Fertilizer enriched bio-based mulch films increase nitrogen and phosphorus availability and stimulate soil microbial biomass and activity

Plastic mulch films are widely used in agriculture to increase crop productivity and to control weeds, but their non-biodegradable nature is causing many negative effects, such as environmental pollution and land degradation. These drawbacks are favoring the development of biodegradable alternatives. Recently, innovative bio-based mulch films composed of carboxymethyl cellulose (CMC), chitosan (CS) and sodium alginate (SA) have been developed. These films have also been enriched with monoammonium phosphate (MAP) to be potentially released during their degradation thus supplying N and P to soil. This study aims to evaluate the impact of N and P enriched bio-based films on N and P pools dynamics and microbial biomass, activity and community structure. For this purpose, two types of films, both with and without MAP-enrichment, were mixed with the soil at 0.1 % (w/w) ratio to simulate field conditions. Soil samples were analyzed at 30, 60, 90 and 120 days after film application to assess changes in above variables. The results showed that MAP-enriched films significantly increased the concentrations of available nitrate and phosphate by up to 76 % and 72 %, respectively. All four film types increased microbial biomass C and N, while enhanced β-glucosidase and N-acetyl-β-d-glucosaminidase activities indicated some biodegradation of CMC and CS. The degradation of the biopolymers was further confirmed by lipase activity, which was on average 79 % higher in the film-amended soils. Moreover, films influenced the microbial community structure, favoring the growth of bacteria, particularly Gram positive, over fungi. Overall, these results suggest that these innovative bio-based films are promising candidates for sustainable agricultural practices.