The hidden half of agriculture

1. The hidden half of agriculture

2. How many of you regularly look at crop roots ? John McGillicuddy

3. Bill Darrington (Persia, IA)

4. All you need to do is use rootworm resistant genetics… right?? When rootworm pressure is high, rootworm resistant genetics normally result in much healthier roots

5. Rootworm resistant genetics are not a silver bullet ! Severe damage by corn rootworm larvae to roots of a biotech corn rootworm hybrid http://www.ipm.iastate.edu/ipm/icm/2006/11-13/btcorn.html

6. Seminal roots cease new growth shortly after the coleoptile emerges from the soil surface. The nodal root system becomes visible at ~ V1. The nodal root system becomes the dominant system by V6.

7. 16 weeks 4 weeks 8 weeks 7 feet deep !!

8. 1926

9. ?

10. PLOW PAN Compacted layers can severely limit root growth Sub-soil water and nutrients Brady and Weil (2002) Brady and Weil (2002)

11. Adapted from Hunt et al. (1986)

12. Long term no-till (w/ healthy soil biology) Intensive tillage Network of biopores Plow pan Ontario Ministry of Ag and Food

13. Which solution would you use ?

14. WIU Allison Organic Research Farm – September 2007

16. Please plant me no-till next spring !! January

17. Visual evidence of biodrilling Canola root Rapeseed root

18. The experiment was planted to corn on May 29 2008 Corn following radish established well and had the lowest weed pressure in the row. Maybe you should come out to the farm and see how things look this fall…

19. Chemical toxicities can inhibit root growth Aluminum toxicity Aluminum toxicity

20. Galled root system of tomato infected with root-knot nematode, Meloidogyne sp., compared with non-infected root system Root pathogens can inhibit root growth Root knot juvenile penetrating a tomato root http://www.agnr.umd.edu/users/nrsl/entm/nematology/images/eis143.jpg

21. You won’t know what is happening underground unless you take a look…

22. Roots have many functions !

23. Absorptive network for limiting soil resources of water and nutrients • Mechanical structures that support plants, strengthen soil, construct channels, break rocks, etc. • Hydraulic conduits that redistribute soil water and nutrients • Habitats for mycorrhizal fungi, rhizosphere and rhizoplane organisms

24. Carbon pumps that feed soil organisms and contribute to soil organic matter • Storage organs • Chemical factories that may change soil pH, poison competitors, filter out toxins, concentrate rare elements, etc. • A sensor network that helps regulate plant growth

25. http://www.sparknotes.com/biology/plants/plantstructures/section2.rhtmlhttp://www.sparknotes.com/biology/plants/plantstructures/section2.rhtml

28. http://www.sparknotes.com/biology/plants/plantstructures/section2.rhtmlhttp://www.sparknotes.com/biology/plants/plantstructures/section2.rhtml

29. The movement of fluids from the root hairs to the xylem can occur through one of two conductive pathways– the apoplast and the symplast. The apoplast route consists of inter-cellular spaces within the root cortex along which water and solutes can diffuse. The symplast route consists of channels through cells along which water and solutes are actively transported.

30. The cell wall of the endodermis (pink inner strip of cells) is waterproofed by the suberised Casparian strip, which forces water to enter the symplast before it can enter the root xylem

31. http://www.mie.utoronto.ca/labs/lcdlab/biopic/fig/35.03.jpg

32. Water moves upward through plants whenever there is a progressively more negative gradient of water potential along the soil-plant-atmosphere continuum

33. H20 A continuous chain of water molecules is pulled up through the plant Solar energy drives the process Plants provide the conduit H20 H20 H20

34. Understanding nutrient uptake H20 N, S, P Transpirational stream Root exudates activate soil microbes H20 Root growth Diffusion

35. Nutrient uptake is an active and selective process

36. Rhizosphere Roots normally occupy < 1% of topsoil volume The rhizophere is normally < 10 % of soil volume Zone of root influence

37. Navigating the rhizosphere End of the rhizosphere Rhizoplane Endo-Rhizosphere Ecto-Rhizosphere > 90% of soil volume < 10% of soil volume Microbial activity A few millimeters (Lavelle and Spain, 2001)

38. Feed the soil vs. Feed the crop Both strategies are important ! Healthy roots need available nutrients ! Unhealthy roots use nutrients inefficiently… Acute root disease Chronic root malfunction

40. Healthy cowpea nodule with a pink interior

41. Mycorrhizal associations Ectomycorrhizae AM endomycorrhizae Arbutoid mycorrhizae Ericoid endomycorrhizae Orchid endomycorrhizae Lavelle and Spain (2001)

42. Mycorrhizal Networks: Connecting plants intra- and interspecifically • Many plants are connected underground by mycorrhizal hyphal interconnections. • Mycorrhizal (AM) fungi are not host specific. Illustration by Mark Brundrett

43. Ectomycorrhizal roots

44. Close up of ecto-mycorrhiza

45. Increase nutrient (P) uptake suppress pathogens Mediate plant competition Improve soil structure Glomalin Superglue of the soil ??

46. Roots are worth a closer look !