Fertilizer Sources: Proper Selection and Management T. Scott Murrell Northcentral Director Potash &...
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Transcript of Fertilizer Sources: Proper Selection and Management T. Scott Murrell Northcentral Director Potash &...
Fertilizer Sources: Proper Selection and Management
T. Scott MurrellNorthcentral Director
Potash & Phosphate Institute
2006
Dale F. LeikamAssociate ProfessorKansas State University
Questions to be addressed: N sources for corn
• How does corn take up and use nitrate?
• How does corn take up and use ammonium?
• Is there an optimum NH4+:NO3
- ratio?
• How do N forms react prior to plant uptake?
• How do these reactions impact phosphorus management?
Corn root: horizontal cross section
Epidermis
Root hair
Russell, 1977 Zea mays root cross-section, mature root
Cortex
Endodermis
Casparian strip
PhloemXylem Pericycle
Stele
Corn root cross section
Russell, 1977 Zea mays root cross-section, mature root
Vacuole
Cytoplasm
Cell wallPlasmodesmata
Symplasmic pathway: transport of nutrients through the cytoplasm
Marschner, 2002 Zea mays root cross-section, mature root
From rootepidermisand cortexTo xylem
Getting nutrients into the symplasmic pathway
CytoplasmVacuole
Plasmamembrane
Tonoplast
Marschner, 2002
Nitrate, phosphate, chloride:co-transport via a
proton pump
Nitrate, phosphate, chloride:co-transport via a
proton pump
H+
Anion
Cell wall
H+
Proton-ATPase pump(requires energy - ATP)
Moves H+ “uphill” againstthe electrical potential gradient andthe chemical potential gradient (pH)
ATP
pH 7.3-7.6 pH 5.5
-120 to -180 mV
Getting nutrients into the symplasmic pathway
CytoplasmVacuole
Plasmamembrane
Tonoplast
Marschner, 2002
Cations (except K)Uniport
Cations (except K)Uniport
Cell wall
Cation
Uniport:“downhill” of electrical potential gradient,
but energy is still neededto maintain the gradients
-120 to -180 mV
A comparison of ammonium and nitrate assimilation
Nitrogen form
Characteristic NO3- NH4
+
Directly stored in vacuoles? yes no
Form stored NO3- amino acids, amides
Energy costs of storage lower higher
Assimilation mechanism NO3- reduction Incorporated into
amino acids, amides
Mechanism products NH3, OH- Amino acids, amides, H+
Assimilated by roots? yes yes
Assimilated by shoots? yes no
Net C fixation by roots, (NO3-) basis 1x 5x (corn)
Marschner, 2002
Early corn growth and ammonium/nitrate ratios
5
4
3
2
1
0
Dry
wei
ght
(g p
lant
-1)
Totalconcentration
(mM)5.01.0
0.2
100 75 50 25 0 NH4+
Proportion of N formMarschner, 2002
1007550250 NO3-
Ammonium and nitrate: rhizosphere pH differences
NH4+
H+
pH
Acid
Basic
NO3-
OH-
Marschner, 2002
or HCO3-
Wheat – 2wksWheat – 2wks Corn – 8 wks oldCorn – 8 wks old
ScaleScale NO3-N NH4-N
200 kg N per ha
NO3-N NH4-N
Rōmheld
Effect of Nitrogen form on Rhizosphere pH
4.0
4.5
5.0
5.5
6.0
6.5
7.0
7.5
8.0
4.0 4.5 5.0 5.5 6.0 6.5 7.0 7.5 8.0
Bulk soil pH
Rh
izo
sph
ere
pH
NH4+ Soy NH4
+ Corn
NO3- Soy NO3
- Corn
Riley and Barber, 1971; Soon and Miller, 1977
1:1
Why is there a need for both ammonium and nitrate?
