Metabolism of N-[(R)-1-(2,4-dichlorophenyl)ethyl]-2-cyano-3,3-dimethylbutanamide (Delaus, S-2900) and its isomer, N-[(S)-1-(2,4-dichlorophenyl)ethyl]-2-cyano-3,3-dimethylbutanamide (S-2900S), in rats. 1. Identification of metabolites in feces and urine

Rats were orally dosed with a 1:1 diastereomixture of N-[(R)-1-(2,4-dichlorophenyl)ethyl]-2-cyano-3,3-dimethylbutanamide (Delaus, S-2900) and N-[(S)-1-(2,4-dichlorophenyl)ethyl]-2-cyano-3,3-dimethylbutanamide (S-2900S), both labeled with 14C, at 200 mg/kg/day for 5 consecutive days, and 16 metabolites in urine and feces were purified by a combination of several chromatographic techniques. The chemical structures of all isolated metabolites were identified by spectroanalyses (NMR and MS). Several of them were unique decyanated and/or cyclic compounds (lactone, imide, cyclic amide, cyclic imino ether forms). Major biotransformation reactions of the mixture of S-2900 and S-2900S in rats are proposed on the basis of the metabolites identified in this study.     

Microbial mineralization of humic acid-3,4-dichloroaniline complexes

3,4-Dichloroaniline (DCA), a biodegradation intermediate of numerous herbicides, binds covalently to soil humus to form persistent complexes. Prompted by the possibility that, upon repeated treatments, xenobiotic residues may accumulate in humus, the turnover rates of intact, solvent-extracted, and hydrolyzed humic complexes of ¹⁴C-DCA were compared with that of similarly-treated soil organic matter fractions. The turnover rate of intact humic-DCA complexes was considerably faster than the average turnover of soil organic matter. Humic-DCA complexes, that had been washed in solvents to remove adsorbed DCA or hydrolyzed to break susceptible chemical bonds, had turnover rates that were equal to or slower than that of the average soil organic matter, respectively. However, the turnover rates of the solvent-washed and hydrolyzed humic-DCA complexes were similar to that of identically-treated humic acid. The evidence indicates that an extensive accumulation of DCA or similar herbicide-derived halogenated anilines in soil organic matter is unlikely.     

N-(2-bromophenyl)-2-(4,6-dimethoxypyrimidin-2-yloxy)benzylamine, a new selective postemergent herbicide for weed control in winter oilseed rape

N-(2-Bromophenyl)-2-(4,6-dimethoxypyrimidin-2-yloxy)benzylamine is a highly active herbicide, which belongs to a novel class of chemistry. The compound is de novo synthesized in good yield, and the structure is confirmed by (1)H NMR, IR, MS, microanalysis, and X-ray. Its herbicidal activity is assessed under greenhouse conditions. It is effective against many grass weed species, as well as broadleaf weeds, under greenhouse conditions. Field trials indicate that it controls major weeds with a good tolerance on oilseed rape by postemergence application at rates of 15-90 g of active ingredient/ha. This compound possesses low mammalian toxicity and favorable environmental profile. These results suggest that the compound has potential as a new selective postemergent herbicide in winter oilseed rape.     

Microbial dynamics after adding bovine manure effluent together with a nitrification inhibitor (3,4 DMPP) in a microcosm experiment

The application of animal manure effluents in agriculture in combination with nitrification inhibitors should be beneficial for nutrient recycling, soil quality, plant productivity, and greenhouse gas emission and offer economic advantages to make them an alternative to conventional fertilizers. The present study aims to estimate the effects of the addition of bovine manure effluent alone or together with a nitrification inhibitor (3,4-dymethylpyrazol-phosphate (3,4 DMPP)) on the microbial community dynamics in a Mediterranean soil in an incubation experiment over 28 days. The application of the bovine manure effluent increased respiration, microbial biomass carbon, fungal and bacterial growth, and enzyme activities and changed the microbial community structure evaluated by the phospholipid fatty acid pattern. Adding the bovine manure effluent together with the nitrification inhibitor, although partly negating the positive effect of the effluent on soil microbial activity, still resulted in higher or similar growth and activity as in the control. Our results indicate that the addition of the nitrification inhibitor 3,4 DMPP together with a bovine manure effluent could be a promising solution to control the animal manure effluent application effects on soil microbiological properties and microbial dynamics, as well as counteracting direct inhibiting effects of 3,4 DMPP on the soil heterotrophic community.     

Dissipation of the herbicide benzofenap (Taipan 300) in a rice field ecosystem

The fate of benzofenap [2-[4-(2,4-dicholoro-m-toluoyl)-1,3-dimethylpyrazol-5-yloxy]-4'-methylacetophenone] applied to flooded rice was studied at two locations in New South Wales (Australia). Solid-phase extraction (SPE) was compared with liquid-liquid extraction (LLE) for the determination of the commercial chemical in water samples. SPE performed well as compared to LLE (84 vs 80%) in irrigation waters. However, at the lower end of the concentration range (3 microg/L), LLE achieved higher recoveries than SPE (72 vs 59%). Rates of dissipation (DT50) from floodwaters and soils were measured. Dissipation of the herbicide from water and soil occurred fairly erratically in both mediums and can be best explained by a first-order decay process. The DT50 value for benzofenap was <1 day in irrigation water due to rapid deposition of the suspension concentrate formulation. The DT50 in surface soil was 44 days. The maximum measured concentration of benzofenap in a rice field floodwater was 39 microg/L, taking approximately 32 days to dissipate to <1 microg/L.     

