1. Phosphorus Nutrition of Cotton
Prepared by:
Dr. Cliff Snyder
Dr. Mike Stewart
International Plant Nutrition Institute (IPNI)
Norcross, Georgia U.S.A.
Updated January 2007
International Plant Nutrition Institute

2. Outline - P Nutrition of Cotton
U.S. cotton yields since 1975
Growth and development of the cotton plant
Nutrient uptake
General P nutrition and response
P placement options
Conclusions
International Plant Nutrition Institute

3. U.S. Cotton Yield, 1975 to Present . . . An Increasing Trend
Lint, lb/A
Year
Cotton yields have trended upward in recent decades. Increased yields, especially with shorter-season cotton varieties, will require optimum fertility management to meet nutrient uptake demands and to replace harvested nutrients.
Source: USDA/NASS
Source: USDA-NASS
International Plant Nutrition Institute

4. A Production Timeline for Irrigated Cotton in the Texas High Plains
Approximate days
after planting
Approximate heat
units after planting 10 20 30 40 50 60 70 80 90
100
110
120
130
140
150
160
Emergence
Squaring
Peak bloom
Harvest
1st bloom
1st open boll
May
June
July
August
September
Nov
October
525
1060
1470
1640
2280
95% mature
In relation to production and management, the cotton plant has five main growth stages: 1) germination and emergence, 2) seedling establishment, 3) leaf area and canopy development, 4) flowering and boll development, and 5) maturation. An effective way of assessing the development, or progression of physiological events, of a cotton plant is with heat units or growing degree days. A heat unit is expressed in degrees Fahrenheit and is defined by the following equation:
Heat Unit = [(daily maximum temperature + daily minimum
temperature) ÷ 2] – 60.
This slide shows a timeline that generally describes the relationships among time, heat unit accumulation, and cotton development on the Texas High Plains.
Source: Dr. Randy Boman, Extension Agronomist-Cotton, Texas Cooperative Extension, Lubbock, TX.
Source: R. Boman
International Plant Nutrition Institute

5. Early Season Root Development of the Cotton Plant
Early-season root growth helps ensure that plants access moisture and nutrients efficiently. Any restriction in early root development may prevent rapid root and shoot expansion during peak growth periods, from squaring through peak bloom: about 60 to 100 days after planting.
Source: Oosterhuis, D.M Growth and development of a cotton plant. p In W.N. Miley and D.M. Oosterhuis (eds.), Nitrogen Nutrition of Cotton: Practical Issues. Proceedings of First Annual Workshop for Practicing Agronomists. American Society of Agronomy. Madison, WI.
Source: Oosterhuis, 1990
International Plant Nutrition Institute

6. Cotton Root Length as Affected by Days After Planting (Field Study)
Roots, ft/plant
Days after planting
4 true leaves
First bloom
Late bloom/early boll filling
Based on 36,000 plants/A, there were 9,545 miles of roots /A
One of the key functions of P is to encourage vigorous root growth and development. Healthy root growth promotes healthy shoot growth. Data in this slide are for a single growing season on a fertile Dewey silt loam soil in North Alabama. Cotton (Deltapine 51) lint yields were considered excellent for this soil, location, and year: 1,513 lb/A.
Maximum root length occurred at about 117 days after planting, or several weeks into boll filling.
Maximum root length occurred approximately 11 days before dry matter production peaked (128 days after planting).
After first bloom, about 70% of the cotton root system was located in the 0 to 6 and 6 to 12-in. soil layers.
Source: Schwab, G.J., G.L. Mullins, and C.H. Burmester Growth and nutrient uptake by cotton roots under field conditions. Comm. Soil Sci. Plant Anal. 31(1 &2):149-1.
Source: Schwab, Mullins & Burmester, 2000
International Plant Nutrition Institute

7. Dry Matter Accumulation, and Nitrogen and Phosphorus Uptake of Cotton
Nutrient uptake by cotton is directly related to dry matter accumulation, which follows a sigmoidal pattern, and is determined by water and nutrient supplies, radiation, and temperature. Phosphorus accumulation is directly proportional to dry matter accumulation, while nitrogen accumulation is slightly higher through most of the season. During the summer months nutrient uptake is greater than in the cooler spring months. The greatest nutrient demand occurs between first square and peak bloom.
Source: Dr. Dan Krieg, Texas Tech University, Lubbock, TX.
Source: D. Krieg
International Plant Nutrition Institute

