Biodegradable Mulch Films Aid in Sweet Corn Production

Many sweet corn growers are using clear plastic (polyethylene) mulch to warm the soil and to advance harvest maturity. The use of clear plastic mulch may also improve seed germination and increase plant stand under cool soil conditions often encountered in the early spring and may improve the yield and quality of sweet corn. A major disadvantage of the use of plastic is the disposal of the plastic at the end of the season.

Recently, biodegradable polymers have been developed for agricultural uses. Biodegradable films often are thinner than traditional polyethylene but otherwise are quite similar. They may be made from renewable resources such as starch, cellulose or degradable polymers. Biodegradable polymer films are degraded by the processes involving sunlight, heat and mechanical stress, eliminating the need for pick-up and disposal at the end of the season. The polymers eventually are converted through microbial activity in the soil to carbon dioxide, water and natural substances. Biodegradable mulches are not the same as the photodegradable mulches that were previously available that left plastic residues in the fields. Formulation of the film determines the life of the mulch.

An experiment was carried out to compare the effects of clear plastic mulch and biodegradable clear polymer mulch films in sweet corn production on soil warming, plant growth, crop maturity, yield and quality, and to document the degradation of the biodegradable polymers under field use. Four biodegradable mulch films (Eco-Film, Cco-one, EcoWorks and Master-Bi) were compared to clear polyethylene and bare soil using a randomized complete block design replicated four times. Mulch was laid April 29, and plots were seeded April 30. The soil was a Fox sandy loam. Cultural practices were similar to those followed by commercial operations in the area.

The Master-Bi mulch film was thinner than the other mulches and required extra care in laying so that it did not tear. Some small holes occurred in the Master-Bi mulch when it was laid. The clear plastic and Eco-one mulch films lasted through the season and were still intact at harvest. The EcoWorks mulch became brittle as the season progressed and tears developed, however, at harvest (81 days after the mulch film was laid), over 90 percent soil cover remained.

Breakdown of the Mater-Bi and EcoFilm started with long slits developing in the mulch at the tassel stage of corn development (approximately 50 days after the mulch was laid). By harvest, multiple tears and holes had developed in the mulch and approximately 25 percent to 50 percent of the soil was exposed. By late September, all biodegradable mulches were sufficiently degraded and after field discing, few pieces of plastic remained and none were larger than 5 inches.

Soil temperature under all mulch films was higher compared to bare soil. Soil temperature under the clear mulches (clear polyethylene and Eco-one) was higher compared to the translucent mulch films (EcoFilm, EcoWorks and Mater-Bi). Corn plant emergence from all mulch films occurred ahead of bare soil. This was due to an increase in soil temperature under the mulches. Corn plant emergence from the clear plastic was ahead of the translucent mulch films (EcoFilm and EcoWorks) 10 days after seeding and was ahead of the EcoWorks mulch 12 days after seeding (Table 1). Again, the differences in plant emergence were due to the differences in soil temperature under the mulches. There was no difference in final plant stand between treatments. Ear silk formation was earlier for all mulch films compared to bare soil. Corn plant height was taller for all mulch films compared to bare soil.

Sweet corn harvest was advanced by approximately three days using the mulch films compared to bare soil (Table 2). Marketable yield was slightly higher and ear size was slightly larger for all mulch films compared to bare soil, although the differences were not statistically significant at the 5 percent level (Table 2). No significant differences in other quality parameters (tip cover, tip fill) occurred between the treatments.

Weed control must be good under the mulch as weeds will grow through the biodegradable films rather than being smothered as often occurs under the stronger polyethylene films.