Gordon Johnson, Extension Vegetable & Fruit Specialist; gcjohn@udel.edu
Currently plastic mulch and drip tape is removed by hand at the end of the growing season and that plastic currently goes into landfills at a cost. Methods to collect and recycle the plastic have been studied. Baling mulch is feasible but recycling of baled mulch has been limited to date by the lack of recyclers willing to accept the mulch and the economics of recycling. An alternative to standard plastic mulches is degradable mulch that can be left in the field to disintegrate. This would reduce the need for recycling or for disposal in landfills and would leave only the drip tape to dispose of (tape collection is also more easily mechanized with tape winders).
Degradable mulches have been studied since the 1980s. Photodegradable mulches left too much plastic residue in the soil (especially where soil covered bed edges) and were not adopted in the region. Paper mulches were difficult to lay and were prone to tearing so they have received limited use. Biodegradable plastics based on plant starches have been studied starting in the 1970s. Oxo-biodegradable mulches use additives to plastic resins to start degradation also have been tested for several decades. However, biodegradable mulch films with acceptable longevity and physical properties were not available until the last decade. Advances have been made to improve the performance of these mulches and field performance has been shown to be acceptable in a number of studies in the US. However, the cost of these mulches is higher.
Research at the University of Delaware in 2012 showed that biodegradable mulch could be used successfully in watermelon production. The BioTelo biodegradable mulch, a corn starch plastic, gave similar yields to standard plastic. However, it was shown to be more difficult to lay, started to tear and breakdown quickly, and was not favored by growers. The Eco-one oxo-biodegradable mulch gave similar performance as standard plastic mulch in application and in crop response. Growers viewed the product favorably.
Newer generation biodegradable plastic mulches have promise for use in vegetable production. Potential problems encountered were similar to those with past products: difficulty in laying the mulch in one product, (BioTelo), short longevity and tearing in that same product, and some residual in the soil for the Eco-one product. Costs were high for BioTelo when compared to standard black plastic mulch and was not fully offset when taking into account labor and disposal costs for standard plastic mulch in comparisons. Eco-one was comparable in cost to black plastic mulch when labor and disposal costs were considered.
Some management guidelines for successful use of biodegradable mulches:
1) Avoid excess tension when laying.
2) Plant immediately after laying.
3) Do not store for a second season’s use, lay entire rolls at one time.
4) Avoid transplanting at mid-day in higher temperatures.
5) Adjust the tension wheels on the plastic layer so they do not nick the mulch. Nicks can turn into long tears.
6) Use with crops that put on a lot of foliage and shade the soil early.