St. Augustine Grass Phosphorus Requirement Min 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 lawn area 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, 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- nutrients source mg dm -3 Fe Sequestrene Fe B H 3 BO Mn MnCl 2.4H 2 O 0.05 Cu CuCl 2.2H 2 O Zn ZnCl Mo Na 2 MoO 4.2H 2 O Cl MnCl 2.4H 2 O CuCl 2.2H 2 O ZnCl 2 Macro- nutrients source mmol m -3 K+K+K+K+ K 2 SO 4 13 (0.5ppm) Ca 2+ Ca(NO 3 ) 2.4H 2 O 9+? Ca(H 2 PO 4 ) 2.H 2 O Mg 2+ MgSO 4.7H 2 O 10 NO 3 - Ca(NO 3 ) 2.4H 2 O NH 4 NO 3 NH 4 + NH 4 NO SO 4 2- MgSO 4.7H 2 O k 2 SO 4 H 2 PO 4 - Ca(H 2 PO 4 ) 2.H 2 O Times of References are used

Data to be collected: Tissue Growth Rates Tissue P Levels Turfgrass Quality Root Growth Rates

Solution P (ppb) Results and Discussion

CC C C B A

D CD BC B A

Results and Discussion A B B AB

Results and Discussion A B C D E F

y = x x 2 r 2 = 0.96**, CV = 15.4 plateau = 1 critical x = 1.4

Results and Discussion y = x x 2 r 2 = 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 Tissue P levels 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 Soil test P levels 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 study Expected 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?