Phosphorus Nutrition of Alfalfa. Phosphorus (P) Nutrition of Alfalfa U.S. alfalfa hay yields keep...
Transcript of Phosphorus Nutrition of Alfalfa. Phosphorus (P) Nutrition of Alfalfa U.S. alfalfa hay yields keep...
Phosphorus Nutritionof Alfalfa
Phosphorus (P) Nutritionof Alfalfa
• U.S. alfalfa hay yields keep increasing
• Nutrient uptake and removal
• Alfalfa root development
• General P nutrition
• P boosts hay yield, recovery, and quality
• P inputs: frequency and source
• Requirement for balanced nutrition
Outline:
U.S. Alfalfa Hay Yields…An Upward Trend
Year
Source: USDA-NASS
2
2.5
3
3.5
4
1970 1975 1980 1985 1990 1995 2000
Yie
ld,
ton
/A
Record Yield:Researchers at University of Arizona(Yuma) set record for alfalfa yieldin a year:24.1 tons/A alfalfa hay in10 cuttings
• Optimal and uniform irrigation• Chopped hay removed immediately after cutting• N fertilizer regularly added – was it needed?
• 460 lb P2O5/A added before planting
• K management unknown
• 1,440 lb K2O and 360 lb P2O5/A removed in hay
Ludwick, 2000; Arizona
Alfalfa Nutrient Uptakeand Removal
• Alfalfa has higher demandfor nutrients than most crops
NutrientAmount
Removed
lb/ton
P2O5 15
K2O 60
Ca 30
Mg 6
S 6
N (through fixation) 60
Alfalfa Root Development
• Most lateral roots are near the soil surface for the first year, but more deep lateral roots develop as the plant ages
• Alfalfa has lower root density than many grasses and a deeper rooting zone
• P and K application increase root growth, enabling roots to obtain moisture and nutrients from greater volume of soil
Available P
Unavailable P
Phosphorus in Soils
• Total P in many soils (0 to 6 in.) ranges from 400 to 2,000 lb/A…but only a fraction of that is available for plant uptake each season
The primary cause of low, short-term uptakeof P fertilizer:• The inability of P to move
to absorbing roots
Pla
nt r
oot
Higher Pconcentration
Lower Pconcentration
Diff
usio
n
Adequate P is essential for strong root systemsHigher levels of nutrients are needed to support vigorous
plant growth in cool soil conditions
Temperature Effect on Nutrient Uptake
Cool soil temperatures will:
• slow nutrient release from soil organic matter
• reduce diffusion of nutrients to the roots
• hinder root absorption and translocation
P Functions in Plants
• Energy storage and transfer– Phosphate compounds are “energy currency”
– (such as ADP and ATP)
• Structural component of biochemicals– Seed formation
– Calcium and magnesium phytate
• Maintenance and transfer of genetic code
• Root growth, rapid crop establishment
• Early maturity, quicker recovery
P Fertilization Increases Nodulation
Azcon et al., 1988
0
50
100
150
200
250
300
75% 90% 100%
4.510.315.621.8
Soil P, ppm
Nu
mb
er o
f n
od
ule
s
Soil water holding capacity
P Fertilization Increases Nodule Growth
Gates, 1974
0 64126
254
510
0
100
200
300
400
500
600
P application, lb P2O5/A
Nod
ule
dry
wei
ght,
mg/
plan
t
P Improves Alfalfa Growth and Recovery
Li et al., 1998
Alfalfa regrows faster aftercutting with adequate P
0
20
40
60
80
100
120
0 7 14 21 28
Days after cutting
Sh
oo
t w
eig
ht,
mg
/pla
nt
P conc., mmol
0126
Alfalfa develops more shoots after cutting with adequate P
0
1
2
3
4
5
0 7 14 21 28
Days after cutting
Sh
oo
ts/p
lan
t
P conc., mmol
0126
P Response: Timing and Application Study
• Six-year study initiated to evaluate effect of P timing and application method
• Broadcast or banded P fertilizer
• Frequency: – 100 lb P2O5/A every year
– 200 lb P2O5/A every 2 years
– 600 lb P2O5/A in a one-time preplant application
• Total 6-year P rate was the same for all treatments: variables were timing and placement
Mullen et al., 2000; OK
Yield Response to P inYears One and Six
Knifed-in 6 in. deepP application, lb P2O5/A and frequency
0
10
20
30
100/yr 200/2 yr 600/6 yr 200/2 yr 600/6 yr
Year 1 Year 6
Alf
alf
a y
ield
res
po
nse
, %
in
crea
se
abo
ve c
hec
k
Mullen et al., 2000; OK
Yield Response:Method and Timing
P Application, lb P2O5/A and frequency
Knifed-in 6 in. deep
Cumulative Yield Response
3.4
4.24.7
5.8
6.8
0
1
2
3
4
5
6
7
100 lbs/A/yr 200 lbs/A/2-yr 600 lbs/A/6-yr 200 lbs/A/2-yr 600 lbs/A/6-yr
To
tal y
ield
incr
ease
, to
n/A
Mullen et al., 2000; OK
Increase in Alfalfa GrowthDue to P Fertilization(split over 5 years or one-time application)
Broadcast application
Ave
rag
e an
nu
alyi
eld
in
crea
se,
lb/A
P application, lb P2O5/A
0
1000
2000
3000
4000
5000
6000
100 200 300 400
5-yr splitapplication
One-timeapplication
Mullen et al., 2000; OK
Increase in Alfalfa GrowthDue to P Fertilization(split over 5 years or one-time application)
P application, lb P2O5/A
0
1000
2000
3000
4000
5000
6000
100 200 300 400
5-yr split Papplication
One-time Papplication
Disc-band application
Ave
rag
e an
nu
alyi
eld
in
crea
se,
lb/A
Mullen et al., 2000; Alberta
Influence of P Application on Increasing Alfalfa Yield (one-time application or annual application)
0
1000
2000
3000
4000
5000
6000
Yea
r 1
Yea
r 2
Yea
r 3
Yea
r 4
Yea
r 5
5-yr
Avg
Annual Papplication
One-time Papplication
Broadcast application
Ave
rag
e an
nu
alyi
eld
in
crea
se,
lb/A
Mullen et al., 2000; Alberta
Influence of P Application on Increasing Alfalfa Yield (one-time application or annual application)
0
1000
2000
3000
4000
5000
6000
7000
Year 1
Year 2
Year 3
Year 4
Year 5
5-y
r A
vg
Annual Papplication
One-time Papplication
Disc-band application
Ave
rag
e an
nu
alyi
eld
in
crea
se,
lb/A
Mullen et al., 2000; Alberta
James, 1995; Utah
• Yield response to added P most evident at first cutting
• Soil P fertility was maintained by small annual applications or a large one-time application
Alfalfa Response toAdded P Fertilizer
P application rate, lb P2O5/A
0 225 450
Cut 3
Cut 2
Cut 1
(STP=8 ppm, 0-45-0)
To
tal 3
-yea
r yi
eld
, to
n
Established StandsOften Need Additional P
• Soil testing and tissueanalysis can revealneed for fertilization.
