IWRA Proceedings

BACKGROUND

• Both water deficit and excess water in soils, arising from drought and flood disasters, can inhibit crop roots from absorbing water and fertilizer, thus affecting crop growth and yield
• Furthermore, due to increasing climate change, the uneven distribution of precipitation within the year facilitates the  occurrence of drought and flood abrupt alternation (DFAA)
• DFAA events occur objectively across the growing period of local crops
• however, their impacts on crop yields differ from those of individual drought and flood stress
• this work provides guidance for monitoring and reducing cotton DFAA disasters by identifying the high-risk regions and periods
• More importantly, by examining the influence of DFAA disasters on cotton responding to drought and flood
• To provide regional-scale evidence for developing comprehensive planning for irrigation and drainage, so as to improve water use efficiency in agriculture.

CONCLUSIONS

• The SAPEI is applicable for simulating cotton drought and flood and is efficient in capturing the effects of drought and flood on cotton yield.

• the SAPEI-based approach well characterized cotton DFAA events, especially capturing numerous short term events (<20 d)

• In the most recent decade over the past six decades, the frequency of cotton DFAA events in the MLRYR, including both cotton DF and FD events, reached a historic high

• the only significant (p < 0.05) trend of cotton DFAA events was found in Jiangsu Province and it was an upward trend

• These results imply a near-term high risk of cotton DFAA disasters in the MLRYR.

• although cotton DF and FD events differed greatly in their high-risk regions, the northeastern MLRYR was considered the most cotton DFAA-prone region

• The early and late growth stages of cotton had relatively low risks of cotton FD and DF, respectively

• the middle growth stage was generally the period most affected by DFAA events. cotton DF events occurred more frequently than FD events

• relations between the cotton DFAA frequency and the drought frequency were very significant and positive in all the areas in the MLRYR, demonstrating that more cotton drought events tend to result in more cotton DFAA events

• effects of drought and flooding on cotton climatic yield were  significantly stronger in the non-DFAA years than in the DFAA years

Hence, at a regional scale, it is confirmed that the occurrence of cotton DFAA can reduce the yield-reducing effects of cotton drought and flood events, which is fairly in accord with previous field experimental reports