Soil degradation, conservation, and improvement Topic 5 Part 2

Soil degradation and loss

Soil conservation methods These methods help to reduce erosion (loss of topsoil)  No-till  The soil is not turned over at all/left undisturbed. Farmers use a machine to insert seeds into the ground.  Low-till/minimum till  the soil is disturbed as little as possible and crop residue is left in the fields to cover bare soil (minimizes erosion by wind)  No-till  The soil is not turned over at all/left undisturbed. Farmers use a machine to insert seeds into the ground.  Low-till/minimum till  the soil is disturbed as little as possible and crop residue is left in the fields to cover bare soil (minimizes erosion by wind)

More conservation methods  Terracing  Cutting terraces (flat regions) into hillsides. This reduces downhill erosion by giving soil in flat areas time to absorb rain water, decreasing soil erosion by water run-off)  Contour plowing  Plows in rows that follow the curve of a hill. This slows water run-off and thus reduces erosion.  Terracing  Cutting terraces (flat regions) into hillsides. This reduces downhill erosion by giving soil in flat areas time to absorb rain water, decreasing soil erosion by water run-off)  Contour plowing  Plows in rows that follow the curve of a hill. This slows water run-off and thus reduces erosion.

More cons. methods  Polyculture  Planting different crops in alternating strips (one is usually low to ground and the other tall) to reduce water run-off and wind erosion)  Agroforestry  Planting crops in strips between trees to reduce wind erosion  Windbreaks/shelter belts of trees  Surrounding fields with trees to reduce wind erosion  Polyculture  Planting different crops in alternating strips (one is usually low to ground and the other tall) to reduce water run-off and wind erosion)  Agroforestry  Planting crops in strips between trees to reduce wind erosion  Windbreaks/shelter belts of trees  Surrounding fields with trees to reduce wind erosion

Even more cons. methods  Rotating crops with ground cover plants  After each crop, plant fast growing vegetation (this could even be another type of crop) so that the ground is always covered with something to reduce wind erosion  Protect riparian (fancy word for riverside) buffer zones  Prevents soil loss by erosion into rivers. Also protects the crop fields from flooding events  Grazing rotation  Rotate grazing animals between fields so that they do not eat all the vegetation in one area, leaving bare ground that is vulnerable to erosion.  Rotating crops with ground cover plants  After each crop, plant fast growing vegetation (this could even be another type of crop) so that the ground is always covered with something to reduce wind erosion  Protect riparian (fancy word for riverside) buffer zones  Prevents soil loss by erosion into rivers. Also protects the crop fields from flooding events  Grazing rotation  Rotate grazing animals between fields so that they do not eat all the vegetation in one area, leaving bare ground that is vulnerable to erosion.

Improving soil quality  Crops remove nutrients from the soil.  Fertilizers are used to replace those nutrients.  Farmers can use either organic or inorganic fertilizers  Crops remove nutrients from the soil.  Fertilizers are used to replace those nutrients.  Farmers can use either organic or inorganic fertilizers

Organic fertilizers Advantages  Help to build up the soil quantity (essentially humus material)  Result in slow, long-term release of nutrients to the soil through bacterial breakdown  Cheap to use if the farmer has lots of compost or manure Advantages  Help to build up the soil quantity (essentially humus material)  Result in slow, long-term release of nutrients to the soil through bacterial breakdown  Cheap to use if the farmer has lots of compost or manure Disadvantages  Takes longer to release nutrients than commercially produced fertilizers  Is dependent on having healthy bacterial communities in the soil  Expensive to use if the farmer does not have a source of manure or compost Disadvantages  Takes longer to release nutrients than commercially produced fertilizers  Is dependent on having healthy bacterial communities in the soil  Expensive to use if the farmer does not have a source of manure or compost Partially decomposed organic material (compost or manure)

Inorganic fertilizers Advantages  Quick, concentrated source of plant nutrients (easy to buy and easy to use)  Easy way to improve soil fertility  Cheaper than organic fertilizers to purchase  Crops can use the nutrients right away (no waiting for bacteria to break them down)  Increases crop growth and yield  Guaranteed amount of nutrient (easily quantifiable) Advantages  Quick, concentrated source of plant nutrients (easy to buy and easy to use)  Easy way to improve soil fertility  Cheaper than organic fertilizers to purchase  Crops can use the nutrients right away (no waiting for bacteria to break them down)  Increases crop growth and yield  Guaranteed amount of nutrient (easily quantifiable) Disadvantages  Does not add to the organic material content of the soil  Can decrease water holding capacity  Does not supply all of the trace elements necessary for plant growth  Requires lots of energy to produce  Releases N 2 O, a greenhouse gas  Contributes to cultural eutrophication when run-off occurs  Can be very expensive to purchase Disadvantages  Does not add to the organic material content of the soil  Can decrease water holding capacity  Does not supply all of the trace elements necessary for plant growth  Requires lots of energy to produce  Releases N 2 O, a greenhouse gas  Contributes to cultural eutrophication when run-off occurs  Can be very expensive to purchase Commercially produced solutions of phosphate and nitrate.

Soil testing methods

Physical tests  Soil sieve test  Percolation rate  Color  Soil sieve test  Percolation rate  Color  Used to determine ratios of particles (texture) and then soil type (using what?)  Measures the speed of infiltration of water into soil  Can indicate soil components like humus, iron compounds

Chemical tests  pH  Nutrient measures  Metal measures  Cation exchange capacity  pH  Nutrient measures  Metal measures  Cation exchange capacity  Measures the acidity or alkalinity of the soil  Measures the amount of nitrogen (as nitrates), phosphorus (as phosphates), potassium, or sulfur  Measures the amount of heavy metals like iron, cobalt, aluminum, mercury, etc.  Measures the ability of soil to absorb and release cations that are necessary for plants (like calcium, potassium, magnesium)

What do farmers/garderners use this info for?  Ways to improve soil for crop/garden growth that will ensure sustained growth over time  Scenarios:  You find that your soil is very acidic. What can you add?  You find that your soil texture is predominantly sand. As a consequence it has low water holding capacity and poor nutrient holding capacity. What could you mix in?  You find that your soil in low in nitrates. What could you plant to help this situation in the long term?  You find that your topsoil has very little humus and is thin. What could you add?  Ways to improve soil for crop/garden growth that will ensure sustained growth over time  Scenarios:  You find that your soil is very acidic. What can you add?  You find that your soil texture is predominantly sand. As a consequence it has low water holding capacity and poor nutrient holding capacity. What could you mix in?  You find that your soil in low in nitrates. What could you plant to help this situation in the long term?  You find that your topsoil has very little humus and is thin. What could you add?