Analysis of crop density in case of bag silage

Gerd-Christian Maack



The feed crop preservation in silo bags was developed as an alternative technique to clamp and tower silos in 1969. Since that time the operating technique has been improved in many ways resulting in increased performance. In order to preserve feed crop quality and minimize aerobic deterioration during feed out the bulk density is also of particular importance.

One objective in the project was to analyse the bulk density at bags pressed in practice. To evaluate the results in order to their porosity, measurements of chopped maize at controlled density and dry matter content were made.

Another item of the study was the development of technical opportunities to control the pressing process because the brake pressure adjustment by the machine operator has often been a critical point in regard to the crop compaction. To conduct the necessary experiments a special experimental bagger was constructed.

The detected bulk density of the investigated crops maize, grass, alfalfa, maize ear silage and sugar beet pulps is at a similar level as measured in former studies at clamp silos. Also, in case of silage bags the density in the centre of the silo face is about 20 to 30 % higher than at the flanks and the top. The increase of the dry matter density with rising dry matter content is altogether low, though it varies depending on silage crop. The necessary increase of DM-density to keep porosity at a low level of 40 % in case of rising DM-contents could not be observed. For this reason it is important to store the crops in bags at appropriate DM-content.

For improved bag filling an automatic brake pressure adjustment unit has been developed by using the experimental bagger. Similar to the manual working press pressure adjustment, the film extension during the press process is used as a control variable. The film extension is calculated by controlling height and width of the pressed bag and the brake pressure is adjusted according to defined reference values of film extension. The permanent control of the bag extension and the pressure adjustment by low delay gives the opportunity to compact crops under nearly constant bag extension. Therefore the maximum achievable crop compaction by the current system can be better utilised.

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© Universitäts- und Landesbibliothek Bonn | Published: 24.02.2010