Managing for Healthy Roots Joel Gruver School of AgricultureWestern Illinois University firstname.lastname@example.org http://www.slideshare.net/jbgruver/
The Furrow ROOTS The hidden half of agriculture
Bill Darrington (Persia, IA) Interesting example of a farmer with a root-focused management program.
How many of you regularly look at crop roots ? What do you look for?
Evidence of healthy roots extensive white color growth into the sub-soil Healthy shoot growth and good minimalproliferate in all yields evidence of directions deformities Efficient use of soil resources
Understanding corn root developmentThe seed roots stopgrowing 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.
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 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.
Is this the solution? Waiting for drier soilis the most important strategy
Sometimes it is valuable to dig a soil pit. John McGillicuddy IA crop scoutA pit will allow you to look deeper and see how the soil volume is being explored
You won’t know what is happeningunderground unless you take a look…
All you need is a shop-vac and a hose!Its just like going to the dentist!
Tillage systems affect root architecture Adapted from Hunt et al. (1986)
Long term no-till (w/ healthy soil biology) Intensive tillage Network Plow pan of bioporesOntario Ministry of Ag and Food
Ken Ferrie’s perspectiveAs the root moves through the soil it tapersdown, but when it hits a sudden densitychange, ‘it’s like a fly hit the screen. It’s too Verticaltight and it twists, bends and runs tillage toolhorizontally," said Ferrie."What causes the sudden density change? Ken Ferrie – Farm JournalCompaction. If it hits a compacted layer, it turnsand runs on top of it."Ferrie added the drastic change is caused by afarm in horizontal tillage. "You can’t use horizontaltillage without putting in a horizontal layer"Horizontal tillage creates loose soil on top and afirm shelf underneath, and the density changecreates difficulties for roots which are trying topenetrate the firmer layer.
Cotton plant’s perspective Sub-soil water and nutrients Brady and Weil (2002)
My first wading pool garden in July 2009The watermelon root system on the title slide was exhumed from this pool in Septembe
Watermelon root system exhumed from a wading pool
Wading pools filled with compost are *not* an optimal rooting environment but are an example of the plasticity of plant root systems. With limited rootingvolume but adequate water and nutrients, it is possible to grow abundant crops.
Does this look familiar? Compaction Saturated soil isprobably extends less compressibleseveral feet deep than wet soil
Prevention through improved drainage maybe the most effective strategy Artificial drainage has greatly increased the number of days when soils are suitable for deep root growth but has also contributed to many Pollution of environmental water resources problems Loss of SOM
WIU Allison Organic Research Farm – September 2007
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. Mechanism(s) of yield enhancement??
Chemical toxicitiescan inhibit root growth Aluminum toxicity Aluminum toxicity
Understanding aluminum toxicity Fe and Mn toxicities also occur at lower pHs Toxic forms of Al are bioavailable at pHs < 5.5 Aluminum toxicity is minimal above a water pH of 5.5 http://www2.ctahr.hawaii.edu/tpss/research_extension/rxsoil/alroot.gif
What damaged these corn roots? B was included in starter fertilizer
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
Both strategies are important !Feed the soil vs. Feed the crop??? Unhealthy roots use nutrients inefficiently… Healthy roots need available nutrients ! Healthy roots grow in soils with a favorable balance Acute of air, water and root soil organic matter disease Chronic root malfunction
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
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 stream H 20 Diffusion Root growth
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)
Inoculation groups for commonly grown legumesAlfalfa Group Alfalfa (Rhizobium meliloti) Black medic Bur clover Button clover White sweetclover Yellow sweetcloverClover Group Alsike clover (Rhizobium trifolii) Arrowleaf clover* Ball clover Berseem clover Crimson clover Hop clover Persian clover Red clover Rose clover* Subterranean clover* White cloverCowpea Group Alyceclover (Bradyrhizobium japonicum spp.) Cowpea Kudzu Peanut
Mycorrhizal associations Ectomycorrhizae AM endomycorrhizaeArbutoidmycorrhizae Ericoid endomycorrhizae Orchid endomycorrhizae Lavelle and Spain (2001)
Increase nutrient (P) uptake suppress pathogens Mediate plant competition Improve soil structure Glomalin Superglue of the soil ??
Tillage radish on 30” rows with oats on 7.5” rows November 2009
Radish planted on 30” rows using milo plates in mid-August 2010
It is normal for the fleshy root of cover crop radishes to rise3 or more inches out of the ground. This is not a sign of compaction!
Large scale conventional grain producersare starting to experiment with bio-strip-till. Ontario, Canada
Annual ryegrass w/crimson cloverAnnual ryegrass is a very deep rooted cover crop that has good tolerance of wet soils, combines well with other species and produces less above ground biomass than cereal rye