新型5-二烷基氨基取代磺酰脲类化合物在土壤中的残留监测及其对作物的安全性 (英文)

周 沙, 李佳星, 华学文, 李永红, 刘 斌,陈安良, 陈 杰*,, 李正名*,

(1. 浙江农林大学 林业与生物技术学院，浙江省绿色农药2011协同创新中心，生物农药高效制备浙江省工程实验室，浙江农林大学省部共建亚热带森林培育国家重点实验室，杭州 311300；2. 南开大学 化学学院，元素有机化学国家重点实验室，天津化学化工协同创新中心，天津 300071；3. 聊城大学 农学院，山东 聊城 252000)

Sulfonylurea (SU) herbicides have been widely used in agriculture since the development of chlorsulfuron in 1981[1-2]. Nowadays, chlorsulfuron has been banned by the Ministry of Agriculture and Rural Affairs of the People’s Republic of China for its long persistence in soil[3]that will generate damage to sensitive crops,such as paddy, wheat, corn, bean and cotton[4-7]. Wiese et al. measured chlorsulfuron persistence in field study in Pullman clay loam under “winter wheatsorghum-fallow” 3-year crop rotation pattern with soil pH ＞ 7.5. The residue of chlorsulfuron injured the newly planted sorghum after 25 months with an application of 34 g/hm2on wheat growing[8]. According to the assay conducted by Institute of Plant Protection in Jiangsu Academy of Agricultural Sciences, the seedling emergence of corn, bean and cotton in spring was severely influenced by the application of 15 g/hm2chlorsulfuron in Autumn[9].

Inspired by the commercialization of flupyrsulfuron-methyl[10], iodosulfuron-methyl[11], foramsulfuron[12]and mesosulfuron-methyl[13]with a 5th substituent on the benzene ring, we introduced different kinds of groups onto chlorsulfuron[14-15]. Dimethylamino and diethylamino (synthesized according to our previous procedures[14], Scheme 1) substituted SUs stand out for their high potent herbicidal activity with dramatically accelerated degradation rate in acidic and alkaline soils[14-18].

In order to promote further development of the new compounds, the soil degradation dynamic was monitored byBrassica campestrisvia pot trials in greenhouse (25 ℃ ± 2 ℃). The inhibition rate againstB. campestriswas taken as the safety indicator of these compounds. The corn, sunflower, wheat as well as paddy were sowed when the damage of rape diminished. As for the application of chlorsulfuron in wheat field, the wheat safety was evaluated at high concentrations. In order to assess the potential in other cereal fields, the corn safety was tested meanwhile. These appreciable results can be significantly instructive for the development of novel SU herbicides with controllable degradation rate.

1 Materials and methods

1.1 Experimental materials and instruments

The experimental compounds were systhesized by ourselves in laboratory and all reaction reagents were analytical grade. The experimental materials and instrument were listed as below: rape (Youlv), corn(Xindan 66), sunflower (Kaqi 601), wheat (Jimai 22),paddy (Ning 88), spray tower (3WPSH-00E potter spray tower, Nanjing Institute of Agricultural Mechanization, Ministry of Agriculture and Rural Affairs).

