Regularly mown road verges are an important habitat for conservation of grassland vegetation. Disturbance and movement of seed-contaminated soil during road construction and maintenance makes road verges susceptible to the establishment of invasive alien plants such as garden lupine (Lupinus polyphyllus Lindl.). To combat the spread of L. polyphyllus via seeds, we tested methods for seed destruction using heat. This study aimed at developing heat eradication methods for dry and imbibed L. polyphyllus seeds applying dry heat (88, 93, 98, 103 C for 1, 3, 5, 10 min) in a laboratory, steam (85, 90, 95 C for 3, 5, 10 min) in a test box steaming device, and (97 C at 10 to 17 min; dry seeds only) in a stationary soil-steaming machine (S30). To speed up water absorption and posttreatment germination, the imbibed seeds were manually scarified before the heat treatment and the dry seeds afterward. Additionally, germination of two seed batches of different ages was tested applying dry heat (88, 98 C at 3, 5 min). Steam treatments inhibited seed germination more than dry heat in both dry and imbibed seeds. Germination dropped to <5% when steamed at ≥90 C or dry heated at >100 C. Seed germination decreased with higher temperatures and longer exposure times. Imbibed seeds exhibited lower germination compared with dry seeds for dry and steam heat. Approximately 0.5% of dry seeds germinated when steamed using the S30. The seeds collected in 2022 were less sensitive to dry heat than seeds from 2020. In conclusion, hot steam is more effective in reducing L. polyphyllus seed germination than dry heat. Thus, to successfully eradicate L. polyphyllus seeds in soil masses, we recommend steaming them at 97 C for at least 10 min.

The concentration of fluridone {1-methyl-3-phenyl-5-[3-(trifluoromethyl)phenyl]-4(1H)-pyridinone} residue in Miller clay and Lufkin fine sandy loam was determined at various intervals following incorporated and nonincorporated applications in the field. Low levels of fluridone were present in Miller clay after 250 days while up to 25% remained in Lufkin fine sandy loam 385 days after treatment. Incorporation of fluridone increased its persistence in, Lufkin fine sandy loam but not in Miller clay. Fluridone degradation in Miller clay and Lufkin fine sandy loam was more rapid in the field than under controlled conditions. Fluridone degradation in sterilized Brennan fine sandy loam and Hidalgo sandy clay loam was significantly slower than in nonsterilized soil kept under the same conditions. These differences were not observed in Lufkin fine sandy loam and Miller clay.

A sequential extraction procedure was developed to study the fate of pendimethalin [N- (1 -ethylpropyl) -3,4- dimethyl - 2,6 - dinitrobenzenamine], trifluralin (α,α,α -trifluoro - 2,6 - dinitro - N,N - dipropyl - p - toluidine), and oryzalin (3,5 -dinitro-N4,N4 -dipropylsulfanilamide) in soil over a 6 - month laboratory incubation period. The distinction of non - bound residues was based on an acidic - methanol extraction followed by an extraction with an acetone :H2O : HCl (95:4:1, v/v/v) solution and then extraction with 0.5 N NaOH with further fractionation of the NaOH extract by partial precipitation. After 6 months, soil - bound 14C-residues of pendimethalin, trifluralin, and oryzalin contained 15, 14, and 23%, respectively, of the radioactivity applied to non - sterilized soil. The proportion of bound radioactivity associated with each organic fraction was nearly identical for each herbicide; 46, 12, 12, and 30% was associated with the acetone:H2O:HCl-soluble, fulvic acid, humic acid, and humin organic fractions, respectively. Soil sterilization reduced herbicide degradation by 31% and radioactivity in the fulvic acid, humic acid, and humin organic fractions by approximately 50% during the 6-month period. Radioactivity in the acetone:H2O:HC1-soluble fraction was reduced less than 10% by soil sterilization.

Greenhouse and laboratory experiments were conducted on common waterhemp and soil collected from 131 soybean fields in Missouri that contained late-season common waterhemp escapes. The objectives of these experiments were to determine the effects of soil sterilization on glyphosate-resistant (GR) and -susceptible (GS) common waterhemp survival, to determine the effects of soil sterilization and glyphosate treatment on infection of GR and GS common waterhemp biotypes by Fusarium spp., and to determine the soil microbial abundance and diversity in soils collected from soybean fields with differences in common waterhemp biotypes and herbicide and crop rotation histories. Common waterhemp biotypes were treated with 1.7 kg glyphosate ae ha−1 or left untreated once plants reached approximately 15 cm in height. Common waterhemp survival was visually assessed at 21 d after glyphosate treatment (21 DAT). To determine Fusarium infection frequency, a single intact common waterhemp root was harvested from each treatment at 0, 3, 7, 14, and 21 DAT and surface sterilized, and 10 to 15–mm common waterhemp root sections were plated on Komada culture medium. After 14 d incubation, fungal colonies were selected from colonized roots and maintained on potato dextrose agar medium amended with antibiotics before identification. Speciation of Fusarium isolates was conducted through microscopic examination of fungal characters and confirmed by sequencing and analysis of ribosomal DNA. Soil samples from 131 different collections were subjected to phospholipid fatty acid (PLFA) analysis and were conducted utilizing gas chromatography to determine the soil microbial community abundance and structure. Common waterhemp plants grown in sterile soils had the highest common waterhemp survival, regardless of biotype. After treatment with glyphosate, survival of GS common waterhemp grown in nonsterile soil was only 29% 21 DAT, whereas survival of GS common waterhemp grown in nonsterile soil was only 10%. Similarly, GR common waterhemp survival was reduced from 83 to 61% following treatment with glyphosate when grown in nonsterile compared to sterile soil. Fusarium spp. were recovered from only 12% of the assayed roots (223 treatments with Fusarium out of a total 1,920 treatments). The greatest occurrence of Fusarium root infection in both GR and GS common waterhemp occurred in nonsterile soils following a glyphosate treatment. Few differences in total PLFA were observed in field soil collected from locations with either GR or GS common waterhemp, and regardless of herbicide or crop history. This research supports previous findings that plant species are more sensitive to glyphosate in nonsterile than sterile soils and indicates glyphosate may predispose plants to soil-borne phytopathogens. This research also suggests that continuous use of glyphosate does not significantly affect soil microbial abundance or diversity.