8. Cotton Nutrient Uptake Compared to Yield
Where – Who
Year
Cotton Type
Lint Yield (lb/A) N
P2O5
K2O
- - lb per 100 lbs. of lint - -
GA-Olson
1942
Upland
760 18 8
CA - Bassett*
1970
Acala
1,450 10 3 11
Israel - Halevy*
1976
1,580 14 6 12
AL - Mullins
1990
880 20
LA - Breitenbeck
1993
1,230 13
AZ – Unruh*
1996
1,186 15 5 23
Pima
965 21 7 25
Removal in harvested crop
IPNI
6.7
2.9
4.0
Less P2O5 is required per pound of lint cotton produced, compared to N and K2O. The amount of P2O5 required varies with the cotton type (Upland, Acala, Pima) as well as the irrigation regime. Work by Mullins and Burmester (1990) reported no significant differences in nutrient uptake requirement among four cotton cultivars, at similar yield levels.
Cotton P requirement per 100 lb of lint is as great today as it was six decades ago. With increased conservation tillage technologies, much of the cotton acreage is being planted using stale seedbeds, strip tillage and no-tillage. Soil temperatures in these production systems are often cooler at planting time, which increases the need for optimum soil test P levels and sound P fertilization.
National average yields have increased from about 450 lb/A in 1975 to over 700 lb/A currently. Higher yields, coupled with increased conservation tillage, place an increased demand on P fertilization for profitable production.
Sources: Georgia: Olson, L.C. and R.P. Bledsoe The chemical composition of the cotton plant and the uptake of nutrients at different stages of growth. Bull Georgia Agric. Exp. Stn.
California: Bassett, D.M., W.D. Anderson, and C.H.E. Werkoven Dry matter production and nutrient uptake in irrigated cotton (Gossypium hirsutum). Agron. J. 62:
Israel: Halevy, J Growth rate and nutrient uptake of two cotton cultivars under irrigation. Agron. J. 68:
Alabama: Mullins, G.L. and C.H. Burmester Dry matter , nitrogen, phosphorus, and potassium accumulation by four cotton varieties. Agron. J. 82:
Louisiana: Breitenbeck, G.A. and D.J. Boquet Effects of nitrogen fertilization on nutrient uptake by cotton. p Proc. of the 1993 Beltwide Cotton Conferences.
Arizona: Unruh, B.L. and J.C. Silvertooth Comparisons between an Upland and Pima cotton cultivar: II. Nutrient uptake and partitioning. Agron. J. 88:
IPNI: International Plant Nutrition Institute website >
* Irrigated tests
International Plant Nutrition Institute

9. Cotton Peak Nutrient Uptake Rate 60 to 100 Days After PlantingGA
*CA
*Israel AL
1942
1970
1976
1990 N
3.8
1.8
4.1
3.5 P
0.7
0.3
0.8
0.6 K
2.5
3.0
3.1
* Irrigated tests
lb/A per day
Location and year
Peak daily uptake of P can exceed 0.6 lb P/A (1.4 lb P2O5/A). Failure to maintain the uptake demand during peak periods will result in plant stress, yield loss, and a decline in lint quality.
Note: Nutrient uptake rates in newer cotton varieties may peak sooner and occur over a shorter time interval, compared to older varieties.
Sources:
Georgia: Olson, L.C. and R.P. Bledsoe The chemical composition of the cotton plant and the uptake of nutrients at different stages of growth. Bull Georgia Agric. Exp. Stn.
California: Bassett, D.M., W.D. Anderson, and C.H.E. Werkoven Dry matter production and nutrient uptake in irrigated cotton (Gossypium hirsutum). Agron. J. 62:
Israel: Halevy, J Growth rate and nutrient uptake of two cotton cultivars under irrigation. Agron. J. 68:
Alabama: Mullins, G.L. and C.H. Burmester Dry matter, nitrogen, phosphorus, and potassium accumulation by four cotton varieties. Agron. J. 82:
Source: Mullins and Burmester, 1990
International Plant Nutrition Institute

