PDS AP Environmental Science 8th Period 2010-11

If swamps can naturally clean waste water, wouldn’t that hurt the ecosystem of the swamp because run-off and feces from waste water will provide nitrogen, and thus start the process of Eutrophication?

Also, isn’t cleaned waste water and drinking water basically the same thing except drinking water has had chlorine added to it?

Many common problems affect soil around the world on a daily basis. The ones we covered in class are: desertification, salinization, water logging, and reduced fertility.

DESERTIFICATION-

Desertification is mainly due to drought, but human activity can also speed up the process. Whenever humans plow, overgraze, deplete water sources, and so on, they run the risk of desertification of marginal lands, or grasslands close to a desert. The desert expands into the marginal lands because human activities remove the plants that hold the soil and keep the water in place, and the wind blows the soil away, leaving desert conditions.

Above: a farmer examines his once fertile soil–now cracked and unusable.

Desertification affects 250 million people worldwide. How can we stop it? We can use different planting techniques such as low till, no till, or greenbelts (also known as agroforestry).

Watch this video about desertification and its role in the world right now

SALINIZATION

Salinization–as we learned in our first lab this year–occurs when there is too much salt in the soil for plants to live. Salinization is caused from over-irrigation, and is a problem for 20% of our farmlands worldwide. When soil is over-watered, the water evaporates more quickly from the soil. As the water rises through the soil, it carries salt, and as it evaporates, it leaves the salt deposited on the surface.

The white spot on the field is an aerial view of a salt covered field

Since it’s too expensive for most farmers to filter their water of salt, other preventions are reducing the amount of irrigation or switching to drought tolerant crops so not as much irrigation is needed. As far as cleanup, farmers can attempt to flush their soil, stop growing, or create an underground draining system if salinization is already a problem.

WATERLOGGING

1/10 if all cropland is affected by waterlogging, which occurs when farmers attempt to flush their soil and leach salt deeper. Instead of getting rid of the salt, they accidentally raise their water tables so that extra water sits in the soil, drowning the roots of their crops. This lack of oxygen can cause root rot–a fungal disease.

Left: Waterlogging has caused excess water to sit on the surface and drown the plants

REDUCED FERTILITY

(The other three soil problems are physical, but reduced fertility is a chemical problem.) Reduced fertility , or not enough nutrients in the soil, can be fixed by either organic or inorganic fertilizers.

Organic fertilizers help build soil structure and organic matter (humus), but do so very slowly because they depend on bacterial decomposition.There are three types: compost (plant matter), animal manure, and green manure (legumes ground into the soil to increase nitrogen levels due to the nitrogen fixing bacteria in their roots).

Inorganic dissolve quickly and are precise doses of certain chemicals, but they don’t help build soil composition, and they create pollution problems when they leach through the soil and contaminate groundwater or evaporate into the air and cause air pollution.

Check out this website for the advantages and disadvantages of inorganic fertilizer (as shown in pic)