Phosphonic acid, potassium salt (1:1)

Toxicity to terrestrial plants

Additional information

All studiesreported are well conducted on the similar substance Reaction mass of dipotassium phosphonate and Phosphonic acid, potassium salt (1:1). Rationale for Read Across is attached at point 13.

The phytotoxicity of Potassium phosphonate (KH2PO3/K2HPO3)to three terrestrial plant species was established in an individual 21-day toxicity test according to OECD 208 at the Dr.U.Noack-Laboratorien, 31157 Sarstedt, Germany. Test plants comprised one monocotyledon (oats, Gramineae) and two dicotyledons (rape, Brassicaceae; soybean, Leguminosae). The test was conducted at the limit application rate of4.0 L product/ha. The test item was applied at test start on the soil surface after the seeds were sown. The test containers were bottom watered with nutrient solution as needed. Potential toxic effects of the test item were assessed on day 7, 14 and 21 by visual observations (phytotoxic effects, number of dead plants and number of emerged seedling) and on day 21, respectively by shoot height and shoot fresh weight determination. The test item did not cause any test item related visual phytotoxic effects at test end for all tested plant species at the limit concentration of 4.0 L/ha (sections8.3).

The results of the control for all plant species met the required validity criteria. Therefore, the test is considered to be valid.

The test item did not cause inhibitory effects ≥ 22 % on shoot height, shoot fresh weight (biomass) and rate of emergence to all plant species at the limit application rate of 4.0 L/ha.

The phytotoxicity of Potassium phosphonate KH2PO3 / K2HPO3(batch number:20130102-018) to three terrestrial plant species was established in 21-day toxicity testsaccording to OECD 227 at the Dr.U.Noack-Laboratorien, 31157 Sarstedt, Germany. Test plants comprised one monocotyledon (oats, Gramineae) and two dicotyledons (rape, Brassicaceae; soybean, Leguminosae). The test was conducted with the limit application rate of4.0 L product/ha. The test item was applied at test start to plant foliage which had reached the 2-3 true leaf stage. The plants were watered and fertilised from the bottom during the test with nutrient solution as needed. Potential toxic effects of the test item were assessed on day 7, 14 and 21 by visual observations (phytotoxic effects and number of dead plants) and on day 21 additionally by shoot height and shoot fresh weight determination. No phytotoxic effects were observed for the plant species oats, rape and soybean.

The results of the control for all plant species met the required validity criteria. Therefore, the tests are considered to be valid.

The test item did not cause inhibitory effects > 17 % on shoot height and shoot fresh weight (biomass) to all plant species at the application rate of 4.0 L/ha.

The effect of potassium phosphonate on terrestrial plants was tested in two terrestrial plant protocols, i.e. OECD 208 and OECD 227. The test were performed at a maximum application rate of 4 L/Ha representative for the conditions of use of potassium phosphonate.

Biological effects on terrestrial plants are deemed significant when >25% effect is observed in two plant species, or >50% in a single plant species used in the tests. In addition, no visible detrimental effects were noticed on any of the plant parts.

Since effects in both tests were clearly below 50% (maximum effect 22% and 17% in one single plant species for seedling emergence and vegetative vigour respectively) it can be concluded that no adverse effects on seedling emergence and growth, expressed as shoot height and shoot fresh weight, nor on vegetative vigour of the tested plants were observed.