2019 ASHS Annual Conference

Biodegradable mulches (BDMs) provide many of the benefits of polyethylene mulch (PE), without the disposal issues of PE. BDMs are tilled into the soil at the end of the growing season, breaking down to CO₂, water and microbial biomass. Various attempts have been made to monitor degradation of BDM macro-fragments in the soil, and thus far, these methods have been time consuming and inaccurate. No quick assessment method is available to growers and researchers to monitor and quantify BDM degradation. This study took place in conjunction with experiments growing pumpkin (2015-2016) on four black BDM (OrganixAG, NatuRecycle, BioAgri/Bio360, and PLA-PHA), black PE mulch, brown cellulose (WeedGuardPlus (WGP)) mulch and bareground treatments. In 2017-2018, pepper was grown in the same field and all mulches were the same with the addition of a white-on-black (WOB) BDM treatment. In all years of the study, BDMs and cellulose mulch were tilled into the soil in the same plot locations at season’s end. We assessed a simple method using a meter-squared PVC quadrat tossed randomly on the bed within a day after tillage, then counting and estimating the area of mulch fragments recovered on the soil surface in both spring and fall of 2016, 2017 and 2018. As expected, more fragments were recovered in fall directly after tilling mulches into the soil. An increase in fragment recovery in fall 2016 versus 2017 was likely due to drought in 2016 slowing degradation. Moreover, the spike in mulch recovery in fall 2018 in Organix, PLA-PHA, and WOB likely was caused by extreme nutsedge pressure, which lifted the mulch and prevented mulch-soil contact, as well as more exposure of the mulches to UV rays, due to heat-induced plant stunting directly after 2018 planting. Spring mulch fragment recovery was under 100 cm²/m²for all treatments, except for PLA-PHA in spring 2018. This increase in PLA-PHA fragment recovery may be due to increased brittleness of the mulch roll as the study progressed. The WOB BDM treatment was added in 2017, and, therefore, only tilled in two seasons. Thus far, the WOB seems to be degrading comparably to black BDMs. PE, bareground and WGP plots were almost completely free of mulch fragments, which gives an estimate of washing or blowing of fragments from plot-to-plot. In conclusion, the data show that this method is a quick and easy way to monitor BDM degradation in the field from year to year.