Figures (3)  Tables (5)

    • Figure 1. 

      Effect of P rate (provided through TSP) and phosphite products on P uptake by creeping bentgrass, Run 1 (top) and Run 2 (bottom). Treatments with the same letter above the bars are not significantly different (α = 0.05) within an experiment and each rate of P fertilization.

    • Figure 2. 

      Effect of P rate (provided through TSP) and phosphite products on creeping bentgrass root dry weight, Run 1 (top) and Run 2 (bottom). Treatments with the same letter above the bars are not significantly different (α = 0.05) within an experiment and each rate of P fertilization.

    • Figure 3. 

      Mehlich-1 extractable phosphite (top) and phosphate (bottom) as affected by the addition of phosphite supplied as TKO (left) or phosphate supplied as TSP (right) at four rates of P.

    • mg·kg−1pH
      PKCaMg
      greenhouse-ryegrasRun 102.52827.4
      Run 2194270.518.55.7
      greenhouse- bentgrassRun 12973.523.54.9
      Run 2210.5110.531.54.7
      laboratory incubationMarvyn
      loamy sand      		236.546435.56.5
      †Mehlich 1 soil test extraction.

      Table 1. 

      Initial soil-test results† for all soil used in greenhouse and laboratory experiments.

    • Commercial trade nameManufacturerFormulated fromPercent PPercent
      from PO3      		Percent
      from PO4      		%N-P-KStudies Used
      TurfiteHeadland Amenity Ltd. Cambourne, Cambridgeshire, UKPhosphoric acid
      Ammonium phosphate
      Ammonium citrate      		8.975.924.18-9-0†ryegrass
      TKOGrowth Products. White Plains, NY 10603, USAPhosphorous acid
      Potassium hydroxide      		29.610000-0-22†ryegrass soil
      Title PhyteHarrell's. Lakeland, FL 33802, USAMono- and Di- Potassium phosphite15.0§10000-0-25†ryegrass bentgrass soil
      AludeCleary Chemical, Dayton, NJ 08810, USAMono- and Di- Potassium Salts of Phosphorous Acid11.0±1000n/abentgrass
      Triple super phosphatePiedmont Fertilizer Company. Opelika, AL 36801, USATriple superphosphate20.701000-20-0ryegrass soil
      † Guaranteed analysis does not include P contribution from phosphite. Manufacturer and formulation specifications for this product at the time of this work (newer product currently with NuFarm). § Calculated on 571 g·H3PO3·L−1, 1,455 g·L−1. ± Calculated on 401 g·H3PO3·L−1, specific gravity of 1.35.

      Table 2. 

      Nutrient/active ingredient content of phosphite/phosphate, phosphite and phosphate products for greenhouse perennial ryegrass, bentgrass, and laboratory soil incubation studies.

    • SourceANOVA
      Ryegrass study
      Top growth Dry weightTissue P contentP uptake
      Run1Run2Run1Run 2Run1Run2
      Harvest (H)−−**NS**
      P rate (R)NS*****NS**
      P source (S)NS*******
      R × PNS**NSNSNS**
      H × R−−NSNSNS*
      H × S−−**NS*
      H × R × P−−NSNSNS*
      SourceBentgrass study
      Tissue dry weightTissue P contentP uptakeRoot dry weight
      Run1Run2Run1Run2Run1Run2Run1Run2
      P rate (R)NSNS********NSNS
      P source (S)*********************
      R × PNSNS************
      *Significant at P = 0.05; ** significant at P = 0.01; *** significant at P = 0.001; NS = nonsignificant at P = 0.05.

      Table 3. 

      ANOVA table for perennial ryegrass and creeping bentgrass studies.

    • P Rate
      (kg·ha−1)      		Dry weight of topgrowth (g)
      P source
      TurfiteTKOTSP
      00.280.280.28
      130.37 ab††0.41 a0.32 b
      260.39 a0.43 a0.40 a
      400.48 a0.36 b0.41 ab
      520.43 a0.39 a0.36 a
      RegressionQ†NSQ
      † From linear regression (each column), Q = significant quadratic response within each P source; NS – no linear or quadratic response. †† From mean separation, means followed by the same letter are not significantly different from each other (alpha = 0.05), between P sources (each row), within each P rate.

      Table 4. 

      Effect of P rate and P source (TSP (phosphate), TKO (phosphite), Turfite (phosphate/phosphite)) on the dry weight of perennial ryegrass topgrowth. Run 2 of a greenhouse experiment.

    • P sourceP rate
      (kg·ha−1)      		Tissue P uptake (mg−1·pot−1)
      TurfiteTKOTSP
      Harvest 1, Run 200.030.030.03
      130.120.140.09
      260.180.170.17
      400.150.100.19
      520.150.120.26
      RegressionQ†NSL
      Harvest 2, Run 200.020.020.02
      130.11 a0.08 a0.08 a
      260.17 a0.15 a0.13 a
      400.30 a0.17 b0.15 b
      520.32 a0.23 b0.17 c
      RegressionLLL
      † From regression, L= significant linear, or Q = quadratic response within each P source and Harvest/Run, NS = not significant.

      Table 5. 

      Effect of P rate and P source (TSP (phosphate), TKO (phosphite), Turfite (phosphate/phosphite)) on P uptake by perennial ryegrass as affected by P source, two harvests in Run 2 of the experiment.