1.2 Experimental method

1.2.1 Degradation dynamic in soil in greenhouse

The soil degradation dynamic of tested compounds was conducted via pot trials in greenhouse (25 ℃ ±2 ℃)[19-20]withB. campestrisas monitor. The soil used was sampled from Cangzhou city in Hebei Province and the physical data about the soil texture, organic matter, pH value, cation exchange capacity (CEC) and mechanical composition which are listed in Table 1 were tested by Tianjin Institute of Agriculture Resource and Environment. The assay was classified into 4 treatments (0: control, 1: Ia, 2: Ib, 3: chlorsulfuron; each compound was dissolved in DMF to prepare 5% mother solution and then diluted with water containing 1‰ of Tween-80 to the required treatment cencentration), and each treatment was triplicated. The experiment was carried out as follows.Preparing 192 pots with potting mix (volume ratio of loam : vermiculite : compost plus = 1 : 1 : 1), the height was kept about four fifth of the flowerpot and the compounds were sprayed onto the soil evenly with the concentration of 60 g/hm2with spray tower and rape was sowed (15 seeds per pot, 4 treatment ×3 replication) every week following with the moisture adjustment until the soil was moist, as well as cultivation. The fresh weight of cover crop was measured after 16 days, and the inhibition rate was calculated to evaluate the degradation dynamic.Afterwards, at the 35 days after compounds treatment,the corn (5 seeds per pot), sunflower (7 seeds per pot),wheat (10 seeds per pot) and paddy (12 seeds per pot)were seeded for evaluation the crop safety (4 treatment × 3 replication) when Ia and Ib degraded extremely faster than chlorsulfuron. The fresh weight was examined, the inhibition rate were evaluated, and the variance analysis of the data was performed by the Duncan multiple comparisons with the SPSS 22.0 software[21].

Table 1 Analysis data of soils

1.2.2 Crop safety assay

Wheat safety test: the wheat was dealt with soil and foliage treatment via pot trials in greenhouse (25 ℃ ±2 ℃)[19-20]. The applied concentration was 15, 30, 60,120 g a.i/hm2, and each treatment was triplicated. In soil treatment, the compounds were sprayed onto the soil in cups (d= 7 cm) following the seeding performance.After that, the moisture was maintained and cultivated in greenhouse. The fresh weight of the cover crop was measured after 22 days, and the crop safety was represented by the inhibition rate. The variance analysis of the data was performed by the Duncan multiple comparisons with the SPSS 22.0 software[21]. In foliage treatment, the seeding was conducted following adjusting the moisture and temperature until the wheat grew to four-leaf stage. The compounds were sprayed individually, and the result was measured after 28 days,the same procedure as soil treatment.

Corn safety test: the corn safety was conducted by soil and foliage treatment as wheat. After soil treatment of the relevant concentration 30, 60, and 120 g a.i/hm2of target compounds in cups (d= 12 cm),the seeding was performed following the moisture and temperature adjustment. The result was determined after 16 days, and variance analysis was proceeded as wheat safety. Whilst in foliage treatment,the corn was treated until the stage of three-leaf period. The result was measured as wheat after 23 days.

2 Results and Discussion

2.1 Degradation dynamic in soil

The sensitiveB. campestriswas taken as indicating crop that their inhibition rate reflects the degradation dynamic in soil of different compounds, as displayed in Fig. 1. The number 0, 1, 2, 3 represents different treatment as control, Ia, Ib and chlorsulfuron from left to right. As time passed by, theB. campestrisrecovered gradually after Ia and Ib treatment while there was still severe damage of chlorsulfuron until the 6thtreatment. From the changing growth ofB.campestris, we can judge that the compounds Ia and Ib degraded extremely faster than chlorsulfuron that the tendency is consistent to the soil degradation in laboratory.

The fresh weight of covered crop was examined,and the statistical analysis of average data was conducted by intra- and inter-treatments comparing with control, showed as Table 2 and Fig. 2. From the data, we can see that the damage caused by Ia was lightening that the inhibition rate decreased from 96.3% to −48.6% when theB. campestriswas seeded after 63 days of compound treatment. Conformably,the inhibition curve of Ib was simillar to Ia. Meanwhile,the inhibition rate was still higher than 70% after 70 days of chlorsulfuron treatment. The serious phytotoxicity resulted from chlorsulfuron indirectly illustrated its long persistence in soil while Ia and Ib inverse. The rapid recovery ofB. campestristreated by Ia and Ib is supposed to be accountable for their dramatically accelerated soil degradation which seems coincident with the regulation in alkaline soil indoors.

