Performance of the standardised precipitation evapotranspiration index at various lags for agricultural drought risk assessment in the Czech Republic

Abstract In this study we investigated the influence of drought on crop productivity and, in particular, the drought time-scales that affect the growth of eleven agricultural crops with growth cycles of different lengths in the Czech Republic. In addition, the performance of the standardised precipitation evapotranspiration index (SPEI) at various lags for the assessment of agricultural drought risks was determined. The SPEI was used to quantify the drought (wet) conditions for each month of the year and 24 accumulated lags for 304 climatological stations from 1961 to 2012. The temporal evolution of the standardised yield residuals series (SYRS) of 11 agricultural crops (spring wheat, winter wheat, spring barley, winter barley, winter rye, oats, oilseed rape, maize, sugar beet, potatoes, and grapevine) over a period of 52 years were conducted. To summarise the correlation analyses and compare the drought effect among crops, we found differences in the responses of agricultural crops to different lags of the SPEI. However, the monthly de-trended SPEI had a relatively strong association with SYRS at critical growth stages of the crops. The greatest yield-drought correlation was for cereals ( r  = 0.52–0.60; May–June), and the least yield-drought correlation was for grapes ( r =  0.31; early flowering and berry growth). If one compares the frequency of drought between 1961–1980 and 2001–2012, it is evident that over the past 12 years, the drought risk in the April–June period has increased by more than one fold. Drought during the April–June period became a factor explaining a considerable proportion of the yield variability. We found that drought risk expressed in terms of the SPEI at 1-, 3-, and 6-month lags is an increasing problem during the early stages of root and tuber crops.