• Rhizosphere pH control
• If rhizosphere pH drops too much, ammonium uptake becomes restricted, favoring nitrate uptake
• Reverse occurs if pH increases too much from nitrate uptake
• Carbon allocation and energy regulation
• Less photosynthate is needed for nitrate assimilation
• Nitrate has lower energy storage costs since it can be stored “as is”
• So the presence of both ions helps the plant regulate rhizosphere pH, energy expenditures, and carbon allocation
Rhizosphere pH affects P uptake by corn
• 11 day old corn
• Ammonium source reduced rhizosphere pH and increased P uptake
0
1
2
3
4
5
6
3 4 5 6 7 8 9
Rhizosphere pH
To
tal P
up
tak
e, m
g P
(g
DM
)-1
Soon and Miller, 1977
Wendigo SLMCP + CaCl2MCP + Ca(NO3)2
MCP + (NH4)2SO4
Buford SiLOneida L
Starter fertilizer: NH4+ and P should be placed together
Miller and Ohlrogge, 1958
400 800 1200 1600 2000
20
40
60
0
0
20-40 lb P/acre20-40 lb P/acre + 10 lb N, mixed
20-40 lb P/acre + 10 lb N, separate
Per
cent
of
the
plan
t P
com
ing
from
the
ban
d
Phosphate added to bulk soil, lb P2O5/acre
Occurs regardlessof P soil test levelOccurs regardlessof P soil test level
Common phosphate fertilizers with ammonium
• Monoammonium phosphate (MAP)
• NH4H2PO4
• pH of 0.1M solution is 4.0
• H2PO4- ↔ HPO4
2- + H+
• Diammonium phosphate (DAP)
• (NH4)2HPO4
• pH of 0.1M solution is 7.8
• HPO42- ↔ H2PO4
- + OH-
• Ammonium polyphosphate (APP)
• pH 6.0 – 6.5
• Hydrolysis reaction
Sauchelli, 1965
Photos courtesy of Agrium
Nitrification: Converts ammonium to nitrate
Important components of the reaction:
• Requires oxygen
• Reaction is acid-forming
2NH4+ + 3O2 → 2NO2
- + 4H+
Step 1: conversion to nitrite by the Nitrosomonas bacteria
Step 2: conversion to nitrate by the Nitrobacter bacteria
2NO2- + O2 → 2NO3
-
Havlin et al., 2005 Nitrosomonas (Natl. Inst. Res. Environ.)
Reaction of anhydrous ammonia
• Reaction of ammonia with water is base-forming
• Reaction is reversible at a higher pH
• Nitrification can acidify the band that was initially higher in pH
NH3 + H2O NH4+ + OH-
Ammonia hydrolysis (splits water):
Sauchelli, 1964
Nitrification
Measured pH changes after ammonia injection
3.5 in.
< 5.1
5.1 – 6.0
6.1 – 7.0
7.1 – 8.0
> 8.0
pHscale
1 day 3 weeks 10 weeks
Cochran, 1975
Laboratory experiment:Walla Walla SiLInitial pH = 5.5CEC = 17 meq/100gN rate was equivalent to 107 lb N/acre at 20 in. spacing
Acidification patterns in soil after knifed ammonia(ridge-slot plant system)
30 in.30 in.