According to the data, the inhibition rates after 28 days of compound treatments were 5.8%, 24.8%,96.1%, respectively that Ia and Ib degraded obviously.Afterwards, the corn, sunflower, wheat, paddy were sowed as well asB. campestrisafter 35 days in order to evaluate their crop safety, the results showed in Fig. 3 and Table 3. As can be seen from the photography, chlorsulfuron displayed severe damage to crops except for wheat that there was still persistence in soil. As the table displayed, the inhibition rate of chlorsulfuron to corn, sunflower, paddy was 88.3%,43.6%, 93.8%, respectively which was consistent with photography. Conversely, the negligible inhibition even apparent promotion of Ia and Ib can be seen on corn, sunflower, wheat and paddy that the inhibitionrate was 0.9% and 5.1%, −16.7% and −4.2%, −54.2%and −27.8%, −30.2% and −15.3%, respectively.

Table 2 Inhibition results against B. campestris after compounds treatment

From the inhibition rate against rape, corn, sunflower, wheat and paddy, the compounds Ia and Ib degraded rapidly comparing to chlorsulfuron while it was consistant with the data in laboratory. In consideration of the degradation rate, the electronic effect may be changed by the 5th substituents (dimethylamino and diethylamino) that the substituted compounds were more easy to be degraded not by hydrolysis but also by microbial degradation. The way of degradation and the degradation product can be studied and determined refering to the reported researches[22-24]in the future.

2.2 Crop safety

2.2.1 Wheat safety As for the special application in wheat field of chlorsulfuron, the wheat (Jimai 22)safety of target compounds Ia and Ib was tested by pre- and post-emergence, taking chlorsulfuron as control. As Fig. 4 displayed, the concentration ofcompounds was 120, 60, 30 and 15 g a.i/hm2from left to right that the growth differs each other. As we can see from Table 4, there was serious damage of Ia and Ib under pre-emergence. While in foliage treatment from low to high concentration, the inhibition of Ia was 1.0%, 9.1%, 15.6%, 25.8%, with Ib was 4.6%,12.9%, 19.4%, 36.4%, respectively. At the concentration of 15-30 g a.i/hm2, there was not significant inhibition against wheat of Ia and Ib. Meanwhile, there was no apparent damage observed of chlorsulfuron which is specially applied in wheat field with its inhibition rate as −2.2%, 0.8%, 7.7% and 17.1%.

Table 3 Crop safety after 35 days of Ia, Ib and chlorsulfuron treatments

2.2.2 Corn safety Furthermore, the corn (Xindan 66) safety was conducted by soil and foliage treatment to verify whether the compounds can be used in corn field, as displayed in Table 5. As we can see from the results of pre-emergence, Ia showed negligible damage at 30 g a.i/hm2with its inhibition rate as 19.3%. Meanwhile, the inhibition of Ib can also be delightful with inhibition as 11.2%, 15.4%, 16.1% at 30, 60 and 120 g a.i/hm2. In post-emergence, Ib did not display significant inhibition with its inhibitionrate as 4.0%, 9.7% and 17.0% successively, nor did chlorsulfuron. Surprisingly, Ia exhibited promotion with 5.6%, 7.8%, 3.7% at the dosage of 30, 60 and 120 g a.i/hm2. From the appreciable data, Ia and Ib may be applicable in corn field.

Table 4 Wheat safety of Ia, Ib and chlorsulfuron

Table 5 Corn safety of Ia, Ib and chlorsulfuron

3 Conclusion

In consideration of the practice of dimethylamino and diethylamino substituted SU herbicides Ia and Ib especially for their residue in soil, the degradation dynamic was monitored byB. campestrisin greenhouse.From the growth and inhibition rate ofB. campestris,the phytotoxicity decreased rapidly after 21 days of Ia and Ib treatments. There was negligible inhibition even apparent promotion of Ia and Ib after 28 days while chlorsulfuron still has serious damage on corn,sunflower and paddy. As for the crop safety, there was significant phytotoxicity on wheat under soil treatment while the impact of foliage treatment was moderate. While in corn safety trials, there was not severe damage discovered under both pre- and postemergence that there was even facilitation of Ia at the concentration of 30-120 g a.i/hm2under foliage treatment. These favorable results have made great efforts for further practicable application of Ia and Ib comparing with chlorsulfuron. This method of structure modification can provide valuable information for the development of eco-friendly agrocompounds.