Epsilon Archive for Student Projects

Abstract

The eutrophication of inshore seas, lakes and watercourses is mainly due to leaching of nitrogen and phosphorus (P) from agriculture. Many efforts are made to reduce the lea-kage of phosphorus in Sweden and the Baltic Sea countries. Phosphorus is also a finite resource and the mining of good quality raw material gets more and more difficult. Se-dimentation dams in combination with filters is one relatively new method to separate P from run-off and drainage water from agricultural land. This study was a part of an IVL Swedish Environmental Research Institute’s project which tests the capacity and func-tion for separation of phosphorus in four phosphorus filters. The main focus in this study was to investigate the phosphorus fertilizing effect of recycled used filter material on barley. Such filters have earlier shown to have a liming effect on soils.

The hypotheses tested in this study where: 1) Phosphorus filters added to soil will improve the growth of the crop, 2) Phosphorus filters added to soil will improve the growth of the crop more on the unlimed soil than on the limed soil, and 3) Phosphorus filters added to soil will improve the phosphorus uptake by the plant. The hypotheses were tested in a greenhouse experiment with barley, cv Vilgott, where the four filters Filtra P, Polonite, Filtralite and Hyttsand were added to soil derived from a liming and phosphorus fertilization field trial (R3-1001) at Lanna in southwestern Sweden. The soil from the treatments used in the experiment has not been fertilized with phosphor-ous after the start of the experiment in 1936. The filters had then been used in the field for phosphorus separation for 16 months. To be able to separate the liming effect of the filters from the potential phosphorus effect, limed and unlimed soils from the field ex-periment were used in combination with/without phosphorus application. At harvest, after five weeks of growth, when the plants had reached on average growth stage DC 33, the plant development and symptoms of phosphorus deficiency were recorded. The dry matter content and phosphorus uptake as well as the content of nitrogen and carbon of the crop were analyzed. The filters and soils were also analyzed on its content of phosphorus (P-AL). The results were interpreted statistically with ANOVA.

Plants given phosphorus fertilizer grew much better than plants that were not, which showed that the conditions for discovering potential phosphorus effect due to the filters were favourable. The growth and the phosphorus uptake of barley neither improved nor were reduced due to the filters when they were added in proportion to their liming ef-fect. During this short term study tendencies were seen that filters affected the growth, development and phosphorus uptake of barley, why a filter effect cannot be excluded. It would have been interesting to track phosphorus in the filters by using isotope marked phosphorus or comparing filters with different phosphorus saturation rates. This could be combined in an experiment to investigate if a saturated filter releases phosphorus easier than a non-saturated filter when added to soil.