Soil and Food

1. Soil and Food Lecture 7 EB 2008

2. Agenda • Two fold • 1) Understanding soil • 2) Understanding farming and food production

3. Case Study A • No-Till farming in Brazil • Started in Southern Brazil • Tried to follow the European method of farming - plowing and planting • Failed - resulted in erosion - soil was washed or blow away • Had to find alternative… • No-Till farming = leave it alone… • Reduced erosion by 90%

4. Tilling No-till farming

5. Soil & farming • Agriculture = practice of raising crops and livestock for human use and consumption • Cropland = land used to raise plants • Rangeland = land used for grazing livestock

6. Traditional vs. Industrialized • Traditional Agriculture = still uses man or animal power, with simple tool use • Industrialized Agriculture = use of powerful machines and synthetic fertilizers

7. First farmers • In human history • We started agriculture about 10,000 years ago • It seems that lots of tribe go the same idea about the same time…

10. Modern agriculture = more food • 38% of the landmass of the planet is used for agriculture • It is going to be hard to use the rest • Living land • Sensitive land • Unsuitable for some other reason • ??? • So we have to use this 38% more efficiently • However, bad practices lead to more problems. • Run off, deforestation, desertification, pollution (air, land, water), toxic chemicals, erosion, etc.

11. EB’s need to understand Soil • Soil is complex and heavily infiltrated by living things. • 2 parts • Inorganic matter • Granulated rock • Minerals (50%) • Gases • Water (45%) • Biotic component (5%) • Bacteria • Fungi • Waste • Dead matter

12. Soil formation is slow and complex • Rocks are weathered into soil

13. Horizons? - Soil profiles • Over time distinct layers develop • These layers are known as horizons • The total profile from top soil to bedrock is known as a soil profile…

14. The uppermost layer (the O horizon, or litter layer) consists mostly of organic matter deposited by organisms. • Below it lies the A horizon, or topsoil, consisting of some organic material mixed with mineral components. • Minerals and organic matter tend to leach out of the E horizon down into the • B horizon, or subsoil, where they accumulate. • The C horizon consists largely of weathered parent material unaltered or only slightly altered by the processes of soil formation. • The C horizon may overlie an R horizon of pure parent material.

15. Layering • Material moves from one layer to the next via leaching - carried by water • This can be slow or very fast • Sometimes too fast and the soil cannot support plant life…

16. THINK! • It can take hundreds to thousands of years to produce just 1 inch of topsoil. • Do you think such a resource should be considered ‘renewable’? • How would you define a ‘renewable resource’? • How do you think soil’s long renewal time should influence its management? • What types of practices encourage the formation of new topsoil?

17. Soil can be characterized by color, texture, structure, and pH • The color of soil can indicate its composition and sometimes its fertility. • Black or dark brown soils are usually rich in organic matter, whereas a pale gray to white color often indicates leaching or low organic content.

18. Soil can be characterized by color, texture, structure, and pH • Soil texture is determined by the size of particles and is the basis on which the United States Department of Agriculture (USDA) assigns soils to one of three general categories • Clay consists of particles less than 0.002 mm in diameter, • Silt of particles 0.002ﾐ0.05 mm, and • Sand of particles 0.05ﾐ2 mm. • Sand grains, as any beachgoer knows, are large enough to see individually and do not adhere to one another. Clay particles, in contrast, readily adhere to one another and give clay a sticky feeling when moist. • Soil with a relatively even mixture of the three particle sizes is known as loam.

20. Soil structure is a measure of the “clumpiness” of soil. Some degree of structure encourages soil productivity, and biological activity helps promote this structure. • pH - The degree of acidity or alkalinity influences a soil’s ability to support plant growth.

21. Regional differences in soil traits can affect agriculture • Soil characteristics and soil profiles vary from place to place • Given a choice would you like to establish your farm in the Amazon with its lush forest, or in the central valley here?

22. Different environments - different outcomes Erosion Desertification Salinization Waterlogging nutrient depletion structural breakdown pollution.

23. Erosion can degrade ecosystems and agriculture Erosion is the loss of topsoil… • Overcultivating fields through poor planning or excessive tilling • Overgrazing rangelands with more livestock than the land can support • Clearing forests on steep slopes or with large clear-cuts

24. Soil erodes by several mechanisms • Removing plant cover nearly always accelerates erosion • Several types of erosion can occur, including wind erosion and four principal kinds of water erosion • Splash erosion occurs as raindrops dislodge soil particles that fill in gaps between remaining clumps, decreasing the soilﾕs ability to absorb water. • sheet erosion, water flows in thin sheets over broad surfaces, washing topsoil away in uniform layers. • rill erosion, water runs along small furrows, deepening and widening them into channels called rills. Rills can merge to form larger channels and eventually gullies. • Gully erosion(d) cuts deeply into soil, leaving large gullies that expand as erosion proceeds.

25. Food Production

26. Facts of life… • The population is expected to hit 9 billion by 2050 • We have been able to produce food faster than population growth (so far) • Still… • 13% of the population is hungry • Some are undernourished • Others suffer from malnutrition • Someone dies every few seconds • Some are overnourished • Fat (3/5) • Obese (1/4) • Heath effects, shorter life spans, expensive solutions.

27. Bad Practices in Agriculture • In the past people used polyculture… • Now over 25% of our farmland is monoculture… • We are seeing signs that there is a reduction in the food yield compared to the bumper crops of 1985 • Soils are in decline and pollution on the increase. • What will happen in the next 40 years?

28. Green revolution • The introduction of industrialized agriculture to the developing world. • Designed to increase yields per acre • However, total yields rose 33% between 1900 and 2000 • But consumption of energy to get these gains by 800% • Had both positive and negative outcomes. • Is this worth it?

29. Pest and Pollinators • Pest - are organisms that damage our crops • Weeds - are plants that compete with our crops • Widespread use of chemicals to control these • Insecticides • Pesticides • Herbicides • Fungicides • Since 1960 the use of pesticides has shot up 400%

30. Evolution of Resistance • Chemicals may not kill 100% of the pests. • Those that survive will have babies that are also resistant. • This will negate the effects of the chemicals very quickly • Biological controls have the same outcome..in some cases • Prickly pear example. • Better weapon is IPM (Integrated pest management) - a custom solution to each problem.

31. Insects are important • Plants may be wind pollinated or insect pollinated. • Bees and the like perform pollination • Remove the bees and we have a problem…

32. GM foods • Genetic engineering of plants and animals to aid us with food production • Manipulate the DNA of the organism • GM - Genetically Modified • Place genes for desirable traits into our crops and livestock.

33. Feedlot Agriculture • More wealth equals a greater demand for meats. • Feedlots = factory farms = churn out meat by intensive, density driven, high calorie diet feed. • Reduce impact on the environment, but only of managed properly • In the future we may have to give up meat every day!!! • Energy loss from one trophic level to the next is at 90%. • Land and water equivalents have been calculated…

34. In you books there are some great figures comparing The amount of feed input per kg of produce The amount of land needed to produce produce The water usage per kg of produce Please look these over for next weeks quiz…

35. Sustainable Agriculture • A form of farming that does not deplete resources - land or water. • Still uses low amounts of pesticides, fertilizers, growth hormones, etc. • Organic farming uses none. • More people are turning to organic produce.

36. Conclusions • Which way to go… • How best to feed the growing population, without destruction of both the soil or the environment. • A solution must be found now, before the collapse of agriculture.