The Accumulation of Phosphorus in Maize Biomass Treated by Thermally Processed Sewage Sludge

B.Sc. Fevan Tafesse

Master's thesis

Abstract:

A three-year (2018 - 2020) pot experiment has been set up with maize and two soils (Žamberk and Citov) to investigate the effect of sewage sludge and sewage sludge biochar on the yield and uptake of P by the maize plants. For this purpose, 12 treatments: control, no sludge (NK), fresh sludge, oven dry sludge, biochar produced at 5 different temperatures (BC 220, 320, 420, 520 and 620 °C), triple super phosphate (TSP) 100% P, TSP 50% P, and rock phosphate (RP) 100% P have been established. Eight maize plants were sown at the beginning May, thinned to four at the 14 days after sowing, regularly irrigated to 60% of the respective soil maximum water holding capacity. The maize plants were then harvested at the full maturity, dry biomass weighed, the concentration of P analyzed, and the total removal of P calculated. In the acidic Žamberk soil (pH = 5.2), all the amendments (fresh and dry sludge, all biochars) and P fertilizer treatments had higher maize yield than no sludge (NK) treatment at all three-growing seasons except the TSP 50% at 2019. However, in the neutral Citov soil (pH = 7.3), RP 100% in 2018, all P fertilized treatments in 2019 and all amendments except BC 520 in 2020 had lower maize biomass than no sludge (NK) treatments of the respective year. Comparison between all biochar treatments the BC 220 had the highest maize biomass yield. Comparing biochar and P fertilized treatments, the TSP 100% had higher maize yield than all other biochars, but the TSP 50% and RP 100% had equal or less biomass yield than all biochar treatments. The cumulative removal of P in Žamberk over three years was higher in all amendments and P fertilized treatments than the no sludge (NK) treatments. It was also evident that the highest portion of P removed was at the first growing season. However, in Citov soil the higher cumulative maize biomass compared to no sludge (NK) treatment was only at the TSP 100%, BC 320, BC 420 and BC 620 treatments, while the rest exhibiting lower P removal than the no sludge (NK) treatments. This was consistent with the PUE, in which the positive PUE was only at the TSP 100%, BC 320, BC 420 and BC 620 treatments. Therefore, based on the findings of this study, the better performance of sewage sludge and sewage sludge biochar in acidic soil could be expected with a possible effect longevity up to three years. Additionally, the sewage sludge and sewage sludge biochar could potentially substitute TSP and RP fertilizers.

Keywords

Sewage sludge biochar, P fertilizers, Maize yield and Uptake of P, Sewage sludge

Language used: English

Date on which the thesis was submitted / produced: 23. 4. 2021

Thesis defence

• Supervisor: prof. Ing. Pavel Tlustoš, CSc. dr. h. c.

Czech University of Life Sciences Prague

Faculty of Agrobiology, Food and Natural Resources

Master programme / field:
Zemědělská specializace / Tropical and Subtropical Agriculture