• P fertilizer does not movefar in soil:
– Soil incorporationprior to planting is best
– Top-dressed and irrigated P is suitablefor subsequent fertilization
• P moves during freeze/thaw cycles, washes into soil cracks, and is taken up by shallow surface roots and crowns and becomes available for plant uptake.
Ottman et al., 2001; AZ
What P Source Is Superiorfor Alfalfa?
• Three-year study with 24 cuttings:– 10-34-0 applied in irrigation water
– 10-34-0 sprayed on soil surface
– 11-52-0 granules broadcast applied • (0, 20,40, 60, 100 lb P2O5/A/yr for 3 years)
• Positive hay yield response to P, but:– No differences in P sources or methods
of application in yield or tissueP concentration
Koenig, 2003; Utah
P Source? Not a Significant Factor for Alfalfa Yields
• Four P sources compared(2 liquid, 2 solid):
– Yield response to P fertilization(11 to 27% increase) under irrigation
No differences in P fertilizersources
• Placement compared:– Surface banding or broadcast on
established alfalfa stands
No yield differences due tofertilizer placement
Cihacek, 1993; NM
0
2
4
6
8
10
12
14
Check MAP DAP APP
Treatment
So
il T
est
P,
pp
m
Initial198219831984
(annual application, 115 lb P2O5/acre)
7 ppm critical value
Effect of P Fertilizeron Soil P Concentrations
• Failure to replace harvested nutrients will gradually deplete soil nutrient supply and reduce yields
Prior to planting:
• Incorporate P forestablishment of strongroot systems, promotingrapid recovery, andmaintaining healthy stands
• Provide balanced nutrition:Adequate K, Ca, Mg, S, B, etc.
• Eliminate soil pH problems - alfalfa does not thrive in acid soils
Low P
AdequateP
Preparing the Soil Before Planting Is Key
0
3
6
9
Year 1 Year 2 Year 3
No P or K
K only
P only
P and K
Alf
alfa
hay
yie
ld, t
on
/A/y
r
Berg et al., 2005; IN
Balanced P and K NutritionIs Essential for OptimalYields and Stand Maintenance
Proper Attention to All Nutrients Is Required for Healthy Plants and High Yield Levels
Berg et al., 2005; IN
General Guidelines for P Fertilization
• Use soil testing to guide P fertilization decisions and use local recommendations for best results
• Incorporate adequate P into the top 2 to 6 in. of soil prior to planting to meet the first years of productionand nutrient removal in harvested hay
• Use tissue analysis to determine need for subsequent-year phosphate
• Application can be made any time of the year-- frequently during winter months to meet the high-demand period in the Spring
– (avoiding application to snow-covered, frozen, or saturated fields with the potential risk of runoff)
Diagnosis of P Deficiencies
• Visual Observation:– Distinct P deficiencies are seldom observable
on alfalfa – not an effective diagnostic method!
• Soil Testing– Soil test prior to planting and regularly afterwards
• Tissue Analysis– Best way to monitor plant performance and
prevent hidden hunger and yield loss
• Recommended tissue concentration:– 0.25 to 0.40% P in top third of plant
Both P Fertilizer and Animal Manure Provide Nutrition for Alfalfa
Goss & Stewart, 1979; Texas
Cu
mu
lati
ve a
lfal
fa y
ield
, g/p
ot
Manure Management
• Manure supplies many nutrients –but not in the ratio required for crops
• Physical problems –compaction, crown damage,leaf burn, salinity
• Nutritional problems –N can stimulate weeds, extra Kcan cause cation imbalance for dairy feed rations
• Excessive manure applicationmay buildup P concentrations to levelsof concern in water runoff
Summary-P Nutrition of Alfalfa
• Alfalfa roots grow best in nutrient-rich soil; Prepare the seedbed prior to planting and supplement in later years as needed
• Adequate P promotes vigorous N2 fixation, shoot development, and faster regrowth after cutting
• Uptake of P continues through the season and is harvested in large amounts. The P fertilizer source is not important
• Placement near the seedling boosts establishment and stand longevity
• Crop response to P is best predicted with a soil test and subsequent tissue testing
• Nutrient management is an essential key to profitability and efficient use of other inputs
International Plant Nutrition Institute (IPNI)655 Engineering Drive, Suite 110Norcross, GA 30092-2837Phone: 770-447-0335; Fax 770-448-0439Website: www.ipni.net
Reference 06128