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Materials and Methods
On September 7th, 2006 Agrostis stolonifera var. Providence was sown at a rate of 6 g m2 into a silica sand medium. The sand was contained in 22x22cm pots, situated in a greenhouse at Michigan State University. After germination, three separate treaments were initiated. Treatment one (control) consisted of applying 150 ml of Hoagland’s No. 2 solution on a weekly basis (Appendix 1). Treatments two (phosphate) and three (phosphite) consisted of applying 150 ml of Hoagland’s No.2 solution minus the recommended amount of NH4H2PO4 on a weekly basis (Appendix 1). Treatments two and three were supplemented with NH4H2PO4 at a rate of 0.2 ml/L of Hoagland’s until October 10th. Treatment two was then supplemented on a weekly basis with 3-18-18, diluted 100 times to give 0.18% phosphate, beginning on October 10th. Treatment three was supplemented on a weekly basis with 1-0-26, diluted 100 times to give 0.18% phosphite, beginning on October 10th. Twelve ml of both 3-18-18 and 1-0-26 solutions were evenly sprayed per treatment pot at each application. All treatment pots received water every second day throughout the experiment at a rate of 0.2 L per pot per watering.
Grass dry weights were collected on a weekly basis beginning on October 17th. Leaf tissue phosphorus was measured colorimetrically according to the method of Murphy and Riley (1962), beginning on October 10th. Dry root weights were measured at the end of the experiment. This was carried out by taking cores measuring 7.5 x 7.5 cm from the grass pots. Sand was washed from the cores roots, which were subsequently dried for 72 hours. The grass was then removed from the samples and the root weights measured. Turfgrass density was measured on a scale of 1-9, with 9= full cover and 1=no grass
cover.
The experiment was carried out as a randomized complete block design with six replications. Analysis of variance (ANOVA) was carried out using Statistical Analysis Systems (SAS) (SAS Institute, 2001) and PROC MIXED was used for multiple factor analyses of variance. Fisher’s least significant difference (LSD) was used for mean separation, when effects were significant at P ? 0.05.
Results
Grass Dry Weight
The control treatment had significantly higher grass dry weights compared to both the phosphite and phosphate treatments on all measurement dates (Table 1). The phosphate treatment had significantly higher grass dry weights compared to the phosphite on all measurement dates (Table 1).

Table 1. Mean grass dry weight (g m2) for treatment main effect

Tissue Phosphorus Concentration.
No significant differences were found between treatments two and three prior to phosphite (treatment three) and phosphate (treatments two) application (October 10th). However, the control treatment had on this measurement date significantly higher tissue P concentrations than both treatments two and three (Table 2). The control treatment had significantly higher tissue phosphorus concentrations compared to both the phosphite and phosphate treatments on all measurement dates (Table 2). The phosphate treatment had significantly higher tissue phosphorus concentrations compared to the phosphite on all
measurement dates (Table 2).

Root Mass.
Both control and phosphate treatments had significantly higher root mass weights than the phosphite treatment, although no significant difference in root mass weight was found between the control and phosphate treatment (Table 3).













Grass Density
The control treatment had significantly higher grass density compared to both the phosphite and phosphate treatments. (Table 4). The phosphate treatment had significantly higher grass density compared to the phosphite treatment (Table 4).














Discussion
Phosphorus is one of the essential elements for normal growth and development of plants. In fertilizers, phosphorus is usually found in the form of phosphoric acid (H3PO4) , which readily disassociates to release hydrogen phosphate (HPO42-) and dihydrogen phosphate (H2PO4-) (Brunings et al., 2005). Both of these ions can be taken up by the plant but H2PO4
- more readily (Street and Kidder, 1989). Once inside the plant, both ions are
mobile (Fu and Dernoeden, 2005). Phosphoric acid should not be confused with
phosphorous acid (H3PO3), which is also known as phosphite (Fu and Dernoeden, 2005, Brunings et al., 2005). Phosphorous acid does not get readily converted into phosphate, which is the primary source of P for plants (Ouimette and Coffey, 1989). Some soil bacteria may be able to absorb and assimilate phosphate in dead tissue to produce energy and phosphate (McDonald et al., 2001).

McDonald et al. (2001) reported that phosphite translocates readily throughout the plant, but does act as a source of P nutrition. This is in agreement with the findings of this research. Even though application of phosphite in this trial did increase tissue P concentrations, it is likely that this elevation was due to the plant absorbing the phosphorus but not utilizing this P source, as shown in the results where the phosphate treatment significantly increased grass growth, turfgrass density and root mass compared to the phosphite treatment.

Research has shown that applications of phosphite containing fungicides, such as Chipco Signature which is an organic phosphate fungicide have increased turfgrass color and quality (Ray and Dernoeben, 2005). Tredway and Butler (2005) suggested phosphite containing compounds may have beneficial physiological effects on turfgrass under heat and drought stress. It should also be noted that the experiment carried out by Ray and Dernoeden (2005) was on an established golf green unlike this trial.

Conclusion
Phosphorus acid (Phosphite) applications appear to have limited if any influence on turfgrass growth and development when applied to a newly sown turfgrass sward.

References
Brunings, A.M., Datnoff, L.E., and Simonne, E.H.. 2005. Phosphorous acid releases the phosphonate ion (HPO32-), also called phosphite, upon disassociation. HS1010, Horticultural Sciences Department, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida.
Fu, J., and Dernoeden, P.H. 2005. Turf quality and carbohydrate metabolism in
response to phosphonate, phosphite and phosphate applications to creeping bentgrass. 2005 Turfgrass Pathology, Weed Science and Physiology Research Seminars. Department of Natural resource Science and Landscape Architecture. University of Maryland.
McDonald, A.E., Grant, B.R., and Plaxton, W.C. 2001. Phosphite (phosphorous acid): Its Relevance in the Environment and Agriculture and Influence on Plant Phosphate Starvation Response. J. Plant Nutr. 24:1505-1519. Ouimette, D.G., and Coffey, M.D. 1989. Phosphonate Levels in Avocado (Persea americana) Seedlings and Soil Following Treatment with Fosethyl-Al or Potassion Phosphonate. Plant Dis. 73:212-215.
Street, J.J. and Kidder, G.. 1989. Soils and plant nutrition. UF/IFAS, Fla. Coop. Ext. Serv. Fact Sheet SL-8.
Tredway, L.P. and Butler, E.L. 2005. Evaluation of fungicides for maintenance of summer quality in creeping bentgrass, 2004. Fungicide and Nematicide tests 60:1-2.

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