10. P Functions of Phosphorus in Cotton Production
Essential for vigorous root and shoot growth
Promotes early boll development and hastens maturity
Helps overcome the effects of compaction
Increases water use efficiency
Necessary for energy storage and transfer in plants
A two-bale crop can take up more than 50 lb P2O5/A
International Plant Nutrition Institute

11. P Uptake by Modern Cotton Varieties – 880 lb/A5 10 15 20 21 35 49 63 77 91
105
119
Days after planting
P, lb/A
Shoots
Leaves
Burs
Seed
Averaged across four varieties
Deltapine 90, Stoneville 825, Coker 315, Paymaster 145
P uptake increases rapidly once cotton begins squaring and flowering. Phosphorus uptake continues to plant maturity, with more being allocated to seed at the expense of burs and leaves. Phosphorus levels should be high enough and plants should be vigorous enough to support P uptake and translocation from vegetative organs to fruiting structures as cotton bolls mature.
Source: Mullins, G.L. and C.H. Burmester Dry matter, nitrogen, phosphorus, and potassium accumulation by four cotton varieties. Agron. J. 82:
Source: Mullins & Burmester, 1990
International Plant Nutrition Institute

12. P Compartmentation by Developing Cotton Bolls
P, mg
Days After Pollination
Seed
Bur (x 2)
Fiber (x 2)
Mature boll oven-dry weight ~ 6.5 grams
This slide illustrates the importance of optimum P nutrition on seed development and the increase in seed P concentration with boll maturity. Lint formation and development depends on adequate and sustained P nutrition throughout the plant’s life cycle.
Note that concentration of P in the seed is much higher than in the cotton bur or fiber. The actual concentration of P in the bur and the fiber was multiplied by 2 to get the values to display on the graph. The P content of the bur and fiber declines as the cotton matures, while the seed P content continues to increase. Based on the data in this graph, the seed P concentration would be about 0.5%.
Bassett and others (1970) reported that seed had a concentration of to 0.61% P. The National Cotton Seed Products Association (NCSPA) lists the whole cottonseed (not delinted) P concentration as 0.56%. The NCSPA website is >
Sources:
Leffler, H.R Mineral compartmentation within the boll. Chapter 21, p In J.R. Mauney and J.McD. Stewart (eds.), Cotton Physiology. The Cotton Foundation. Memphis, TN.
Bassett, D.M., W.D. Anderson, and C.H.E. Werkoven Dry matter production and nutrient uptake in irrigated cotton (Gossypium hirsutum). Agron. J. 62:
Source: Leffler, H.R. 1986
International Plant Nutrition Institute

13. Reasons to Build Soil Test P
Increase root growth for efficient uptake of other nutrients
Capitalize on “good weather” years
Minimize risk associated with “bad weather” years
Raise soil productivity
Increase yield potential of all crops in the rotation
Improve grower profit potential
Rules of thumb for raising soil test P
6 to 14 lb P2O5 needed above crop removal to build soil test P by 1 lb/A on sandy loam to silt loam soils
To ensure proper seed and lint development, adequate soil P levels must be built and maintained. There are other important reasons to build soil test P levels into the high or medium to high range, as noted in this slide.
The amount of P2O5 required to raise soil test P levels depends on the soil texture (clay content), type of clay minerals, soil pH, presence or absence of free calcium carbonate, soil iron and aluminum content, soil organic matter content, crop yields, and harvest removal of P, as well as tillage system.
The best way to determine the amount of P2O5 required for a specific soil and management program is to soil test. Soil testing on a relatively frequent basis (at least every three years, and preferably every other year), will enable the farmer or crop adviser to establish a soil test response curve that is specific to that farming situation.
International Plant Nutrition Institute

14. Probability of a Phosphorus Response . . . An Example
Category definitions vary among laboratories
This table illustrates the general probability of response to P fertilizer under different soil P fertility levels. Note that neither the amount of yield increase with P addition, nor the amount of P fertilizer required, are identified with this general table. Only field research can identify the amount of fertilizer P required and the potential yield increase at a given soil test P level.
International Plant Nutrition Institute

