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St. Augustine Grass Phosphorus Requirement

St. Augustine Grass Phosphorus Requirement. Min Liu Advisor: J. B. Sartain Soil and Water Science The University of Florida May 27, 2005. Contents. Introduction and objectives Greenhouse hydroponic study - materials and methods;

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St. Augustine Grass Phosphorus Requirement

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  1. St. AugustineGrass Phosphorus Requirement Min Liu Advisor: J. B. Sartain Soil and Water Science The University of Florida May 27, 2005

  2. Contents • 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

  3. 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

  4. Introduction • 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

  5. Objectives 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 typesfor St.Augustine grass Field P study – To verify the results of greenhouse soil P study

  6. 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

  7. Greenhouse hydroponic study Experiment Design: CRD

  8. Solution Culture Techniques Reference Nutrient Conc. 2 Times of References are used

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

  10. Results and Discussion Solution P (ppb)

  11. Results and Discussion A B C C C C

  12. Results and Discussion A B BC CD CD D

  13. Results and Discussion A AB AB AB B B

  14. Results and Discussion A B C D E F

  15. Results and Discussion y = -0.3168 + 1.9427x - 0.7186x2 r2 = 0.96**, CV = 15.4 plateau = 1 critical x = 1.4

  16. Results and Discussion y = 0.5043 + 0.00643x - 0.0000209x2 r2 = 0.93*, CV = 15.5 plateau = 1 critical x =153

  17. Greenhouse hydroponic study Summary • 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

  18. 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

  19. Greenhouse soil P study • 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

  20. Expected Results --- Determine critical soil P levels critical tissue P conc. Tissue P levels • Meclich-1 P • WEP critical Soil P conc. Soil P levels

  21. Expected Results --- Determine P fertilization rates to reach critical soil P levels critical Soil P conc. • Meclich-1 P • WEP Soil test P levels minimum P rate P application rates

  22. Field P study Materials and methods • 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

  23. 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.

  24. QUESTIONS?

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