St. Augustine Grass

Phosphorus RequirementMin Liu

Advisor: J. B. Sartain

Soil and Water Science

The University of Florida

May 27, 2005

• Introduction and objectives

• Greenhouse hydroponic study - materials and methods; - results and discussion - summary

• Greenhouse soil P study - materials and methods; - expected results

• Field P study - materials and method - expected results

Contents

Introduction

• Distribution of St. Augustine,coverage about 65% home lawnarea in Florida

• Attention directed towards P fertilization of Florida lawn grasses, eutrophication

• A typical Florida soil is sandy and acidic, and the potential for P leaching exists

• Distribution of St. Augustine

• P requires to be scrutinized and monitored to reduce the amount of P that ends up as runoff or leachate

• P fertilization of Florida lawn grasses is based on soil tests

• Little information exists relative to the exact P requirement of Florida lawn grasses and fertilization levels

Introduction

Greenhouse hydroponic P study - To identify the critical tissue P concentration of the St. Augustine grass using solution culture techniques

Greenhouse soil P study – To determine the critical soil P levels and the P fertilization levels on two different soil types for St. Augustine grass

Field P study – To verify the results of greenhouse soil P study

Objectives

Greenhouse hydroponic study Materials and methods

• Six starting levels of P in solution (0, 1.24, 6.2, 31, 155 and 775 ppb ), replicated 5 times

• A total of 30 experimental units

• Study period: June 27, 2004 -- March 14, 2005

• Sods were taken from Hort. Unit, the initial tissue P was high

• Soils washed away from roots, then grass cut into size of the solution tub and put onto the screen of the solution tub

Experiment Design: CRD

Greenhouse hydroponic study

Solution Culture Techniques Reference Nutrient Conc.

Micro-Micro-nutrientsnutrients sourcesource mgmg dmdm-3-3

FeFeSequestrene Sequestrene Fe330Fe330 0.060.06

BB HH33BOBO33 0.050.05

MnMn MnClMnCl22.4H.4H

22OO 0.050.05

CuCu CuClCuCl22.2H.2H

22OO 0.0020.002

ZnZn ZnClZnCl22 0.0050.005

MoMo NaNa22MoOMoO

44.2H.2H22OO 0.0050.005

ClCl MnClMnCl22.4H.4H

22OO 0.0720.072

CuClCuCl22.2H.2H

22OO

ZnClZnCl22

Macro-Macro-nutrientsnutrients sourcesource mmol mmmol m-3-3

KK+ + KK22SOSO44 13 13 (0.5ppm)(0.5ppm)

CaCa2+2+ Ca(NOCa(NO33))22.4H.4H

22OO 9+?9+?

Ca(HCa(H22POPO

44))22.H.H22OO

MgMg2+2+ MgSOMgSO44.7H.7H

22OO 1010

NONO33

-- Ca(NOCa(NO33))22.4H.4H

22OO 18+8.518+8.5

NHNH44NONO

33

NHNH44

++ NHNH44NONO

33 8.58.5

SOSO44

2-2- MgSOMgSO44.7H.7H

22OO 10+6.510+6.5

kk22SOSO44

HH22POPO44

-- Ca(HCa(H22POPO

44))22.H.H22OO 0.04 -- 250.04 -- 252 Times of References are used

Data to be collected:

• Tissue Growth Rates

• Tissue P Levels

• Turfgrass Quality

• Root Growth Rates

0

1

2

3

4

5

6

7/19 8/18 9/17 10/17 11/16 12/16 1/15 2/14 3/16 4/15

Month/Day (2003-2004)

Tis

sue

P (

g kg

-1)

0

1.24

6.2

31

155

775

Solution P

(ppb)

Results and Discussion

Results and Discussion

Relationship between the solution P concentration and tissue Pconcentration on day 148

00.5

11.5

22.5

33.5

0 1.24 6.2 31 155 775Solution P (ppb)

Tiss

ue P

(g k

g-1

)

C C C CB

A

Relationship between the solution P concentrationand root P concentration on day 148

0

0.5

1

1.5

0 1.24 6.2 31 155 775

solution P (ppb)

Roo

t P (g

kg

-1)

Results and Discussion

DCD CD

BC

B

A

Results and Discussion

1

1.5

2

2.5

3

3.5

0 1.24 6.2 31 155 775

Solution P (ppb)

Ro

ot

gro

wth

ra

te

(g m

-2 d

ay-1

)

A

B B

AB AB AB

Results and Discussion

1

2

3

4

5

6

7

8

9

0 1.24 6.2 31 155 775

Solution P (ppb)

Mea

n t

urf

qu

alit

y (1

-9)

AB

CD

EF

Results and Discussion

Tissue P (g kg-1)

0.5 1.0 1.5 2.0 2.5 3.0Tis

sue

gro

wth

rat

e (g

m-2

day

-1)

0.4

0.6

0.8

1.0

1.2

y = -0.3168 + 1.9427x - 0.7186x2

r2 = 0.96**, CV = 15.4

plateau = 1 critical x = 1.4

Results and Discussion

Solution P (ppb)

0 100 200 300 400 500 600 700 800

Tis

sue

gro

wth

rat

e (g

m-2

day

-1)

.2

.4

.6

.8

1.0

1.2

y = 0.5043 + 0.00643x - 0.0000209x2

r2 = 0.93*, CV = 15.5

plateau = 1 critical x =153

• Phosphorus treatments increased tissue and root P levels

• The best turf quality was achieved by the highest P treatment

• Turfgrass receiving 31 ppb P gained the highest root growth rate

Greenhouse hydroponic study Summary

• The critical solution P concentration was 153 ppb

• The critical tissue P level was 1.4 g kg-1 on dry weight basis for the optimum growth

• It needs further research in soil to determine the minimum fertilization level of St. Augustine grass

Greenhouse hydroponic study Summary

• Five P fertilization levels (0, 1/16, 1/8, 1/4, and 1/2 lbs P/1000sqft (about 24 ppm)), concentrated superphosphate,run 16 wks

• Two soils: deep sand low in P and flatwood soil with moderate P levels; replicate 5 times and total of 50 exp. units

• Take tissue harvest every 2 wks, analyze for tissue P

• Take visual quality rating every 2 wks

• Take soil samples 8 and16 wks after P is applied, analyze for M-1 and WEP

• Take leachate samples on 1, 2, 4, 8, 12, 16 wks, analyze for P

• Take root sample at the determination day

Greenhouse soil P study

Expected Results

--- Determine critical soil P levels

Soil P levels

Tis

sue

P le

vels critical tissue P conc.

critical Soil P conc. • Meclich-1 P

• WEP

Expected Results --- Determine P fertilization rates to reach critical soil P levels

P application rates

Soi

l tes

t P

leve

ls

• Meclich-1 P

• WEP

critical Soil P conc.

minimum P rate

• Five P fertilization levels (0, 1/16, 1/8, 1/4, and 1/2 lbs P/1000sqft) concentrated superphosphate, run 16 wks after P treatments applied

• Two locations: deep sand low in P and flatwood soil with moderate P levels; replicate 5 times and total of 50 exp. units

• Take tissue harvest every 2 wks, analyze for tissue P

• Take visual quality rating every 2 wks

• Take soil samples 4, 8 and 16 wks after P is applied, analyze for M-1 and WEP for soil depth of 0-10 and 10-20cm

• Take root sample at the determination day

Field P study Materials and methods

Field P studyExpected Results

Essentially the same as greenhouse soil P study

since the field study is just a verification

Impacts: St. Augustine grass can be grown with and fertilized with P with minimum environmental impact.

QUESTIONS?QUESTIONS?