NRES 201 Lecture 20 Outline of Last Lecture I Significance of soil erosion II Effects of accelerated soil erosion III Mechanics of water erosion IV Predicting water erosion V Factors affection water erosion Outline of Current Lecture VI Conservation tillage VII Significance of wind erosion VIII Mechanics of wind erosion IX Factors affecting wind erosion X Predicting wind erosion XI Controlling wind erosion Current Lecture Conservation 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 cultivation o Improved planters row cleaners allow planting through residue cover o Profitability conservation tillage can increase yields while saving time fuel and soil Conservation tillage systems o 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 cultivation o Strip till Tillage confined to narrow strips where rows will be planted Residue left undisturbed between rows These 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 herbicides o Ridge till Soil left undisturbed from harvest to planting Ridges reformed during cultivation of the previous year s crop Declining in usage o 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 tillage Significance of wind erosion Mechanics o 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 surface o 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 field Factors affecting Wind erosion Wind factors o Velocity Usually measured at a height of 10 m o Turbulence Irregular mixing of air moving at different speeds It enhances soil suspension and movement o Gustiness Gusty winds are much more erosive o Direction
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