0
10
6.7 6.1
5.5
6.7
6.7
5.8
6.46.7
0
10
6.25.6
6.8
6.86.55.9
6.8
2 months after an early May application
14 months after an early May application
Robbins and Voss, 1989 Webster clay loamWebster clay loam
Implications of soil acidification after ammonia applications
In reduced tillage systems with knifed ammonia applications, apply in the same zones each time
• The pH increases help reverse acidity resulting from nitrification from the previous applications
• Keeps subsurface acidity from spreading to other areas
Robbins and Voss, 1989
Effects of ammonia concentration on nitrification
0
50
100
150
200
250
300
0 200 400 600 800
Ammonia (NH3-N ppm)
Nit
rate
N (
pp
m)
0
1
2
3
4
5
6
7
8
9
pH
[NO3-] after 14 days
pH after 14 days
pH right after application
Eno et al., 1955
Recommendations based on ammonia reactions
• Ammonia is the preferred source for:
• Fall applications (sustained soil temp. below 50oF)
• Spring pre-plant applications on sandy soils
• Ammonia should be injected 6-10 in. deep on friable, moist soil to avoid:
• Volatilization losses
• Injury to seedlings
Reaction of urea
• Acid-consuming
• pH will not increase above 9.3
Urea hydrolysis at pH 6.5 – 8.0
CO(NH2)2 + H+ + 2H2O → 2NH4+ + HCO3
-urease
Urea hydrolysis at pH < 6.5
CO(NH2)2 + 2H+ + 2H2O → 2NH4+ + H2CO3
Koelliker and Kissel, 1988
urease
Volatilization of ammonia
The reaction NH4 ↔ NH3 + H+ is driven by:
• Difference in NH3 activity between where the fertilizer was applied and the surrounding air (windy conditions)
• Higher pH
• Higher temperature
• Lower CEC (maintains a higher solution NH4 concentration)
• Loss of CO2, which causes the pH to increase
• Contact with crop residues, which contain urease
Koelliker and Kissel, 1988
Phosphorus form affects urea volatilization
Ammonia loss
Treatment clay, pH 5.2 silty clay loam, pH 6.0
(% of urea N)
Urea 4.7 9.8
Urea + TSP 1.8 4.9
Urea + MAP 4.2 4.1
Urea + DAP 12.8 14.2
Total N was kept constant at 117 lb N/acreP rate was kept constant at 132 lb P2O5/acre
Fan and Mackenzie, 1993
Practical suggestions for urea use
• Avoid using as a preplant application on sandy soils
• Avoid contact with the seed
• Within 2 days:
• Incorporate to a depth of 2 to 4 inches or
• Receive or apply 0.25 to 0.5 in. of precipitation
• Other considerations for no-till
• Consider surface bands to reduce contact with urease
• If also applying P, band MAP or TSP with the urea at the surface
Summary
• N nutrition affects the pH of the soil surrounding the root and P uptake. Ammonium forms should be placed with P.
• When ammonia is formed, nitrification can be delayed
• In reduced tillage systems, acidification from nitrification needs to be controlled, possibly through the use of N fertilizers that are initially base-forming, repetitively banded in the same location
• Phosphorus can be a good product to co-apply with ammonium banded near the seed
• Phosphorus can be a good product to co-apply with urea banded at the surface
References
Anghinoni, I. and S.A. Barber. 1980b. Predicting the most efficient phosphorus placement for corn. Soil Sci. Soc. Am. J. 44:1016-1020.
Barber, S.A. 1984. Soil nutrient bioavailability: A mechanistic approach. Wiley Interscience, New York, NY.
Barber, S.A. 1978. Growth and nutrient uptake of soybean roots under field conditions. Agron. J. 70:457-461.
Cochran, V.L., F.E. Koehler, and R.I. Papendick. 1975. Straw placement: Its effect on nitrification of anhydrous ammonia. Agron. J. 67:537-540.
Edwards, J.H. and S.A. Barber. 1976. Phosphorus uptake rate of soybean roots as influenced by plant age, root trimming, and solution P concentration. Agron. J. 68:973-975.
Eno, C.F., W.G. Blue, and J.M. Good, Jr. 1955. The effect of anhydrous ammonia on nematodes, fungi, bacteria, and nitrification in some Florida soils. Agron. J. 19:55-58.
Fan, M.X. and A.F. Mackenzie. 1993. Urea and phosphate interactions in fertilizer microsites: Ammonia volatilization and pH changes. Soil Sci. Soc. Am. J. 57:839-845.
Havlin, J.L., J.D. Beaton, S.L. Tisdale, and W.L. Nelson. 2005. Soil fertility and fertilizers: An introduction to nutrient management. 7th ed. Pearson Prentice Hall, Upper Saddle River, NJ.
