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2 Soil Resources and Sustainable Agriculture Ways We Use and Abuse Soil –Erosion Other side effects of Agriculture Toward Sustainable Agriculture

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5 Erosion NATURAL PROCESS! Part of Rock Cycle What are the mechanisms for erosion? –Water –Wind –Chemical –Heavy machinery and trampling

6 Fig Percent of Agricultural Lands with Human-caused Soil erosion Percent of World land area Affected by Erosion types

7 Water and wind erosion Figure 10.11

8 CS Fig 10.10

9 Erosion Worldwide, effects same as removing 1% of cropland each year!

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11 Figure 10_09

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13 Is it a coincidence that areas of remaining Frontier Forests and areas of stable soils overlap?

14 Soil Erosion: Where do we stand? Until the 1980’s, new land brought under cultivation compensated for soil loss. Since the 1980’s, land under cultivation has been declining –Peak Soil!? We use 1/10 th of the Earth’s land surface to grow crops and 1/4 for grazing. There is little suitable land left for expanding either. Where is the main place left to expand? –Is this a good idea?

15 Easter Island? Worldwide, 38% of cropland moderately to severely degraded (UN) Worldwide, erosion losses same as removing 1% of cropland each year! Population is rising –With population rising and soil declining, does that provide an incentive to think long term or short term? Worldwide ~70 cm of topsoil left on average –How long will this last?

16 Soil Erosion: What can we do? Practice no-till agriculture –Use disk to mix organic matter into soil surface –Leave crop residue on ground –Plant seeds with chisel plow (punches seeds past residue) –23% of US agriculture and growing! Practice polyculture –Plant complimentary crops that cover the ground surface for more of the year –Plant crops that enrich the soil (symbiotic with Nitrogen fixing bacteria) like legumes, alfalfa Use composted manure (animals important!!) –Only way to actually build up the soil!

17 No till agriculture Figure Soybeans growing in corn mulch

18 FOOD SUPPLIES World food supplies have more than kept up with human population growth over the past two centuries. – billion people - average daily diet was less than 2,000 calories/person. – billion people - world food supply can provide more than 2,500 calories/person.

19 The Green Revolution The result of development of High Responders through agricultural research New plants allow high yield, yet require optimal conditions Made it possible for world food production to keep up with world population CS Fig 9.18

20 The Green Revolution Started only 50 years ago Dwarf wheat one of earliest developments (earned Norman Borlaug the Nobel Prize) CS Fig 9.17

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22 Farmers get the “Big Squeeze” New varieties require optimal conditions –Farmers must be able to afford expensive seeds, fertilizers, irrigation methods, etc. If farmers can’t afford these things, the regular varieties won’t produce enough yield to keep them in business Big business farming wins long-term

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25 Pesticides Carcinogens affect humans and wildlife Insects become resistant, requiring more pesticides!

26 Table 10_01

27 Modern vs. Sustainable Farming Modern methods fight against natural processes –Soil loss requires increasing amounts of fertilizer, Pesticide use escalates, creates vicious cycle Sustainable methods work with natural processes Diversification is key Soil erosion reduced, nutrients replenished naturally, need for pesticides reduced (natural microbes much higher) –Natural fertilizer (manure, crop rotations) Can Sustainable methods feed the world? –YES! –Why? They have to.

28 Analysis Sustainable/organic farming advantages –Use 1/3 to ½ of fertilizer, energy used in conventional methods –Use virtually no pesticides –Soil condition improves instead of degrades –Same to 20% lower harvests, but with lower costs, profits are same or better

29 Farm Subsidies Complicated economic issue! –Subsidies at home, tariffs at home and abroad Eyebrow raising fact: –1/10 th of producers get 2/3 of the subsidies –Lobby hard to keep subsidies

30 Genetic Engineering CS Fig 9.19

31 The Role of Genetic Engineering? The next wave of the Green Revolution? The Good: less pesticide use required, poor soils could be productive The Bad: more herbicide use possible, “contamination” of wild species, lowered pest resistance CS Fig 9.20

32 It’s already begun Current GMO’s –82% of all soybeans –71% of cotton –25% of corn 60% of processed food in America has GMO ingredients – YOU’RE EATING THEM ALREADY!!

33 GMO’s: The big scam? The National Academy of Sciences’ Agricultural Board found that GMO soybeans give smaller harvests than natural seeds in over 8,000 trials! The US Department of Agriculture found that there was no reduction in pesticide use, even though a decrease in pesticide use was advertised as being a benefit GMO and high-yield seeds are proprietary. The companies can sue you if some of the plant seeds itself because you didn’t pay for that seed. A farmer in Canada fought and won, but many don’t fight.

34 The End. Back