Project HUMOR
Evaluation of the humus and nutrient effect of organic residues
Duration: 2019 – 2022
Contact: Dr. Martin Armbruster
Brief description
Within the joint project “Evaluation of the humus and nutrient effect of organic residues (HUMOR)”, standardized primary data on the chemical properties of 59 different organic residues were determined in sub-project 2 (Chemical characterization of residues and determination of their N and P dynamics in incubation experiments). The release of nitrogen (N) and phosphorus (P) from these residues was investigated under controlled conditions (constant temperature and soil moisture) in incubation experiments.
© LUFA Speyer
In addition, a vegetation trial (new crop test) was carried out with barley for 12 residues in order to determine the plant availability of the applied phosphorus and to compare it with the P release in the incubation trials.
Results
The organic residues examined from the groups of plant residues, manure of animal origin, fermentation residues and composts show a high variation of chemical parameters both between and within the residue groups. This concerns, among other things, the mineral content (C, N, P), their binding in inorganic or organic form and their solubility in various extraction agents. There are also major differences in the fiber fractionation. This makes it clear that the chemical analysis of organic residues, especially when they are purchased or used for the first time, can greatly improve their targeted use.
The incubation tests with the residues revealed large differences in the release of nitrogen and phosphorus during incubation. This indicates differences in the fertilizer effectiveness of the residues. Differences in the release of nitrogen and phosphorus in the incubation trials are related to the determined chemical parameters of the residues. With regard to nitrogen release, the total nitrogen content, the NH4-N content, the proportion of NH4-N in the total N and the C/N ratio of the residues were of importance here. At the beginning of the incubation trials, there was a good relationship between the total phosphorus content of the residues and the phosphorus release. Later on, good relationships developed with the C/N and C/P ratios of the residues. In a vegetation test with 12 selected residues, the relationship between the phosphorus release determined in the incubation test and the phosphorus fertilizer effectiveness was confirmed.
Knowledge of the chemical parameters and their significance for nitrogen and phosphorus release can therefore make an important contribution to the more targeted and efficient use of residues as fertilizers. This can improve material recycling in agriculture and thus contribute to resource conservation and a reduction in fertilizer costs.
Find out more about the project here.
