Irrigation & Sustainable Agriculture PDF

5.5 Irrigation & Sustainable Agriculture How do the practices of tilling and plowing influence erosion? Methods of Reducing Soil Erosion Contour plowing Terrace farming Windbreaks Strip cropping Intercropping Cover Crops Sustainable Agriculture: Contour Plowing Following the contou...

5.5 Irrigation & Sustainable Agriculture How do the practices of tilling and plowing influence erosion? Methods of Reducing Soil Erosion Contour plowing Terrace farming Windbreaks Strip cropping Intercropping Cover Crops Sustainable Agriculture: Contour Plowing Following the contours of the topography when plowing the field. Reduces runoff and Erosion Sustainable Agriculture: Terracing Transforming slopes into series of steps to create flat places to farm. Allows cultivation on steep landscapes and slows runoff/erosion. Sustainable Agriculture: Windbreaks Using structures (often trees) to slow down wind flow across the fields. Reduces wind damage to crops and erosion of dirt from fields. Sustainable Agriculture: Strip Cropping Growing diff erent crops in strips which may be alternated each year in crop rotation. Can help prevent largescale pest/disease outbreaks. Agriculture: Intercropping Growing multiple crops alongside or on top of each other. Corn: supports the beans Beans: add nitrogen Squash: shades out weeds. Sustainable Agriculture: Cover Crops Plants planted with the purpose of covering exposed soil rather than for harvesting. Often used during the off season of fields to prevent erosion and loss of soil nutrients. Irrigation: The Majority (70%) of Freshwater around the world is used for Irrigation. Adding water into fields for the use of growing crops. How much does this impact? 60% of agriculture is rainfed & dependent on local weather. These farms use 80% of our total cultivated land to produce 60% of the food. The 20% of our cultivated land that is irrigated produces 40% of the calories we consume.  Flood Irrigation: ~20% of water lost to Completely fills the field with water. evaporation Good for water-loving crops like rice High risk of Waterlogging: Soil is fully saturated creating anoxic conditions and risking rotting plant roots. High risk of soil salinization  Furrow Irrigation: Small ditches filled with water around crops on raised bed. Inexpensive Not great for sandy soil More precise water delivery to crops compared to flood ~33% of water lost to evaporation  Spray Irrigation: Water is sprayed into the air and falls onto the crops like rain. Supplements/Fertilizer can be added into the water Can be set on a timer More expensive than Flood or Furrow ~25% of water lost to Machinery run with fossil fuel use evaporation Sprinkler Systems stay in place. Pivot Systems move across the field. What makes those circles? https://www.youtube.com/watch?v=tlDfSqAz11s Drip Irrigation: 2-5% of water lost to evaporation! Water is distributed through garden hoses with holes to deliver water directly to the crop roots. VERY expensive to set up. (Each crop must have a hose next to it) Rodents may chew and damage the hoses. Clogs easily Placement makes other processes difficult Comparing Irrigation Methods Method Water Energy Setup Cost Efficiency Efficiency Flood 40 – 65% Low – High Low Furrow 50 – 75% Low – High Low Spray 70 – 95% Medium High Drip 90 – 97% High High  Issues with too much Irrigation: Depletion of Aquifers As we mentioned last unit, using water faster than it can be “recharged” into the aquifer can lead to depletion of the aquifers like the Ogallala.  Issues with too much Irrigation: Waterlogging If too much water is applied via irrigation, it can oversaturate soils, creating anerobic conditions and preventing the normal gas exchange between plant roots and the gasses in the soil. This weakens and often kills plants.  Issues with too much Irrigation: Salinization: salts from the water build up in soil as water evaporates. The higher the salt content in the water, and the higher the evaporation, the faster this happens. Soil with too much salt cannot grow plants as the water is more attracted to the salty soil than the plant.