# Feasibility of Utilizing Biodegradable Plastic Film to Cover Corn Silage under Farm Conditions
## 2 Materials and Methods
### Crop and Ensiling Procedure  
A corn hybrid (P1547, Pioneer Hi-Bred Italia Srl, Gadesco Pieve Delmona, Cremona, Italy) was sown in April, at an intended planting density of 75,000 seeds/ha, in an experimental field of about 3 ha. The experimental field received 100 kg/ha K\({}_{2}\)O (as potassium chloride) before sowing, 39 and 100 kg/ha of N and P\({}_{2}\)O\({}_{5}\) (as diammonium phosphate) at sowing and 120 kg/ha N, as urea, at the six leaf stage. The crop was irrigated twice during the growing season. Weed control was performed utilizing mesotrione (0.15 kg AI/ha), S-metolachlor (1.25 kg AI/ha) and terbuthylazine (0.75 kg AI/ha) (Lumax(r), Syngenta Crop Protection S.p.A., Milan, Italy). Corn was harvested at around the 75% milk-line stage and with a DM content of 409 g DM/kg of fresh forage. The forage was chopped, using a self propelled forage harvester (Claas Jaguar 950, equipped with an 8-row Orbis head, Claas, Harsewinkel, Germany), to a theoretical 10-mm length of cut, and ensiled within 2 hours in drive-over piles. Each pile contained around 4 t of fresh forage and was 6 meters long, 3 meters wide and 1 m high at the top of the pile. The experiment was organized in a 3 (plastic films) \(\times\) 5 (times of conservation) factorial treatment arrangement, with two drive-over experimental piles per treatment (for a total of 30 experimental piles). The three sealing materials were: (a) a single 200 \(\upmu\)m thick (6 m wide) black-on-white polyethylene, UV protected film (**PE**); (b) a single 130 \(\upmu\)m thick (6 m wide) black-on-white co-extruded polyethylene-special grade EVOH (SoarnoL\({}^{\text{TM}}\) SG611B, Nippon Gohsei, Osaka, Japan) UV protected film, with a high oxygen barrier (**OB**); (c) a single 120 \(\upmu\)m thick (4 m wide), transparent milky Mater-Bi\({}^{\textregisteredregistered}\) (Novamont SpA, Novara, Italy) biodegradable plastic film (**MB**). The oxygen permeability of the films, determined on the basis of the American Society for Testing and Materials' (ASTM) standard method D 3985-81 ([PERSON] et al., 2018), at 1 bar, at 23 \({}^{\circ}\)C and at 90% relative humidity (RH), was 1196, 9, and 483 cm\({}^{3}\)/m\({}^{2}\) per 24 h for PE, OB and MB, respectively. The water vapor transmission rate (WVTR), determined on the basis of ASTM F1249-06 ([PERSON] et al., 2018), was 1.05 g/m\({}^{2}\), 1.6 g m\({}^{-2}\), and 17.4 gm\({}^{2}\) (per 24 h at 38 \({}^{\circ}\)C and 90% RH) for PE, OB and MB, respectively. Each pile was covered with a PE (10 piles), an OB (10 piles) or an MB film (10 piles). The plastic sheets were held in place by putting gravel all around the silage. Two silos were opened for each treatment after 21, 85, 133, 195 and 230 d of conservation. Furthermore, the effect of the distance from the plastic film was assessed in silage stored in two zones of the silo: close to the film, from 0 to 300 mm (**CF**), and deeper, that is, from 600 to 900 mm (**FF**). This resulted in six treatments: close to the polyethylene film (**PE-CF**), at a distance from the polyethylene film (**PE-FF**), close to the oxygen barrier film (**OB-CF**), at a distance from the oxygen barrier film (**OB-FF**), close to the biodegradable film (**MB-CF**) and at a distance from the biodegradable film (**MB-FF**). Two independent samples (of about ten kilograms of fresh weight) were sampled at each location and for each pile, for a total of four samples per treatment and per opening date. After sampling, the silages were subjected to an aerobic stability test by monitoring the temperature increases due to the microbial activity of the samples exposed to air. About three kilograms of each sample was allowed to aerobically deteriorate at room temperature (20 \(\pm\) 1.0 \({}^{\circ}\)C) in 17 L polystyrene boxes (290 mm diameter and 260 mm height). A single layer of aluminum foil was placed over each box to prevent drying and dust contamination, but also to allow the air to penetrate. The temperatures of the room and of the silage were measured hourly by a data logger.