Water footprint and water productivity analysis of an alternative organic mulching technology for irrigated agriculture

Agriculture is causing unprecedented pressure on water resources to meet a growing food demand. This determines the necessity of implementing innovative, sustainable, and measurable systems to improve water use efficiency while increasing crop yield. This study tested the use of biodegradable mulching (BM) film for irrigated lettuce and the FAO AquaCrop model was used to simulate a precision irrigation scheme. The trials were conducted in the middle Arno River Valley, Tuscany, in Farm 1 (F1) and Farm 2 (F2) during the cropping seasons 2021 and 2022. In 2021 the BM film was tested in late spring at F1 and mid-summer at F2. In 2022, BM was tested twice at F2, in July and September, and once at F1, in June. The AquaCrop model was used only for the F2 mid-summer lettuce trial. Water Productivity (WP_i) and ISO 14046 Water Footprint (WF) were measured, and a correlation analysis was performed. The study's outcome reported larger lettuce plants in the F2 BM July trial (0.806 kg plant^-1) and smaller ones in F1 trial (0.100 kg plant^-1), where the plant density was higher. The amount of irrigation water required was reduced in all the BM trials, ranging between 8%-50%, with the best performance in the F2 BM September trial where the amount was halved. In general, WF was always reduced in the BM trials and the best performance was with the F2 BM July trial (0.13 m³kg^-1). Moreover, F2 indirect WF for the BM film production has a major share of impact on water resources ranging from 0.07 m³kg^-1 to 0.17 m³kg^-1. The best WP was also reached by F2 BM September trial (40.8 kg m^-3). The Pearson coefficient (r) reported a strong negative correlation between WF and WP (-.73, p = .01), while, the determination coefficient ( R²) was 0.545. Hence, is confirmed how the reduction of WF is followed by the rise of WP. However, the low R² shows how the two indicators are not specular but arrays of different useful information. Finally, AquaCrop simulation measured a fall in irrigation requirement (-86%, - 95%) in both treatments, reflecting an overestimation of the farmer irrigation scheme. The results confirmed the positive effect of BM and how using the WF can help farmers track their hotspots on water resources. The production of the BM films presented has a significant impact on water resources due to limited reuse over multiple crop cycles. Longer lasting films should be tested to investigate the reduction of indirect WF.

This study was carried out within the FEASAR-PSR 2014/2020 GO PEI PSGO 40/2017 ORTI BLU fund and the Agritech National Research Center and received funding from the European Union Next-Generation EU (PIANO NAZIONALE DI RIPRESA E RESILIENZA (PNRR) – MISSIONE 4 COMPONENTE 2, INVESTIMENTO 1.4 – D.D.1032 17/06/2022, CN00000022). This manuscript reflects only the authors’ views and opinions, neither the European Union nor the European Commission can be considered responsible for them.