Abstract
AbstractBiobased and biodegradable mulches (BDM) are a potentially sustainable alternative to polyethylene plastic mulch because they can be tilled into the soil at the end of the growing season. However, their degradation rate in the soil is uncertain, limiting their on-farm adoption. The objective of this study was to determine whether organic soil management practices could be leveraged to speed degradation of two potentially BDM across two diverse agroecoregions [Lincoln (LNK) and Scottsbluff (SBF), NE, USA]. Management treatments included compost, compost extract, cover crops, all three of these practices combined and a control. The two mulch types studied were a nonwoven polylactic acid fabric with embedded wood particles (PLA), and a starch-polyester mulch film (BLK). Mulches were applied in spring 2017 for vegetable production and removed in fall after harvest. Recovered mulch was sectioned into squares 10 cm2and buried in mesh bags for 22 months. Mulch degradation, and soil chemical, physical and biological properties were measured at four times over 2 years. Management treatments applied seasonally across 2 years led to expected changes in soil properties, yet they had no effect on mulch degradation. Instead, mulch degradation was driven by the interaction of location and mulch type. The BLK mulch had degraded by 98% at LNK after 12 months, but only by half after 22 months at SBF. Degradation of PLA after 22 months was similar between locations with 29 ± 4% mulch mass remaining at SBF and 33 ± 4% remaining at LNK. Climate and soil characteristics at each location were strong determinants of mulch degradation. Specifically, soils at LNK were finer textured, lower in pH, higher in soil water content, organic matter and nitrates, and with greater bacterial abundance compared to SBF. The strong location by mulch type interaction observed could inform the development of regionally specific predictive models of degradation.
Highlights
Agricultural mulch membranes are a cropping system input manufactured from a variety of synthetic or biobased polymers
This study investigated degradation of two potentially biodegradable mulches (BDM) membranes [a nonwoven polylactic acid fabric mulch with embedded wood particles (PLA), and a starch-polyester mulch film (BLK)] under a typical certified organic field vegetable production system across two distinct agroecological zones [Lincoln (LNK) and Scottsbluff (SBF), Nebraska] and different management practices including the use of compost, compost extract, cover crops and a combination of all three of these
BLK mulch was nearly undetectable after 12 months of burial at LNK, but about half of BLK mulch mass remained at SBF after 22 months
Summary
Agricultural mulch membranes are a cropping system input manufactured from a variety of synthetic or biobased polymers. Mulches are widely used in annual specialty crop production systems and are increasingly common in cereal production (Gao et al, 2019). The primary function of mulch is to manage weeds and soil moisture. Additional benefits can include soil warming or cooling, reduced nutrient leaching and disease management (Kasirajan and Ngouajio, 2012). The most widely used mulch is low-density polyethylene film (PE) because it is durable, flexible, low-cost and available in different specifications. The PE mulch films can provide valuable ecosystem services including reduced irrigation requirements, pesticide and fertility inputs, and nutrient leaching (Lippert et al, 1964; Bhella, 1988; Yang et al, 2015)
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