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The silaging qualities of sunflowers


Sunflowers are a water-rich, non-wilting and therefore hard to silage feed crop. While in bloom their dry matter content is only 12 to 16 % and while the seeds form this grows to just a little over 20 % for the whole plant.

According to data from the USA (Panciera et al., 2003), the dry matter content to be expected in whole plants of oil sunflowers whose seeds have almost all matured is only some 23 %. This means that one will always have to take great amounts of silage effluent into account. To reduce the water content, an American author (Hoppe, 1997) recommends to only harvest the field crop after frost.

When sunflowers are in the state of ripeness described above, they consist mainly of stalks with lots of water inside, soft flower heads and oil-containing seed. Their leaves are insignificant. After chopping and compacting, a soft mass results. Since this can hardly be driven on, silaging pure sunflowers in horizontal silos of an appropriate silage height is impossible. And because creating mixed silage of sunflowers and silo maize by afterwards combining and mixing these two components is hardly possible either, planting a mixture of sunflowers and maize is generally recommended in the USA.

Sunflowers contain relatively little sugar and have a very high buffer capacity, almost identical to that of alfalfa. This is due to the high content of ash constituents which act like a base. The average sugar/buffer capacity quotient (S/BC) is approx. 1.5 (Weißbach, 1964). When assuming 23 % dry matter (DM) this results in an average fermentation coefficient (FC) of only 35, calculated using the equation

                                      FC = DM[%] + 8 S/BC,

qualifying sunflowers as medium to hard to ferment.

Furthermore, using the sugar/buffer capacity quotient of whole sunflower plants, using the equation (Weißbach et al. 1974)

                                     DMmin [%] = 45 ? 8 S/BC

results in a minimum dry matter content (DMmin) of 33 % for butyric acid free silage. This means that there is a shortage of some 10% of dry matter in the silage crop (33 - 23 %), if one wants to have the certainty of a good silage quality. This difference necessitates the use of a highly effective silage additive (mode of action and range of application = 1 a).


The following procedure can be recommended for silaging whole sunflower plants:

Await the first frost and then wait for a number of days to allow the dry matter content in the field crop to increase.

Add 2 - 3 litres of KOFASIL LIQUID per ton during harvesting to prevent butyric fermentation.

Silage in plastic tubes to prevent problems of having to drive over the silage.

22- 10-2007,  Prof. Dr. Weißbach