Experimental design
In the first experimental setup (first year of the trial), broiler chicken manure was stored under a roof in 1m³ boxes. The boxes were enclosed on all four sides and open only at the top. Rainfall was simulated by pouring the appropriate amount of water over the open box once a week using a watering can. An outlet was installed at the bottom of the box, allowing the resulting leachate to drain out and be measured.
In the first year of the trial, the following variants were investigated with three repetitions:
- 3x broiler chicken manure under roof
- 3x broiler chicken manure under roof irrigated with 800mm annual rainfall
- 3x broiler chicken manure under roof irrigated with 1600mm annual rainfall
The storage period was approximately 9 months.
In the second year of the experiment, two broiler chicken storage trials (under a roof, 800mm) were repeated and a third variant, "laying hen manure stored under a roof", was included in the experimental design.
- 3x broiler chicken manure under roof without fleece
- 3x broiler chicken manure under roof, irrigated with 800mm annual rainfall, covered with fleece
- 3x laying hen droppings under roof without fleece
In addition, three large outdoor storage heaps were created on a storage platform with a seepage trough, as well as a broiler chicken manure heap with and without a laying hen manure heap with compost fleece cover.
- Outdoor storage, laying hen manure with fleece – annual rainfall total 1009 mm*
- Outdoor storage, broiler chicken manure with fleece - annual rainfall total 1009 mm*
- Outdoor storage, broiler chicken manure without fleece - annual rainfall total 1009 mm*
* Data from the Irdning-Gumpenstein weather station for the climate normal period 1961 - 1990
In order to better evaluate the data obtained, manure samples were collected from practical farms, analyzed and compared with the experimental data.
Emission measurements to determine ammonia emissions were only carried out on two days with a short time interval between them.
Results
Nutrient losses were calculated based on the quantity and nutrient load of the leachate. No leachate was observed in the "under-roof" storage variants without irrigation.
The variants with simulated rainfall showed considerable nutrient losses in the form of nitrogen and potassium. In the 800 mm rainfall variant, the broiler chicken manure lost 2.27–2.83 kg; in the 1,600 mm variant, there were 7.6 kg of nitrogen losses per ton of fresh mass due to leachate.
In the outdoor storage trials, nitrogen losses of 0.98 kg were measured for broiler chicken manure without fleece cover, and 0.04 kg for the broiler chicken manure variant with fleece cover. The laying hen manure variant with fleece cover resulted in losses of 0.11 kg nitrogen per ton of fresh mass. The significantly lower leaching losses in the field storage of broiler chicken manure compared to the artificially irrigated storage variant are likely due to the buffering effect of the broiler chicken manure. Greater mass can absorb more water, thus reducing nutrient loss through leachate. The emission measurements showed a clear correlation between the under-roof storage variant and the irrigated variants. The latter exhibited a significantly higher outgassing potential. These results lead to the following conclusions:
- Laying hen manure should always be stored under a roof.
- Broiler chicken manure should ideally be stored under cover in areas with annual rainfall exceeding 500 mm . If stored outdoors in field heaps, covering with compost fleece is advisable .