除草剂和土壤改良剂对热带农业生态系统中微生物生物量动态的影响

The influences of herbicide alone and in combination with the soil amendments with contrasting resource qualities on dynamics of soil microbial biomass C (MBC), N (MBN), and P (MBP) were studied through two annual cycles in rice-wheat-summer fallow crop sequence in a tropical dryland agroecosystem. The experiment included application of herbicide (butachlor) alone or in combination with various soil amendments having equivalent amount of N in the forms of chemical fertilizer, wheat straw, Sesbania aculeata, and farm yard manure (FYM). Soil microbial biomass showed distinct temporal variations in both crop cycles, decreased from vegetative to grain-forming stage, and then increased to maximum at crop maturity stage. Soil MBC was the highest in herbicide + Sesbania aculeata treatment followed by herbicide + FYM, herbicide + wheat straw, herbicide + chemical fertilizer, and herbicide alone treatments in decreasing order during the rice-growing period. During wheat-growing period and summer fallow, soil MBC attained maximum for herbicide + wheat straw treatment whereas herbicide + FYM, herbicide + Sesbania, and herbicide + chemical fertilizer treatments showed similar levels. The overall trend of soil MBN was similar to those of soil MBC and MBP except that soil MBN was higher in herbicide + chemical fertilizer treatment over the herbicide + wheat straw treatment during rice-growing period. In spite of the addition of equivalent amount of N through exogenous soil amendments in combination with the herbicide, soil microbial biomass responded differentially to the treatments. The resource quality of the amendments had more pronounced impact on the dynamics of soil microbial biomass, which may have implications for long-term sustainability of rainfed agroecosystems in dry tropics.     

Toxic reactivity of wheat (Triticum aestivum) plants to herbicide isoproturon

The herbicide isoproturon is widely used for controlling weed/grass in agricultural practice. However, the side effect of isoproturon as contaminants on crops is unknown. In this study, we investigated isoproturon-induced oxidative stress in wheat ( Triticum aestivum). The plants were grown in soils with isoproturon at 0-20 mg/kg and showed negative biological responses. The growth of wheat seedlings with isoproturon was inhibited. Chlorophyll content significantly decreased at the low concentration of isoproturon (2 mg/kg), suggesting that chlorophyll was rather sensitive to isoproturon exposure. The level of thiobarbituric acid reactive substances (TBARS), an indicator of cellular peroxidation, showed an increase, indicating oxidative damage to plants. The isoproturon-induced oxidative stress resulted in a substantial change in activities of the majority of antioxidant enzymes, including superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), and ascorbate peroxidase (APX). Activities of the antioxidant enzymes showed a general increase at low isoproturon concentrations and a decrease at high isoproturon concentrations. Activities of CAT in leaves showed progressive suppression under the isoproturon exposure. Analysis of nondenaturing polyacrylamide gel electrophoresis (PAGE) confirmed these results. We also tested the activity of glutathione S-transferase (GST) and observed the activity stimulated by isoproturon at 2-10 mg/kg.     

Synthesis and antifungal activities of alkyl N-(1,2,3-thiadiazole-4-carbonyl) carbamates and S-alkyl N-(1,2,3-thiadiazole-4-carbonyl) carbamothioates

A series of alkyl N-(1,2,3-thiadiazole-4-carbonyl) carbamates and S-alkyl N-(1,2,3-thiadiazole-4-carbonyl) carbamothioates with unsubstituted or monobrominated straight chain alkyl groups were synthesized and evaluated as fungistatic agents against Gibberella zeae and Alternaria kikuchiana. These compounds showed variable antifungal activities at concentrations of 5 and 50 microg/mL. The results showed that antifungal activities depended on the length of the alkyl chain with the optimal chain length of 6-11 carbons. Carbamic acid, (1,2,3-thiadiazole-4-ylcarbonyl)-, hexyl ester (4) showed a strong fungistatic activity against A. kikuchiana at both concentrations, with 90.7 and 54% growth inhibition at 50 and 5 microg/mL, respectively. Carbamic acid, (1,2,3-thiadiazole-4-ylcarbonyl)-, heptyl ester (5); Carbamic acid, (1,2,3-thiadiazole-4-ylcarbonyl)-, octyl ester (6); and Carbamic acid, (1,2,3-thiadiazole-4-ylcarbonyl)-, undecyl ester (9) showed strong fungistatic activity against G. zeae at both concentrations. Their growth inhibitions against G. zeae at the concentration of 5 microg/mL were 78, 63, and 59%, respectively.     

