How many of you regularly look at crop roots ? John McGillicuddy IA crop scout
Bill Darrington (Persia, IA)One of several readings for this week
Read the attached article and submit answers using WO before the start of classnext Wednesday.1)Describe several factors contributing to deep root growth on Bill Darringtonsfarm.2) The article refers to Ray Rawson as the guru of "vertical farming"... what is"vertical farming" and what did Bill Darrington learn from Ray Rawson about soilaeration?3) Why does Bill Darrington dig so many soil pits and what does he look for?4) What is Bill Darringtons perspective on anhydrous ammonia? Do you agreewith this perspective?5) Have you ever looked at roots in a soil pit? If so, describe something youobserved. If not, when do you think you will have an opportunity to look at someroots? What do you think you will see?
All you need to do to grow healthy roots is use rootworm resistant genetics… right??When rootworm pressure is high, rootworm resistant genetics normally result in much healthier roots
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
We have witnessed the historically low densities of European corn borers across Illinois and some nearbystates that are now believed to be linked to the widespread adoption of Bt corn hybrids. Will we see a similar phenomenon unfold with western corn rootworms? I suspect we might be headed down this road. Will westerncorn rootworms adapt as they have repeatedly done so in the past? If we dont integrate management tactics, we could have the answer sooner than we would like.
Early MayWarmer and drier than soilwith other cover crops and almost no weed growth
Visual evidence of biodrillingCanola rootRapeseed root
The experiment was planted to corn on May 29 2008 Corn following radishestablished well, had the lowest in-row weed pressure and yielded about 10 bu more.
Chemical toxicitiescan inhibit root growth Aluminum toxicity Aluminum toxicity
Galled root system of tomato infected with root-knot nematode, Meloidogyne sp., compared with non- infected root system Root pathogens can inhibit root growth http://www.agnr.umd.edu/users/nrsl/entm/nematology/images/eis143.jpg
Absorptive network for limiting soil resourcesof water and nutrientsMechanical structures that support plants,strengthen soil, construct channels, breakrocks, etc.Hydraulic conduits that redistribute soil waterand nutrientsHabitats for mycorrhizal fungi, rhizosphereand rhizoplane organisms
Carbon pumps that feed soil organisms and contribute to soil organic matter Storage organsChemical factories that may change soil pH, poison competitors, filter out toxins, concentrate rare elements, etc.A sensor network that helps regulate plant growth
The cell wall of the endodermis (pink inner strip of cells) is waterproofed by theCasparian strip, which forces water to enter the symplast before it can enter theroot xylem phloem root hair xylemepidermis endodermis cortex
Apoplast vs. symplastThe movement of fluids from the root hairs to the xylemcan occur through one of two conductive pathways–the apoplast and the symplast.The apoplast route consists of inter-cellular spaceswithin the root cortex along which water and solutescan diffuse.The symplast route consists of channels through cellsalong which water and solutes are actively transported.
Water moves upwardthrough plantswhenever there is aprogressively morenegative gradient ofwater potential alongthe soil-plant-atmospherecontinuum
H20A continuous Solar energychain of water drives the molecules is process pulled up through the Plants provide plant the conduit H20 H20 H20
Understanding nutrient uptake H20 Root exudatesN, S, P activate soil microbes Transpirational Root growth stream H 20 Diffusion
Nutrient uptake is an active and selective process outside cell inside cell
Rhizosphere Roots normally occupy < 1% of topsoil volumeThe rhizophere isnormally < 10 % of soilvolume Zone of root influence
Navigating the rhizosphere End of the Rhizoplane rhizosphere Endo- Rhizosphere Ecto-RhizosphereMicrobial activity > 90% < 10% of soil volume of soil volume A few millimeters (Lavelle and Spain, 2001)
Both strategies are important !Feed the soil vs. Feed the crop??? Unhealthy roots use nutrients inefficiently… Healthy roots need available nutrients ! Acute root disease Chronic root malfunction
How do you know if a crop has healthy roots? extend into the white color B horizonproliferate in all minimal directions evidence of deformities
Inoculation groups for commonly grown legumes Alfalfa Group Alfalfa (Rhizobium meliloti) Black medic Bur clover Button clover White sweetclover Yellow sweetclover Clover Group Alsike clover (Rhizobium trifolii) Arrowleaf clover* Ball clover Berseem clover Crimson clover Hop clover Persian clover Red clover Rose clover* Subterranean clover* White clover Cowpea Group AlycecloverSoybean has its own inoculation group!! (Bradyrhizobium japonicum spp.) Cowpea Kudzu Peanut
Mycorrhizal associations Ectomycorrhizae AM endomycorrhizaeArbutoidmycorrhizae Ericoid endomycorrhizae Orchid endomycorrhizae Lavelle and Spain (2001)
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
Increase nutrient (P) uptake suppress pathogens Mediate plant competition Improve soil structure Glomalin Superglue of the soil ??