to planting Leaves at least 30% residues on or near soil surface Common tillage tools: chisel plows, field cultivators, disks, disk rippers, mulch rippers Weed controls with herbicides or cultivationo Strip - till Tillage confined to narrow strips where rows will be planted Residue left undisturbed between rowsThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute. Strips usually tilled in the fall Requires: Special tillage equipment and precision guidance Weed control with cover crops and herbicideso Ridge - till Soil left undisturbed from harvest to planting Ridges reformed during cultivation of the previous year's crop Declining in usageo No - till Residue cover > 70% Soil left undisturbed except during planting into a 1 - 3 in band created by a heavy duty planter equipped with coulters and row cleaners Weed control with herbicides and/or cover crops Helps conserve soil water Problematic in a cold, wet spring- Value for erosion control - o Demonstrated in hundreds of field trails to compare conventional and conservation tillageSignificance of wind erosion- Mechanicso Detachment - separation of soil grains from aggregates or clods that can occur due to the energy from strong winds. This is far more effective when the wind carries soil particles.o Transportation - Saltation: Moves particles (0.1 - 0.5 mm) in diameter. - Accounts for 50 - 90% of wind erosion- Higher wind speed lowers the pressure above the particle and causes spinning and lifting. Surface Creep: Moves particles (0.5 - 0.84 mm) in diameter.- Accounts for 5 - 25% of wind erosion- Larger particles roll or slide as they are bumped along the land surfaceo Suspension - Soil particles up to fine sized sand are carried upward as wind speeds increase above the land surface. o Deposition - Saltating particles usually deposited in the vicinity of the eroding fieldFactors affecting Wind erosion- Wind factors - o Velocity: Usually measured at a height of 10 mo Turbulence: Irregular mixing of air moving at different speeds. It enhances soil suspension and movement.o Gustiness: Gusty winds are much more erosiveo
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