Sustainable Agriculture Practices: Enhancing Crop Health and Yield

1. Feeding the World

2. Magnesium • Also absorbed in +2 ion form • Essential in the formation of chlorophyll

3. Cells deficient in magnesium will have yellow spots where chlorophyll is not produced • Chlorosis – the collective term for a plant deficient in either nitrogen, magnesium, or iron

4. Sulfur • From the negatively charged sulfate ion • SO42- • Used in methionine and cysteine (two very important amino acids) • Also used in Coenzyme A, an enzyme used in respiration and the synthesis and breakdown of fatty acids and vitamins

5. Comes from volcanoes and the burning of wood (sulfate is a pollutant that plants remove from the environment)

6. Fertilizers • As plants consume the nutrients in the soil we have to replace them • Fertilizers replace the missing nutrients

7. Straight fertilizer – contains only one nutrient • Mixed fertilizer – contains N, P, K and rated by their percent abundance in the fertilizer • 6-12-12 • 30-15-6

8. Compost generally has a much lower NPK rating but helps to aerate the soil and retain the nutrients • The usual NPK for compost ranges from • 0.5-0.5-0.5 to 4-4-4 • So if the NPK rating of compost is so low why do some people consider it the better fertilizer?

9. Damage control • Each year thousands of pounds of food crops fall victim to natural predators • Over the years many advances in crop protection have been made

10. The three most damaging predators of crops are insects, other plants, and fungi

11. Insects • There are thousands of species of insects and many are very beneficial • Without honey bees it would take billions of dollars to pollinate all of our crops

12. However some insects feed on crops and thus must be controlled • Aphids • Mites • Worms

13. Pesticides • 3 main types exist • Chlorinated hydrocarbons • Organophosphates • Carbamates

14. Chlorinated Hydrocarbons • Excellent longevity – they remain active for months to years • Nonpolar – not water soluble so they will not wash off from rain • Usually not biodegradable – no existing biochemical pathway exists to break down these molecules

15. DDT • DDT - dichlorodiphenyltrichloroethane

16. Benefits • Used in the 1940s and 50s • Showed excellent control of insect populations • Added to water supplies to control mosquitoes, lice, tsetse flies • Very high crop yields for about 10 years

17. The down side • Bioaccumulation – the buildup of chemicals through the food chain • DTT is fat soluble

18. DDT resistant insects appeared • DDT was banned in the early 70s • However many third world countries still use it today

19. Alternatives • Methoxychlor

20. Organophosphorus and Carbamates • Both are readily decomposed by water • Short lived effect on crops • Very toxic to insects as well as animals • Detrimental to honey bees as well

22. Herbicides • 600 million pounds used per year in the US • Selective herbicides developed to kill weeds but not harm plants

23. Agent Orange • 2,4-dichlorophenoxyacetic acid (2,4-D) • 2,4,5-trichlorophenoxyacetic acid (2,4,5-T) • TCDD is a byproduct of making the previous compounds

24. Mimic plant growth hormones and are selective to broad leaf plants • this leaves grasslike crops such as corn and wheat alone • 2,4,5-T discontinued in 1985 because of TCDD contamination

25. Alternatives • Atrazine – toxic to common weeds but grasslike crops can metabolize it (detoxify) • Paraquat – kills weeds during the sprouting phase • Glyphosate – nonselective herbicide, targets the biosynthesis of tyrosine and phenylalanine • Low toxicity in animals • Round-up

27. Fungicides • Fungi are very necessary to decompose dead matter but often spoil harvested crops (particularly fruits) • Annually 100 million pounds are used in the US

29. Root rot – besides damaging harvested crops fungi can also damage root systems of plants • Generally happens when excess water is present

30. Improvements • Crop production has greatly increased over the past 100 or so years • These improvements also have some disadvantages

31. Pesticides and herbicides are toxic and thousands of workers yearly are treated for exposure • A portion of every fertilizer is washed away to streams, river, lakes, and ponds and upsets the ecosystem there

32. Fertilizer runoff can also contaminate our drinking water supply • Excess nitrate ions in drinking water compete with oxygen in our blood

33. Loss of topsoil • Plowing under weeds • Use of synthetic fertilizers not compost • 1930s

34. Irrigation problems • Flooding • Sprinklers • Evaporation

35. Excessive use of underground water • Land subsidence

36. Salination of the Soil • Flooding and irrigation lead to increased salts in the soil • Too much salt is detrimental to plants • The further from fresh water the more salt in the soil

38. Better Methods • Excessive fertilizer and pesticide use is bad for topsoil, crops, and our health • We need to protect the topsoil and fresh water sources

39. Better Irrigation • Microirrigation – supplies water directly to plant roots • Benefits • Reduces evaporation • Reduces soil salinization • Prevents topsoil erosion

40. Organic Farming • - use of only naturally occurring chemicals • Crop rotation • Corn>Legume>Corn • Natural fertilizer • Compost/manure • Natural insect control • Predators (birds, spiders, snakes)

41. Organic farming uses less than half the energy of traditional farming • Much of the energy saved is in the production of fertilizers/pesticides/herbicides • The US uses 300 million barrels of oil to produce nitrogen fertilizers

42. Is organic food better for human consumption?

43. Integrated Crop Management • Managing crops profitably in an area while conserving resources • Use of crop rotation or multicrop fields • Intermix a legume with a non nitrogen producing plant • Reduces pests and increase soil fertility

44. Planting only crops that suit a particular climate

45. Integrated Pest Management • Also uses crop rotation • Plant trees and bushes around or in fields to provide a natural habitat for insect predators • Use plants that are naturally resistant to certain pests • Use hearty crops that can out compete weeds

46. GPS helps target pesticides and fertilizers • Pests can also be hand picked off of plants • Weeds can be plowed under the soil

47. Pheromones • - insect signaling chemicals • How insects communicate • These can be used to attract harmful insects to a certain area to minimize the application of pesticides

48. Plant Defenses • Plants also release volatile chemicals much like bugs do • However these chemicals have several functions • Send signals to other plants • Send signals to beneficial insects

49. Genetic Engineered Crops • For centuries plants and animals have been bred to exhibit specific traits • This took years or decades to make changes in a population

50. By inserting specific genes into plants or animals we can get a specific trait in a very short amount of time • These are transgenic organisms because they contain genes from another organism