Transport of 14C-prosulfocarb through soil columns under different amendment, herbicide incubation and irrigation regimes

The role of biochar and green compost amendments in the adsorption, leaching, and degradation of sulfamethoxazole in basic soil

The fate of the antibiotic sulfamethoxazole in amended soils remains unclear, moreover in basic soils. This work aimed to assess the adsorption, leaching, and biodegradation of sulfamethoxazole in unamended and biochar from holm oak pruning (BC)- and green compost from urban pruning (CG)-amended basic soil. Adsorption properties of the organic amendments and soil were determined by adsorption isotherms of sulfamethoxazole. The leachability of this antibiotic from unamended (Soil) and BC- (Soil + BC) and GC- (Soil + GC) amended soil was determined by leaching columns using water as solvent up to 250 mL. Finally, Soil, Soil + BC, and Soil + GC were spiked with sulfamethoxazole and incubated for 42 days. The degradation rate and microbial activity were periodically monitored. Adsorption isotherms showed poor adsorption of sulfamethoxazole in unamended basic soil. BC and CG showed good adsorption capacity. Soil + BC and Soil + GC increased the sulfamethoxazole adsorption capacity of the soil. The low sulfamethoxazole adsorption of Soil produced quick and intense sulfamethoxazole leaching. Soil + BC reduced the sulfamethoxazole leaching, unlike to Soil + GC which enhanced it concerning Soil. The pH of adsorption isotherms and leachates indicate that the anion of sulfamethoxazole was the major specie in unamended and amended soil. CG enhanced the microbial activity of the soil and promoted the degradability of sulfamethoxazole. In contrast, the high adsorption and low biostimulation effect of BC in soil reduced the degradation of sulfamethoxazole. The half-life of sulfamethoxazole was 2.6, 6.9, and 11.9 days for Soil + GC, Soil, and Soil + BC, respectively. This work shows the benefits and risks of two organic amendments, BC and GC, for the environmental fate of sulfamethoxazole. The different nature of the organic carbon of the amendments was responsible for the different effects on the soil.

Effect of Organic Residues on Pesticide Behavior in Soils: A Review of Laboratory Research

The management of large volumes of organic residues generated in different livestock, urban, agricultural and industrial activities is a topic of environmental and social interest. The high organic matter content of these residues means that their application as soil organic amendments in agriculture is considered one of the more sustainable options, as it could solve the problem of the accumulation of uncontrolled wastes while improving soil quality and avoiding its irreversible degradation. However, the behavior of pesticides applied to increase crop yields could be modified in the presence of these amendments in the soil. This review article addresses how the adsorption–desorption, dissipation and leaching of pesticides in soils is affected by different organic residues usually applied as organic amendments. Based on the results reported from laboratory studies, the influence on these processes has been evaluated of multiple factors related to organic residues (e.g., origin, nature, composition, rates, and incubation time of the amended soils), pesticides (e.g., with different use, structure, characteristics, and application method), and soils with different physicochemical properties. Future perspectives on this topic are also included for highlighting the need to extend these laboratory studies to field and modelling scale to better assess and predict pesticide fate in amended soil scenarios.

Influence of temperature on the retention, absorption and translocation of fomesafen and imazamox in Euphorbia heterophylla

Climate change will be an additional issue to the challenge to manage herbicide resistant weeds. This work investigated the impact of three temperature regimes (10/5, 20/15 and 30/25 °C) on the efficacy, foliar retention, absorption and translocation of fomesafen, protoporphyrinogen oxidase (PPO) inhibitor, and imazamox, acetolactate synthase (ALS) inhibitor, between two Euphorbia heterophylla populations, one susceptible (S) and one multiple PPO and ALS resistant (R). The R population went from 5 (fomesafen) and 12 (imazamox) times more resistant than the S population at 10/5 °C to more than 100 times to both herbicides at 20/15 and 30/25 °C. Leaf retention of fomesafen was not affected by temperature; however, imazamox retention was less at 10/5 and 20/15 °C than at 30/25 °C, and the R population always retained less imazamox than the S population. ¹⁴C-fomesafen absorption was similar between populations, but lower amounts were absorbed at 10/5 °C regardless of the evaluation time. Recovered ¹⁴C-imazamox rates decreased in both populations as the evaluation time increased, ranging from 82 to 92% at 6 h after treatment (HAT), and from 47 to 76% at 48 HAT, depending on the temperature regime. The ¹⁴C-imazamox losses were greater from 24 HAT in R plants grown at 30/25 °C and in all temperature regimes at 48 HAT. Although both populations translocated large amounts of imazamox, the S population distributed it in the rest of the plant (33%) and roots (15%), while the R population kept it mainly on the treated leaf (24%) or lost ~20% more herbicide than S population at 48 HAT, indicating the need for further studies on root exudation between these populations. Low temperatures reduced resistance levels to fomesafen and imazamox in E. heterophylla, suggesting that temperature influences the expression of the mechanisms that govern this multiple resistance.

Metagenomic analysis reveals mechanisms of atrazine biodegradation promoted by tree species

Metagenomics has provided the discovery of genes and metabolic pathways involved in the degradation of xenobiotics. Some microorganisms can metabolize these compounds, potentiating phytoremediation in association with plant. This study aimed to study the metagenome and the occurrence of atrazine degradation genes in rhizospheric soils of the phytoremediation species Inga striata and Caesalphinea ferrea. The genera of microorganisms predominant in the rhizospheric soils of I. striata and C. ferrea were Mycobacterium, Conexibacter, Bradyrhizobium, Solirubrobacter, Rhodoplanes, Streptomyces, Geothrix, Gaiella, Nitrospira, and Haliangium. The atzD, atzE, and atzF genes were detected in the rhizospheric soils of I. striata and atzE and atzF in the rhizospheric soils of C. ferrea. The rhizodegradation by both tree species accelerates the degradation of atrazine residues, eliminating toxic effects on plants highly sensitive to this herbicide. This is the first report for the species Agrobacterium rhizogenes and Candidatus Muproteobacteria bacterium and Micromonospora genera as atrazine degraders.