nutrientsmart - guelph, ontario january 2018
TRANSCRIPT
Soil Fertility 101?
Ray Weil
NutrientSmart - Guelph, Ontario January 2018
Guiding principles of soil fertility management
• Soils are complex, integrated systems.
• Soils are alive! C drives the food web.
• Soils are 3-D – use the whole profile.
• Each nutrient has its cycle – fertilizer can supplement, not supplant.
• Economic and environmental optima often allow a win – win.
• Lots of dollars still going down the drain.
Soil
Chemistry
Soil
Physics
Soil
Biology
Plant root
physiology
Soil types
formation
Landscape,
ecology
Soils are complex, integrated
systems.
.
Plant root
physiology
Rhizosphere
soil sheathsWashed roots
Mucigel
Root cap
cells
spilling C
Roothairs
Soils are alive –
roots are part of a
community
Crop rootsSoil Pests
Beneficial
nematodes
Beneficial
bacteria
Mycorrhizal
partners
Crop roots
Use the full
profile
Soils are three-dimensional
Which nutrient & water
reservoir do you want supporting your crops?
Calcium-
phosphates
Iron, Aluminum
-phosphates
Organic-
phosphorus
P in
Solution
2023
0.1
0.2
0.3
P fluxes
for 106
Ohio
fields, Kg
P/ha
Each
nutrient has
its soil cycle
Forms of water-soluble phosphorus
From Weil & Brady (20017) using means for 14 unfertilized pastures on alluvial Vermont Inceptisols in Young et al. (2013)]
News Flash! It’s not all orthophosphate
(H2PO4).
Six basic strategies that plant roots
may employ to enhance their uptake of
various forms of phosphorus from soils.
Increased root
absorptive
surface area
Chelate iron
or aluminum to
release P.
Dissolve Ca–P compounds
with acid exudates
Exude
phosphatase
enzymes to
release
P from organic
compounds
Exude substances
to stimulate
P-solubilizing
rhizobacteria.
Encourage
colonization by
mycorrhizal fungi that
help plants take up P
Six plant
strategies to
enhance P
availability
Root-Fungi alliance (Mycorrhizae) is a game changer for plants.
Sawyer, J.E., and A.P. Mallarino. 1999. Differentiating and understanding the Mehlich
3, Bray, and Olsen soil phosphorus tests. 19th Annual Crop Pest Management Short
Course, University of Minnesota.
Best case correlation data for two common P soil tests
3.0
2.5
2.0
1.5
1.0
0.5
0.0
Dra
inag
e w
ate
r P, m
g / L
Total P Concentration
In Drainage WaterBroadbalk Experiment, England
0 10 20 30 40 50 60 70 80 90 100 110Olsen soil test P, mg/kg
From: Heckrath etal 1995
Agro
nom
icoptim
um
Nutrient Input-Output Balance on a Farm
Manure/Compost
Fertilizer
N fixation
Deposition
Feed: grain,
hay, salts
Bedding
Sales: crops,
animals, milk
Manure sales
Leaching
NOx losses
NH3 volatilization
Runoff
Erosion
Fast etal. 2009. Better Crops/Vol. 93 (No. 1)
Phosphorus buildup ‘sins’
of our grandfathers
Annual Total P Loading to Lake Erie
Lake Erie Algal Bloom,
Ohio soil photos:
Darrell Norton
Ca2+ & ionic Strength Reduce Dispersion
Gypsum
applied
to soil
surface
No
Gypsum
Before rain
Gypsum on surface
No tillGypsum Turbo-
tilled into soil
During rain
•Preferential
flow
•Bypass flow
•Macro-pore
flow
Hi -P
Lo -P
Water
Ca2+ precipitates soluble P
Cover crops can …
1. solubilize P
2. bring P to surface
P
J N Galloway et al. Science 2008;320:889-892
Internationally Traded
N(A) fertilizer (31 Tg N),
(B) grain (12 Tg N),
(C) meat (0.8 Tg N).
North America: ~ 6500 Tg N imported as fertilizer ~ 4500 Tg N exported as grain
Yield (kg N ha-1 yr-1)
N U
se E
ffic
ien
cy (
har
vest
ed /
app
lied
)
Zhang et al. 2015.
Goal: high NUE and YieldsWhere
we want to be.
Economists’ quadratic “model”:Y= a+bX+cX2
Interpretation of field responses to make nutrient application recommendations
Corn Crop Response to N Fertilizer
From Cerrato and Blackmer, 1990.