15. Cotton Relative Yield Response to Mehlich 3 Soil Test P in North Carolina
Soil test for 95%
of maximum yield
Relative yield, %
A recent research report on soil test correlation work in North Carolina showed that Mehlich 3-P soil test of a Goldsboro sandy loam should be above about 25 parts per million (ppm) above about 60 lb/A, based on a 0 to 8-inch sampling depth) to achieve about 95% of maximum yield.
The authors suggested an economic critical Mehlich 3-P critical level of 33 ppm, or about 80 lb/A, on a 0 to 8-in. soil sample.
The corn-peanut-cotton rotation studied in this research resulted in a 24% annual decrease in soil test P per year.
The authors reported that about 33 lb of P2O5/A/year would be needed just to maintain the soil test P level in the optimum range. Optimum soil P fertility on this soil resulted in yields near the following levels: corn = 110 bu/A, peanuts = 4,500 lb/A, and cotton lint = 750 lb/A.
Source: Cox, F.R. and J.S. Barnes Peanut, corn and cotton critical levels for phosphorus and potassium on Goldsboro soil. Commun. Soil Sci. Plant Anal. 33(7 & 8):
Source: Cox, F.R. and J.S. Barnes, 2002
International Plant Nutrition Institute

16. 6-Year Average Cotton Response to P Rate and Tillage in Tennessee
lb P2O5/A per year
Lint, lb/A
Low initial soil P
The study was conducted from 1994 through 1999 on a Loring silt loam (loess) at Milan, TN to evaluate interactions of tillage, P rate, and K rate. Initial Mehlich 1-P soil test was low (< 5 ppm or 10 lb/A). The P data shown are for the 60 lb K2O/A rate.
Yields were increased with P fertilization in both tillage systems.
Even though the disk-till yields were greater than the no-till yields, the response to P fertilization was greater in the no-till system.
The critical fertilizer P rate to achieve 95% of the maximum cotton yield was determined to be 96 lb P2O5/A for the disk-till system and 80 lb P2O5/A for the no-till system, on this low P soil.
Source: Howard, D.D., M.E. Essington, J. Logan, R.K. Roberts and W.M. Percell Phosphorus and potassium fertilization of disk-till and no-till cotton. Cotton Science 5:
Source: Howard & others, 2001
International Plant Nutrition Institute

17. Soil P Levels After 3 Years of P Fertilization on loessial Silt Loam Soil in Tennessee
Mehlich 1 P, ppm at 0 to 6 in. depth
lb P2O5/A per year
Tillage & Year
DT=Disk-till
NT=No-till
Study initiated in spring 1994.
The authors stated, “. . . higher extractable (petiole and leaf) P levels in the no-till system suggest a higher P availability from surface broadcast application of P for no-till production than disk-till production.” The higher soil test P levels in the no-till system are consistent with that statement, but the lower yields in the no-till system may have also led to less removal of P in harvested seed and lint.
Source: Howard, D.D., M.E. Essington, J. Logan, R.K. Roberts and W.M. Percell Phosphorus and potassium fertilization of disk-till and no-till cotton. Cotton Science 5:
Source: Howard & others, 2001
International Plant Nutrition Institute

18. P Placement Options Broadcast
Banded 2 x 2 (2 in. to the side and 2 in. below seed)
Surface banded
Deep banded
In-furrow with the seed (rates are limited due to possible seedling damage and toxicity)
Rates of greater than 2.5 to 2.8 gal/A have been shown to reduce cotton stands and yield, and rates greater than 1.5 gal/A are not recommended (Burris et. al., 1992)
Source: Burris, E., E.R. Funderburg, B.R. Leonard, and R.L. Hutchinson The influence of starter ( ) fertilizer on cotton seedling growth and compatibility with selected in-furrow seed treatment pesticides. Beltwide Cotton Conference Proceedings. p
International Plant Nutrition Institute

