fall application of fertilizer

8/13/2019 Fall Application of Fertilizer

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2/19

This topic was requested in the 2012 OKNo-till Survey.

Fall applied fertilizer.

They do it up north Why or Why not in Ok.

Will focus on Summer Crops, but applies

to wheat and Canola Consider their growth pattern.


3/19

For Summer Crops Practice of applying

NH3 in fall with

nitrification inhib. It is all about the

temp.

State Average WinterTemp F

Iowa 21.7

Illinois 28.3

Indiana 29.4Kansas 31.9

Missouri 32

Michigan 21.7

Minnesota 16

Nebraska 25.7

Ohio 29

Oklahoma 39


4/19

Add the potential for a wet winter.

Area of the State 100yrAverage WinterPrecip in Inches

Range in Precipsince 1980

North East 5.6 16 2

North Central 3.2 8 1

West Central 2.9 8 1

Central 4.5 14 1

South West 3.5 9 1


5/19


6/19

Urea, Ammonia, Ammonium, Nitrate Urea Converts rapidly to NH3

NH3 in presence of moisture Immediately NH4.

NH4 converted to NO3 via Nitrification.

NO3 will move with soil solution


7/19

Microbial Process Nitrosomonas

Nitrobactor

Therefore Driven byTemperature and Moisture

Up north frozen soil + Nitrificationinhibitor = Acceptable practice Not Ideal


8/19

Not Subject to the same losses asNitrogen.

So not as bad of an idea.

But Soil pH and Ca level will impact this.


9/19

Most soluble, (monocalcium phosphate) reverts tothe most insoluble (apatite). Reversion is expected to take considerable time,

primarily because the concentration of reactants isrelatively low.

Even though the common fertilizer monocalciumphosphate (0-46-0) will gradually become lesssoluble forms of calcium phosphates, the transitionis slow enough that concentrations of availablephosphate (H2PO4- and HPO42-) in the soil will be

sufficiently high throughout the season to benefitthe crop. Usually a year after fertilization the transition to

highly insoluble forms is almost complete and thereis little residual effect of the past years application.


10/19

Availability of applied? Most available form is Mono Calcium

Phosphate.

TSP, DAP, MAP, APPThe mostavailable these will EVERbe in

the day they are first, dissolved orapplied.


11/19

Orthophosphate P

0.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

0.80

0.90

1.00

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14

Solution pH

MolefractonP H PO H PO

-HPO

2-PO

3-

H PO -

Ionic forms of P taken up by plants (H2PO4- and HPO42) exist in equalamounts at about pH 7.2. Plants do not appear to have a preference for

one form over the other, thus there is little justification for trying to lime a soilto a pH where P is most available.


12/19


13/19

SWFAL 3369

Samples

10%


14/19

Total K in soils averages about 40,000 lb/acre

Soil potassium is present in four categoricalforms

occluded (within soil minerals such as feldspar,mica, etc), 98% of total

fixed (trapped within the lattice of 2:1 expandingclay minerals), 1% of total

exchangeable. 1% of total (100-1000ppm)

solution, 0.1% of total (1-10 ppm)


15/19

Soil K

K+K+ K+ K+ K+ = K+ K+ K+ K+ = K+ = K+

K+

Mineral weathering =====

feldspar, mica (occluded)hydrous micas (fixed) clays(exchangeable)=solution

Available K. Solution and exchangeable K normallyrepresent "available" K for plants during a growingseason


16/19

Plant uptake is by diffusion (90%) and mass flow

(10%) K is immobile in soil (on a scale of 1 to 100, with 100 being

most mobile, NO3- is 99, K+ is 33, and HPO42- is 1)

Factors affecting amount of available K to plants

soil mineralogy and climate CEC

clay and organic matter content

K fixation and/or release

wetting and drying freezing and thawing

subsoil and rooting depth

soil pH

competing exchangeable ions


17/19

Brian Arnall

373 Ag Hall405-744-1722

[email protected]

Presentation available @www.npk.okstate.edu

Twitter: @OSU_NPK

YouTube Channel: OSUNPK

www.extensionnews.okstate.edu


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fall application of fertilizer

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