Research on Controllable Degradation of Novel Sulfonylurea Herbicides in Acidic and Alkaline Soils

The degradation issue of sulfonylurea
(SU) has become one of the
biggest challenges that hamper the development and application of
this class of herbicides, especially in the alkaline soils of northern
China. On the basis of the previous discovery that some substituents
on the fifth position of the benzene ring in Chlorsulfuron could hasten
its degradation rate, apparently in acidic soil, this work on Metsulfuron-methyl
showed more convincing results. Two novel compounds (I-1 and I-2) were designed and synthesized, and they still
retained potent herbicidal activity in tests against both dicotyledons
and monocotyledons. The half-lives of degradation (DT50) assay revealed that I-1 showed an accelerated degradation
rate in acidic soil (pH 5.59). Moreover, we delighted to find that
the degradation rate of I-1 was 9–10-fold faster
than that of Metsulfuron-methyl and Chlorsulfuron when in alkaline
soil (pH 8.46), which has more practical value. This research suggests
that a modified structure that has potent herbicidal activity as well
as accelerated degradation rate could be realized and this approach
may provide a way to improve the residue problem of SUs in farmlands
with alkaline soil.

磺酰脲类（sulfonylurea, SU）除草剂的降解问题已成为阻碍该类除草剂研发与应用的最大挑战之一，在中国北方碱性土壤中这一问题尤为突出。此前研究发现，氯磺隆（Chlorsulfuron）苯环第五位的部分取代基可加快其降解速率，该现象在酸性土壤中较为明显；本研究以甲磺隆（Metsulfuron-methyl）为对象，所得结果更具说服力。本研究设计并合成了两种新型化合物（I-1与I-2），二者对双子叶植物与单子叶植物均保留了优异的除草活性。降解半衰期（DT50）测试结果显示，I-1在pH 5.59的酸性土壤中降解速率有所提升。更令人欣喜的是，在pH 8.46的碱性土壤中，I-1的降解速率较甲磺隆与氯磺隆快9~10倍，这一结果具备更强的实际应用价值。本研究证实，可通过结构修饰获得兼具优异除草活性与快速降解性能的化合物，该策略为解决碱性土壤农田中磺酰脲类除草剂的残留问题提供了可行思路。