Koelliker, J.K. and D.E. Kissel. 1988. Chemical equilibria affecting ammonia volatilization. p.37-52. In B.R. Bock and D.E. Kissel (ed.) Ammonia volatilization from urea fertilizers. Bull. Y-206. Natl. Fert. Development Center, TVA, Muscle Shoals, AL.
Marschner, H.M. 2002. Mineral nutrition of higher plants. 2nd ed. Academic Press, New York, NY.
Mengel, D.B. and S.A. Barber. 1974. Rate of nutrient uptake per unit of corn root under field conditions. Agron. J. 66:399-402. Borkert, C.M. and S.A. Barber. 1985b. Predicting the most efficient phosphorus placement for soybeans. Soil Sci. Soc. Am. J. 49:901-904.
Miller, H.H. and A.J. Ohlrogge. 1958. Principles of nutrient uptake from fertilizer bands. I. Effect of placement of nitrogen fertilizer on the uptake of band-placed phosphorus at different soil phosphorus levels. Agron. J. 50:95-97.
Riley, D. and S.A. Barber. 1971. Effect of ammonium and nitrate fertilization on phosphorus uptake as related to root-induced pH changes at the root-soil interface. Soil Sci. Soc. Am. Proc. 35:301-306.
Robbins, S.G. and R.D. Voss. 1989. Acidic zones from ammonia application in conservation tillage systems. Soil Sci. Soc. Am. J. 53:1256-1263.
Russell, R.S. 1977. Plant root systems: Their function and interaction with the soil. McGraw-Hill, New York, NY.
Sauchelli, V. 1965. Phosphates in agriculture. Reinhold Publishing Co., New York, NY.
Sauchelli, V. 1964. Nitrogen: Chemical and physical properties. p.10-17. In V. Sauchelli (ed.) Fertilizer nitrogen: It’s chemistry and technology. ACS Monograph Ser. 161. Reinhold Publishing Co., New York, NY.
Soon, Y.K. and M.H. Miller. 1977. Changes in the rhizosphere due to NH4+ and NO3- fertilization and phosphorus uptake by corn seedlings (Zea mays L.). Soil Sci. Soc. Am. J. 41:77-80.
Maturationzone
Elongationzone
MeristematiczoneRoot cap
cells ahead of theapical meristem
Mucigel
Xylemtransports ions and
water to otherareas in the plant
Phloemtransports products of
photosynthesis to the roots
EndodermisEncases the stele
and acts as a barrier
Corn root: longitudinal cross section
Nutrient influx by roots
• Ions are not simply absorbed according to their ratios in solution
• Ions with this characteristic influx pattern require energy to be absorbed
• H2PO4-, HPO4
2-, NO3-
• K+, NH4+
• Maximum influx is reached at higher solution concentrations (Imax)
22-23 day old soybean roots22-23 day old soybean roots
Barber, 1984; Edwards and Barber, 1976
-0.5
0.0
0.5
1.0
1.5
2.0
2.5
3.0
0 1 2 3 4 5
Solution P, 10-6 lb P2O5/gal
Infl
ux,
10-1
4 lb
P2O
5 /
(in
s)
Imax
Fertilized soil fraction (%)
20 40 60 80 1000
Rel
ativ
e dr
y m
atte
r yi
eld
(%)
25
50
75
100
0
Corn
Soybean
10-3 lb P2O5 per pot
3.6
0.9
Anghinoni and Barber, 1980; Borkert and Barber, 1985b
P influx varies with plant age: The case for starter
-1
0
1
2
3
4
5
0 20 40 60 80 100 120
Plant age, days
Infl
ux,
10-5
lb
P2O
5 /
(in
. d
ay)
Corn
Soybean
Barber, 1978; Mengel and Barber, 1974
Corn can take in Pat a high rate early
(per unit of root)but not later
Corn can take in Pat a high rate early
(per unit of root)but not later