Changes in vineyard soil parameters after repeated application of organic-inorganic amendments based on spent mushroom substrate.

The changes of physicochemical and biochemical parameters of a silty loam (S1) and sandy loam (S2) vineyard soils added with spent mushroom substrate (SMS) or SMS composted with ophite (OF) as rock dust (SMS + OF) were studied. Two doses of SMS or SMS + OF (25 and 100 Mg ha-1) were applied for two consecutive years (2020-2021) and changes of soil physicochemical parameters, and dehydrogenase activity (DHA), respiration (RES), microbial biomass (BIO), and the phospholipid fatty acids (PLFAs) profile were assayed on a temporal basis. The results showed an increase in soil organic carbon (OC) content, total and mineralised N, P, and K, especially when the highest SMS dose was applied to soils. Repeated application caused OC content over time up to 2.3 times higher than initial content in the silty loam soil. This increase was not observed in sandy soil, possibly due to a higher bioavailability of OC, as indicated by the evolution of extractable humic acid/fulvic acid pools. In both soils, all biochemical parameters increased after amendment, being favoured both by the OC and by the presence of OF. Significant positive correlations were found between DHA, RES and BIO, and OC content especially in the first part and then levelled off after the second dose application. Total bacterial or fungal PLFAs patterns reflected the variation of BIO by SMS application. The higher growth of fungi vs. bacterial community in amended soils was recorded after the first SMS application, although the opposite effect occurred after the second application, with similar results in both soils. The findings indicate that the application of SMS or SMS + OF in vineyard soils could be an appropriate agronomic management practice for maintaining soil sustainability, although doses and application times of these amendments should first be evaluated depending on soil texture.

Field measurement and modelling of chlorotoluron and flufenacet persistence in unamended and amended soils.

The dissipation and persistence of two cereals herbicides, chlorotoluron and flufenacet, were studied in a field experiment including three replicated plots of unamended soil (S), soil amended with spent mushroom substrate (S + SMS), and soil amended with green compost (S + GC), during the winter wheat cultivation campaign. The SMS and GC organic residues were applied to the soil at rates of 140 or 85 t residue ha-1, and herbicides were sprayed as Erturon® and Herold® formulations for chlorotoluron and flufenacet, respectively. Concentrations of both herbicides and of their metabolites were regularly measured in the three soil treatments (0-10 cm) from 0 to 339 days. The dissipation kinetics fitted well the single first order (SFO) model, except that of chlorotoluron that fitted the first order multi-compartment (FOMC) model better in the unamended soil. The dissipation rates of herbicides were lower in amended than in unamended soils. The results also showed that the DT50 of chlorotoluron (66.2-88.0 days) and flufenacet (117-145 days) under field conditions were higher than those previously obtained at laboratory scale highlighting the importance of the changing environmental conditions on the dissipation process. Similarly, the formation of chlorotoluron and flufenacet metabolites under field conditions was different from that previously observed in the laboratory. The performance of the MACRO pesticide fate model, parameterized with laboratory data, was then tested against field data. There was a very good agreement between measured and simulated chlorotoluron residue levels in the three soil treatments, while the ability of the model to reproduce the dissipation of flufenacet was good in the unamended soil and very good in S + SMS and S + GC soils. MACRO might be used to estimate the remaining amounts of herbicides in amended soils from degradation data previously obtained at laboratory scale. This would help to manage herbicide doses in different environmental conditions to preserve the sustainability of agricultural systems.

Previous degradation study of two herbicides to simulate their fate in a sandy loam soil: Effect of the temperature and the organic amendments.

A laboratory study was designed to assess the following: i) the degradation kinetics of chlorotoluron and flufenacet at two different temperatures, 6 °C and 16 °C, in an unamended agricultural soil and one amended with spent mushroom substrate (SMS) and green compost (GC), and ii) the formation of the main metabolites of both herbicides with potential risk for water pollution over degradation time. The aim was to determine the dependence of these herbicide degradations on temperature (Q10 factor) using kinetic parameters, which is essential information for the later simulation of herbicide environmental fate with FOCUS models. SMS and GC were applied in situ to the natural soil as organic amendments at rates of 140 or 85 t residue ha-1, respectively. Unamended and amended soils were taken from the 0-10 cm topsoil of experimental plots (three replicates/treatment) located on an agricultural farm. Samples of soil + herbicides were incubated at 6 °C or 16 °C under laboratory conditions. The degradation curves of chlorotoluron and flufenacet were fitted to single first-order and first-order multicompartment kinetic models, respectively. The flufenacet degradation, the more hydrophobic herbicide, was slower than that of chlorotoluron in all the treatments. The application of the organic amendments to soil increased the half-lives (DT50) for both herbicides incubated at 6 °C (1.3-1.9 times) and 16 °C (1.4-1.9 times) due to their higher sorption and lower bioavailability for degradation in amended soils. The herbicides recorded a faster degradation at 16 °C than at 6 °C (Q10 = 1.9-2.8) due to the increased microbial biomass and/or activity with temperature. The metabolites desmethyl chlorotoluron, flufenacet ESA and flufenacet OA were detected in all the soil treatments at both incubation temperatures. The determination of Q10 factors in amended soils is very valuable for generating accurate input data for pesticide fate models such as FOCUS in order to improve the evaluation of the leaching of herbicides and their transformation products, which is a relevant goal to maintain the sustainability of agricultural systems.