19. Effects of P Placement on Relative Cotton Yield
Low P soil
(29 lb/A extractable P)
Relative yield, % b ab a
High P soil
(126 lb/A extractable P)
Relative yield, %
No significant differences
Study was conducted on Norfolk sandy loam at two separate locations, after different cropping and tillage histories. (Soil test P determined by N sulfuric acid-extractable)
Treatments:
No P2O5 (control)
15 lb P2O5/A applied directly on seed by hand
15 lb P2O5/A on seed and 35 lb/A in band 10 in. to side and 4 in. below seed
50 lb P2O5/A in bands 3 in. to each side and 2 in. below seed
50 lb P2O5/A mixed in row 4 in. deep and 6 in. wide
50 lb P2O5/A broadcast and disked in
On high P soil, there were no statistically significant differences.
On low P soil, treatments 2 through 6 were statistically equal, but treatment 2 was not statistically different from the control (0 lb P2O5/A)
Broadcast and incorporated full rates of P for cotton may work as effectively as seed-placed or banded placement at equal or lower P rates, on low P soils.
Source: Nelson, W.N., B.A. Krantz, C.D. Welch and N.S. Hall Utilization of phosphorus as affected by placement: II. Cotton and corn in North Carolina. Soil Sci. 68:
lb P2O5/A applied and placement method
Source: Nelson & others, See notes for application methods
International Plant Nutrition Institute

20. Effects of P Placement on Relative Cotton Root Length (Laboratory study)
Low P Dewey soil (CEC=10)
14 lb/A (7 ppm) Mehlich 1-P
Relative total root length % b a
High P Marvyn soil (CEC=5)
88 lb/A (44 ppm) Mehlich 1-P
Relative total root length, %
No significant differences
Study was conducted on two soils with different cation exchange capacity (CEC).
Addition of constant P rate to decreasing proportions of the soil volume resulted in stimulated root growth in the P-fertilized soil volume, relative to the non-fertilized soil:
Total root length (length in unfertilized soil plus P-fertilized soil) was not significantly affected by soil volume fertilized in the Marvyn soil (CEC=5), which had a high soil test P rating.
In the low-P Dewey soil, total root length increased with P addition. As the proportion of the soil volume receiving P fertilizer increased, total root length tended to increase.
Source: Mullins, G.L Cotton root growth as affected by P fertilizer placement.
Applied P per pot was identical within a soil
Source: Mullins, 1993
International Plant Nutrition Institute

21. Effects of P Placement on Percent of Roots in Fertilized Soil (Laboratory study)
Low P Dewey soil (CEC=10)
(14 lb/A Mehlich 1-P)
% of roots in P-treated volume
High P Marvyn soil (CEC=5)
(88 lb/A Mehlich 1-P)
% of roots in P-treated volume
Study was conducted on two soils with different cation exchange capacity (CEC).
Addition of constant P rate to decreasing proportions of the soil volume resulted in stimulated root growth in the P-fertilized soil volume, relative to the non-fertilized soil:
As fraction of soil volume receiving fertilizer increased, root length in P-treated volume increased.
Addition of P in both soils increased root growth in P-fertilized fraction relative to unfertilized fraction.
Increased root growth in fertilized soil is due to an increase in soil solution P concentration.
The degree of root stimulation in P-fertilized soil was similar for both the high P and low P soils.
These results indicate that a band application of P in these soils should stimulate root growth within the fertilized soil volume.
Source: Mullins, G.L Cotton root growth as affected by P fertilizer placement.
Applied P per pot was identical within a soil
Source: Mullins, 1993
International Plant Nutrition Institute

22. Effect of In-furrow Starter Fertilizer on Cotton Yield (Louisiana)
Year
Soil texture
Check
Starter
Difference
1990
Silt loam
1255
1400
145*
1991
1184
1191 7
1503
1586
83*
1992
878
889 11
922
911
-11
999
1040 41
Clay
515
697
182*
734
837
103*
1993
941
1174
233*
Average
992
1081 88
* Differences were significant a the 0.05 level of probability.
starter was applied at the rate of 1.5 gal/A.
All soils tested high to very high in P.
lint yield, lb/A
“Based on four years of research at a number of on-farm locations, in-furrow applications of 1.5 gal/A of or and surface band applications of 12 gal/A of or showed the most promise. Although significant yield increases were not recorded at every location in every year, starter treatments did not significantly decrease lint yields in any of the experiments. It should be noted that the starters applied in these trials were in addition to the base N-P2O5-K2O rates applied to all plots.”
“In-furrow applications of at rates greater than 1.5 gal/A (18 lb/A) are not recommended.”
Source: Kovar, J.L., E.R. Funderburg, and R.L. Hutchinson Starter fertilizer can improve growth and yield of cotton. Better Crops with Plant Food. Winter 1993/94. p
Source: Kovar et. al., 1993.
International Plant Nutrition Institute