Degradation of isoxaflutole (balance) herbicide by hypochlorite in tap water

Chlorine has been widely employed for the disinfection of drinking water. Additionally, it has the capacity to oxidize many organic compounds in water. Isoxaflutole (Balance; IXF) belongs to a new class of isoxazole herbicides. Isoxaflutole has a very short soil half-life and rapidly degrades to a stable and phytotoxic metabolite, diketonitrile (DKN). Further degradation of DKN produces a nonbiologically active benzoic acid (BA) metabolite. In experiments using high-performance liquid chromatography-UV spectroscopy (HPLC-UV) and HPLC tandem mass spectrometry (HPLC-MS/MS), DKN was found to rapidly react with hypochlorite in tap water, yielding the BA metabolite as the major end product. One milligram per liter (19 microM) of hypochlorite residue in tap water was able to completely oxidize up to 1600 microg/L (4.45 micromol/L) of DKN. In tap water, the disappearance of IXF was much more rapid than in DI water. As soon as the IXF is hydrolyzed to DKN, the DKN quickly reacts with the OCl(-) to form nonphytotoxic BA. As a result, the herbicide solutions prepared with tap water at 500 microg/L will no longer possess any herbicidal activity after 48 h of storage. However, in agronomic settings, highly concentrated tank solutions (600-800 mg/L) may be prepared with tap water since the conversion of IXF to BA would represent <5% of the herbicide; therefore, any impact on the herbicide efficacy would be negligible. Results of this study show that current chlorination disinfection protocols in municipal water systems would completely eliminate the phytotoxic form of this new herbicide, DKN, from drinking water supplies; yet, farmers can use chlorinated tap water without significant loss of efficacy.     

Stability of stored N-(n-butyl) thiophosphoric triamide (NBPT) treated urea-based fertilizers

ABSTRACT

The effectiveness of N-(n-butyl) thiophosphoric triamide (NBPT) in reducing ammonia volatilization from urea-based fertilizers has been thoroughly investigated. However, the stability of this inhibitor during storage of NBPT treated urea and urea ammonium nitrate (UAN) needs further investigation. We compared ammonia volatilization from NBPT treated urea (360 mg NBPT kg^?1 urea) and UAN (180 mg NBPT L^?1 UAN) that were stored at room temperature for 6, 3 and 0 months. We measured ammonia volatilization with cylindrical chambers fitted with acid-charged discs at five times for 21 d. Total ammonia volatilization (measured as a % of applied nitrogen) was significantly greater in untreated urea and UAN (32% to 33%) than those in NBPT treated urea and UAN (6% to 12%). Reduction of ammonia volatilization was not significantly different among NBPT treated urea (73% to 81%) and UAN (63% to 73%) irrespective of storage time. This implies that farmers can mix their urea-based fertilizers with NBPT formulation 6 months prior to fertilization without compromising the ammonia volatilization reducing property of the NBPT.     

Fluazifop-P-butyl (herbicide) affects richness and structure of soil bacterial communities

Fusilade (fluazifop-P-butyl) is an extensively used herbicide in legumes cropping systems; nevertheless, the extent of its ecological risk remains unknown. The aim of this work is to estimate the impact of this herbicide on some key enzyme activities, namely acid phosphatase, urease and FDA, and the effect on soil bacterial communities in the rhizosphere of pea (Pisum sativum). Acid phosphatase, urease and FDA showed a high decrease following the application of fluazifop-P-butyl mainly at ten-fold field rate. Grain yield was also severely affected at this concentration (−50%). T-RFLP analysis of 16S rDNA revealed a significant effect of fluazifop-P-butyl application on richness and structure of soil bacterial communities. Putative taxonomic assignation of induced TRFs revealed a marked pattern of acidogenic bacteria like as Staphylococcus, Escherichia, Desulfobacter, Clostridium, Paludibacter and other sulfate-reducing bacteria like as Desulfocella halophila and Desulfocurvus vexinensis. These bacteria may participate in the acidogenesis and the production of propionic acid from the fluazifop-P-butyl after hydrolytic cleavage. They are also known to play important roles in the global biogeochemical sulfur cycles. Unfortunately, some potential human pathogens were also stimulated. Moreover, many putative plant-growth-promoting bacteria belonging to the genera Streptomyces and Bacillus were found to be inhibited in the bulk soil and rhizosphere. The fluazifop-P-butyl effect on bacterial diversity was more pronounced in the rhizosphere compared to bulk soil or uncultivated soil which may suggest that a major component of this effect is mediated by the root system.     

快速检测抗除草剂拿捕净基因流的方法初探

实验探讨了快速检测抗除草剂拿捕净（Sethoxydim)基因流的方法，该方法核心是用双氧水和赤霉素（GA3）打破青狗尾草种子的休眠，让其在含适宜剂量的除草剂基质上发芽，在暗处生长4d后仅通过测量种子发芽后的幼芽生长、形态差异即鉴定出抗、感除草剂种子，从而达到快速检测的目的。