Search

• The influence of meteorological index selection is nonnegligible • The standardized precipitation and evapotranspiration index is generally the best performer. • Relative performances of the indices vary with calculation periods. • The crops are most vulnerable to flooding during their middle growth stages. • Oilseed rape and Anhui were the crop and region most affected by flooding. Flooding is a worldwide destructive disaster that severely restricts agricultural production. Meteorological indices are common tools for regionally assessing the impact of flooding on crop yields, but their performances are rarely compared. In this work, six convenient meteorological indices, namely, precipitation (P), standardized precipitation anomaly (PA), China Z index (CZI), standardized precipitation index (SPI), standardized precipitation and evapotranspiration index (SPEI), and standardized antecedent precipitation and evapotranspiration index (SAPEI), were employed to establish correlations between flooding intensity and crop meteorological yield (FL-Ym correlation). Four major crops in the middle-lower reach of the Yangtze River (cotton, oilseed rape, wheat, and maize) were selected as the study crops. The results indicated that the flooding intensities quantified by the SPI, SPEI, and CZI had strong interconnections, whereas those quantified by the P and SAPEI were less related to the others. In the cases with stronger negative FL-Ym correlations, different indices were more likely to yield consistent identifications. In terms of the districts witnessing significant FL-Ym correlations, in only 26%, 41%, 44%, and 75% of them (respectively corresponding to cotton, wheat, maize, and oilseed rape), the correlations were consistently identified as significant by the majority of the indices, demonstrating the nonnegligible influence of index selection. The relative performances of the examined indices varied with the employed calculation periods (whole growth period and single critical stage), whereas the SPEI was generally the best performer. The SAPEI performed best in assessing the flooding impact during crop critical growth stages, in sharp contrast with its mediocre performance over the whole crop growth period. According to the results of multiple indices, flooding during the middle stages of the study crops exerted the greatest negative impact. Additionally, oilseed rape and Anhui Province were identified as the crop and the region most affected by flooding. This work can provide support for flooding disaster assessment and agricultural water management. [ABSTRACT FROM AUTHOR]

Drought and flood abrupt alternations (DFAA) are new challenges under climate change with particular emphasis on its affects related to agriculture. However, current regional DFAA analysis research rarely investigates agricultural DFAA with special regards to agricultural elements. In this work, a method based on a daily scale index named the standardized antecedent precipitation evapotranspiration index (SAPEI) and crop characteristics was established to investigate the characteristics of agricultural DFAA during cotton growth stages in the middle-and-lower Yangtze River (MLRYR) during 1961–2020. Additionally, the influence of DFAA on cotton climatic yield in response to flooding and drought was examined by multiple regression. The results demonstrate that the SAPEI efficiently described the relations between cotton climatic yield and the intensities of cotton drought and flood and well characterized cotton DFAA events, especially for short-term events. The most recent decade over the past six decades has seen the most frequent cotton DFAA events, and the only significant trend (p < 0.05) of cotton DFAA frequency was an upward trend in Jiangsu Province. In addition, the middle growth stage of cotton was the most DFAA-affected period within a year. Cotton drought-flood alternations (DF) were more common than flood-drought alternations (FD). The most DF-prone and FD-prone regions differed greatly, but the northeastern MLRYR was the most DFAA-prone region. In all provinces, the cotton DFAA frequency was significantly and positively related to the cotton drought frequency. Finally, the relations between cotton climatic yield and the intensities of drought and flood were much less significant in the years with more DFAA events than in other years, indicating an obvious negative interaction between drought and flood in cotton DFAA events. This finding, at the regional scale, confirmed previous field-scale conclusions on cotton responses to DFAA stress. In summary, this work provides references for agricultural water management in adapting to climate change. • A method for assessing agricultural drought and flood abrupt alternation was proposed. • A near-term high risk of cotton drought and flood abrupt alternation was detected. • More droughts probably bring more agricultural drought and flood abrupt alternations. • Negative interaction between cotton drought and flood was found at a regional scale. [ABSTRACT FROM AUTHOR]