23. Effect of Surface Banded Starter Fertilizer on Cotton Yield (Louisiana)
Year
Soil texture
Check
banded
Difference
1990
Silt loam
1,255
1,443
188*
823
895 72
1,045
1,032
-13
1991
1,184
1,331
147*
949
1,073
124*
1992
999
1,144
145
878
957
79*
1993
860
969
109*
Average
1,106
106
* Differences were significant a the 0.05 level of probability.
starter was applied in a 3 inch surface band at the rate of 12 gal/A.
All soils tested high to very high in P.
lint yield, lb/A
“Based on four years of research at a number of on-farm locations, in-furrow applications of 1.5 gal/A of or and surface band applications of 12 gal/A of or showed the most promise. Although significant yield increases were not recorded at every location in every year, starter treatments did not significantly decrease lint yields in any of the experiments. It should be noted that the starters applied in these trials were in addition to the base N-P2O5-K2O rates applied to all plots.”
Source: Kovar, J.L., E.R. Funderburg, and R.L. Hutchinson Starter fertilizer can improve growth and yield of cotton. Better Crops with Plant Food. Winter 1993/94. p
Source: Kovar et. al., 1993.
International Plant Nutrition Institute

24. Effects of Fertilizer Placement on Cotton Seedling Growth (Louisiana)
Check
12 gal/A
surface banded
1.5 gal/A
in-furrow
“Dramatic increases in early-season growth are sometimes observed when starter fertilizers are applied to cotton.”
Source: Kovar, J.L., E.R. Funderburg, and R.L. Hutchinson Starter fertilizer can improve growth and yield of cotton. Better Crops with Plant Food. Winter 1993/94. p
Source: Kovar et. al., High soil test P level
International Plant Nutrition Institute

25. Effect of Starter Fertilizer (11-37-0) on Cotton Root Length Density (Louisiana)
Seedling
Root length density, cm/cm3
Early bloom
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
2.0
0-4 inch
4-8 inch
Check
Surf. band (12 gal/A)
In-furrow (1.5 gal/A)
In-furrow (2.5 gal/A)
“Application of ammonium polyphosphate (APP) starter can also stimulate early-season root growth of cotton, even in soil with high levels of available P. As with shoots, the response does not occur every year at every location. In addition, by the early bloom stage, other environmental conditions probably influence root growth more than N-P fertilizer applied at planting, so that differences in root growth disappear.”
Source: Kovar, J.L., E.R. Funderburg, and R.L. Hutchinson Starter fertilizer can improve growth and yield of cotton. Better Crops with Plant Food. Winter 1993/94. p
Source: Kovar et. al., High soil test P level
International Plant Nutrition Institute

26. Effect of P Fertilizer and Delivery Method on three- year Average Irrigated Cotton Yield (Texas)
818 b
916
824 a
972
200
400
600
800
1000
Control
Pre-plant
Sidedress
LEPA
fertigation
P fertilizer application method
Lint yield, lb/A
The data in this slide are 3-year averages across 11 varieties. All treatments received 100 lb/A N, and P was applied at the rate of 40 lb P2O5/A. Preplant application was banded four weeks prior to planting. Sidedress applications (three) were made preplant, first square, and first flower. Fertigation was applied as a S at least four times starting at first square and continuing through peak bloom.
This study showed that P fertilization is important in optimizing cotton yield in the Texas High Plains. Delivery of P fertilizer through fertigation was more effective than other methods of application. Sidedress application did not produce yield significantly above the control because of root pruning. Yield increase from P fertilization was due to an increased number of bolls and an increase in boll size. The increased boll size observed with P fertilization was a function of increased micronaire (more mature fibers). See following slides for effects of P on boll number, size, and micronaire.
Initial 0 to 6 in. soil test P was high at 27 ppm (Olsen).
Source: Reiter, J.S. and D.R. Krieg Cotton response to multiple applications of phosphorus fertilizer. Great Plains Soil Fertility Conference Proceedings. p
Source: Reiter and Krieg - Means with same letter are not different at the 5% level
International Plant Nutrition Institute

