TY - THES A1 - Höft, Mattis T1 - Influence of humic acids on nutrient use efficiency of three phosphorus sources in a sandy soil N2 - A pot trial was conducted under greenhouse conditions to assess the effect of humic acid (HA) application in combination with rock phosphate (RP) on the plant phosphorus (P) nutrient use efficiency (NUE), in comparison to the performance of struvite (ST) and triple superphosphate (TSP) amended plants. A sandy soil, exhibiting a low P content, was used in combination with a lignite derived, liquid humic acid product, with a HA content of 4.8 %. Nine groups of perennial ryegrass (Lolium perenne L.) were set up as experimental plants, in replications of six, each containing 4.5 kg air dry soil with a P supply of 27 mg P kg-1 soil, causing P deficiency during the experiment. HA was applied at rates of 1, 30 and 100 mg kg-1 soil, directly to the soil as coated RP or as foliar application. Aboveground biomass was harvested biweekly, five times in total. Amendment performance was evaluated by analysing plant biomass, soil pH, plant phosphorus-, carbon-, nitrogen-, iron-, zinc-, manganese- and boron contents. The label doses of 1 mg kg-1 soil as well as 100-fold increases in HA concentration didn’t result in a significant difference in plant shoot or root growth and P NUE compared to untreated plants. Positive trends were displayed at higher foliar application rates. Plant tissue micronutrient concentrations of HA treated samples were generally lower and partly significantly lower than the control. The detected effects were accredited to the hormone-like influence of HA on plants’ metabolism and the ability to alter soil conditions. The lack of calcium in ST amended samples resulted in better plant P availability, significantly higher P uptake and better shoot biomass development. Trends show that ST could be applied in combination with HA to further increase plants P NUE in the future. KW - Humic acid KW - Phosphorus KW - Struvite KW - Rock phosphate KW - Triple superphosphate Y1 - 2018 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:hbz:1383-opus4-2978 ER -