Recommended
optimum = 220
kg/ha
Y= a+bX=cX2
200 lbs N/ 158 bu~ 1.25 lbs N/ bu of yield
Recommended
optimum =
110 kg/ha
Corn Crop Response to N Fertilizer
105 lbs N/ 158 bu~ 0.65 lbs N/ bu of yield
On average, Maryland farmers are ahead of
other regions in nitrogen management
• Using less fertilizer with manadatory nutrient
management plans (1.2 0.8-0.9 lb N/bu
expected yield)
• Split applications of N
• Soil N tests (PSNT)
• Adapt-N and other
computer models to
predict N needs.
https://plantsciences.missouri.edu/nutrientmanagement/nitrogen/images/practices_figure2.jpg
Nitrogen Use and Corn Yield Trends in Maryland
https://stock-clip.com/video-footage/hand+squeeze+orange+juice+in+a+glass
Good
start…
https://www.pinterest.com/pin/549017010801557308/
Next
level…
5 ft2 corn rows
apart
Barley cover crop responding at Thanksgivingto UAN side-dressed to corn previous June
?
But Maryland, too, still has a “leaky” N system
Leftover N from June side-dressing being used by rye cover crop in Nov.
1
2 3
4
Veihmeyer, F.J. 1929. An improved soil sampling tube. Soil Science 27:147-152.
1 ft
2 ft
2 ft
2 ft
1 ft
2 ft
2 ft
2 ft
Transect of 8-10 cores per farm
0-15
15-30
30-45
45-60
60-75
75-90
90-105
105-120
120-135
135-150
150-165
165-180
180-195
195-210
Depth
, cm
0 5 10 15 20 25 30 35 40 45 50
Ammonium-N, kg/ha
SoybeanCorn
Crop
0-15
15-30
30-45
45-60
60-75
75-90
90-105
105-120
120-135
135-150
150-165
165-180
180-195
195-210
Depth
, cm
0 5 10 15 20 25 30 35 40 45 50
Nitrate-N, kg/ha
SoybeanCorn
Crop
*
*
*
*
*
*
*
*
*
NO3--NNH4
+-N
Means of 20 profiles. Paired side-by-side soybean & cornfields on 4 farms in PG, Howard and Kent Counties. Fall 2016.
Kg N /ha in each 15 cm layer
EARLY planting is essential for fall
cover crop activityAugust
1m
2m
0m
Nov 2015
Soil nitrate
NO3-N (kg/ha)
Dep
th (
cm)
Dep
th (
cm)
Apr 2016
ab
ab
ab
ab
ab
ab
ab
ab ab
ab ab
ab ab
ab a
ab ab
NO3-N (kg/ha)
Letter indicates sig different NO3-N in layer (p < 0.05, unless noted)
(0.08)
(0.09)
Field Suction Lysimeters Sample Soil Pore Water 4 ft Deep
• Data collected from February -April
• 3 replications 60’ x 300’ plots• Covers planted 15 Sept.1. No cover2. Sole rye3. Sole radish4. Triticale, radish, & clover
mixture5. Triticale, radish, & clover
mixture, planted two weeks later
Even cover crop frost-killed in December impacted pore-water nitrate at 100 cm deep in February-March-April
Nitrate in sandy soil pore water, 90 cm deep on 22 Feb. 2017
Triticale-clover-radish mix planted 15 Aug – 30 Sept
EPA Std
Down the drain? Changes (1960 to 2010) in pH & potassium concentrations in rivers across the US.
PotassiumIn rivers
Kaushal, et al. 2018. Freshwater salinization syndrome on a continental scale. Proc. Natl Acad. of Sciences.
KFertilizer
?
https://www.no-tillfarmer.com/articles/4664-reasons-to-no-till-plant-into-green-cover-crops
Keys to effective nutrient mgtwith cover crops:
• Plant early—get deep roots in Fall
• Include brassica + legume + grass
• Kill late—let covers work for you in Spring
• Soils are integrated systems.
• Soils are alive!
• Soils are deep.
• Each nutrient has its cycle
• Fertilizer can supplement, not supplant.
• Economic and environmental win-win.
• Lots of dollars still going down the drain.
Lots to think about…
Thanks for your attention.
And remember:• Start where you are. • Use what you have. • Do what you can.
- Arthur Ashe