27. P Fertilizer and Delivery Method effect on Boll Number in Irrigated Cotton (Texas)
P fertilizer application method 10 20 30 40 50 60
Control
Pre-plant
Sidedress
LEPA
fertigation
Bolls per sq. m 53 57 51 58
The data in this slide are 3-year averages across 11 varieties. All treatments received 100 lb/A N, and P was applied at the rate of 40 lb P2O5/A. Preplant application was banded 4 weeks prior to planting. Sidedress applications (three) were made preplant, first square, and first flower. Fertigation was applied as S at least four times starting at first square and continuing through peak bloom.
This study showed that P fertilization is important in optimizing cotton yield in the Texas High Plains. Delivery of P fertilizer through fertigation was more effective than other methods of application. Sidedress application did not produce yield significantly above the control because of root pruning. Yield increase from P fertilization was due to an increased number of bolls and an increase in boll size. The increased boll size observed with P fertilization was a function of increased micronaire (more mature fibers).
Initial 0 to 6 in. soil test P was high at 27 ppm (Olsen).
Source: Reiter, J.S. and D.R. Krieg Cotton response to multiple applications of phosphorus fertilizer. Great Plains Soil Fertility Conference Proceedings. p
Source: Reiter and Krieg
International Plant Nutrition Institute

28. Effect of P Fertilizer and Delivery Method on Boll Size in Irrigated Cotton (Texas)
1.54
1.58
1.6
1.66 1
1.1
1.2
1.3
1.4
1.5
1.7
Control
Pre-plant
Sidedress
LEPA
fertigation
P fertilizer application method
Lint per boll, g
The data in this slide are 3-year averages across 11 varieties. All treatments received 100 lb/A N, and P was applied at the rate of 40 lb P2O5/A. Preplant application was banded four weeks prior to planting. Sidedress applications (three) were made preplant, first square, and first flower. Fertigation was applied as a S at least four times starting at first square and continuing through peak bloom.
This study showed that P fertilization is important in optimizing cotton yield in the Texas High Plains. Delivery of P fertilizer through fertigation was more effective than other methods of application. Sidedress application did not produce yield significantly above the control because of root pruning. Yield increase from P fertilization was due to an increased number of bolls and an increase in boll size. The increased boll size observed with P fertilization was a function of increased micronaire (more mature fibers).
Initial 0 to 6 in. soil test P was high at 27 ppm (Olsen).
Source: Reiter, J.S. and D.R. Krieg Cotton response to multiple applications of phosphorus fertilizer. Great Plains Soil Fertility Conference Proceedings. p
Source: Reiter and Krieg
International Plant Nutrition Institute

29. P fertilizer application method
Effect of P Fertilizer and Delivery Method on Micronaire of Irrigated Cotton (Texas)
P fertilizer application method
Micronaire 20 25 30 35 40 45
Control
Pre-plant
Sidedress
LEPA
fertigation
35.6
39.3
36.6
39.7
Premium range 37-42
The data in this slide are 3-year averages across 11 varieties. All treatments received 100 lb/A N, and P was applied at the rate of 40 lb P2O5/A. Preplant application was banded four weeks prior to planting. Sidedress applications (three) were made preplant, first square, and first flower. Fertigation was applied as a S at least four times starting at first square and continuing through peak bloom.
This study showed that P fertilization is important in optimizing cotton yield in the Texas High Plains. Delivery of P fertilizer through fertigation was more effective than other methods of application. Sidedress application did not produce yield significantly above the control because of root pruning. Yield increase from P fertilization was due to an increased number of bolls and an increase in boll size. The increased boll size observed with P fertilization was a function of increased micronaire (more mature fibers).
Initial 0 to 6 in. soil test P was high at 27 ppm (Olsen).
Source: Reiter, J.S. and D.R. Krieg Cotton response to multiple applications of phosphorus fertilizer. Great Plains Soil Fertility Conference Proceedings. p
Source: Reiter and Krieg
International Plant Nutrition Institute

30. Conclusions
Adequate P nutrition is critical in optimizing yield, quality, and profit in cotton production.
While placement of P fertilizer is not as important as in the production of many other crops, banding P can increase yields in some situations (e.g., reduced or no-till, compacted soil conditions).
Soil test levels should be maintained in the medium to high range to assure consistent production, and that P does not limit cotton yield and quality.
International Plant Nutrition Institute

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International Plant Nutrition Institute