**6. Chemical additives on the top of the silos**

**Figure 3.** Effects of two covering system on estimated milk yield (kg/ton) of corn silages. Standard system = a single sheet of polyethylene (PE) film; OB system = oxygen barrier film between the silo wall and forage and covered by a

An environmental objective is to reduce the quantity of plastic used in agriculture, and there may be opportunity for achieving this by reducing the use of the plastic film for sealing silos. However, horizontal silos produce less plastic wastes than most other systems that use PE film for air tightness. Round bale silage requires at least 5.5 kg of plastic/ton DM. Stack silos use

A study was conducted to determine whether the PE film could be replaced with bio-based biodegradable films [18]. A standard 120-μm-thick white-on-black PE film and two different 120-μm-thick biodegradable plastic films were used to produce the silage bags for that experiment. The results of this research showed that the development of new degradable materials to cover silage could be possible. In addition, the authors recommended that further research should be undertaken to improve the blend for enhancing film stability over time and

To prevent deterioration in horizontal silos, the common practice is to use plastic film held in place with used car tires. Tires have been widely used because of their low cost and ready availability. In a study reported by Ruppel [19], there was a reduction in the temperature and improved protein availability of hay crop silage when the number of tires per square meter increased. The effects of several covering methods on reduction in the silage losses in the top

The results of a study on different silage sealing systems were presented by Borreani and Tabacco [20]. A farm bunker silo was covered with a single white-on-black sheet. Half of the

) and sand bags along the shoulders

about 1.3 kg of plastic/ton DM, four times less than the round bale silage system [5].

second layer of PE film. *Source*: Lima et al. [16].

58 Advances in Silage Production and Utilization

its resistance under outdoor conditions.

**5. Weighting the plastic cover**

resulted in lower losses [19].

layer concluded that higher tire density (30 tires per 10 m2

**4.3. Biofilms**

Especially in warm climates, whole-crop cereal silages such as corn, sorghum, and wheat are susceptible to aerobic deterioration. This is because aerobic yeasts are most active at 20–30°C [22]. Therefore, efforts need to be made to protect the silage near the surface when PE films are used. A research evaluated the application of additives (sodium benzoate and *Lactoba‐ cillus buchneri*) directly to the top of the silage and concluded that sodium benzoate applied at a 2 g/kg rate was the most suitable additive to improve the fermentation, reduce the aerobic deterioration, and preserve the nutrients of corn silage at the top of bunker silos [23]. Results from this study showed that the *in vitro* digestibility of the silage at the core and those treated with sodium benzoate were above 640 g/kg, whereas silages untreated and treated with two strains of *L. buchneri* had values close to 600 g/kg (**Figure 4**). According to the authors, under field conditions, the strains may have had their growth affected by high temperatures, and thus, chemical additives present more robust effects than biological ones when applied at the top.

**References**

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[2] Savoie, P. and J. C. Jofriet. 2003. Silage storage. In D. R. Buxton, R. E. Muck, and J. H. Harrison, eds. Silage Science and Technology. Vol. 42. Madison, WI, Am. Soc. Agron.,

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[11] Griswold, K. E., E. E. McDonell, L. Kung, Jr., and P. H. Craig. 2010. Effect of bunker silo sidewall plastic on fermentation, nutrient content and digestibility of corn silage. J.

[12] Bernardes, T. F., L. G. Nussio, R. C. Amaral, and A.L.B. Schogor. 2009. Sealing strategies to control the top losses of corn silage. In Proc. 15th Int. Silage Conf., Madison,

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**Figure 4.** Effects of additives on *in vitro* DM digestibility in different zones of the bunker corn silage. Core = silage in the core of the silo; CLB = silage treated with commercial *Lactobacillus buchneri*; ILB = silage treated with indigenous *L*. *buchneri*; SB = silage treated with sodium benzoate. *Source*: Da Silva et al. [24].
