Four-lake watershed, an important agricultural region in Hubei Province of China, is vulnerable to water-logging, using long-term observation to study influence of excessive water in soil on crop has an important significance for prevention of agricultural water-logging disaster and reasonable arrangement of agricultural production. In the study, duration and index of soil moisture excess are put forward and used to describe severity of farmland encountering subsurface water-logging. Based on analysis of 25 years of observational data, the results showed that winter wheat in spring and cotton from seedling to boll stage usually encounter a mild subsurface water-logging; generally subsurface water-logging seldom occurs in boll-opening period of cotton. In terms of typical years' analysis, no subsurface water-logging befell in general drought year, in normal year a phenomena of soil moisture excess doesn't exist in developmental stage of winter wheat and occurs in blossoming and boll-forming stages of cotton, which often leads to a moderate disaster of subsurface water-logging; in general water-logging year, as well as in flood season that annual rainfall is normal, soil water-logging possibly arrives to moderate to severe from cotton seedling to boll-forming stage, so that cotton's nutrient growth and procreation growth are largely affected. Its developmental period could also be lagged due to soil moisture excess for many days and cotton yield therefore would be affected adversely.
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