Een statistisch onderzoek naar den invloed van het weer op de opbrengst en het gehalte van suikerbieten in Nederland

Correlation coefficients were calculated to examine the relation over the period 1899-1926 between beet yield and sugar content, and rainfall, sunshine and temperature. For every decade and combinations of two or more decades of the period March-October, the correlation coefficient was calculated. The interrelations between the three elements were also considered. The main purpose was to find critical periods as a basis for forecasting yield.There were two critical periods for yield. The sowing period (20 April-20 May) had to be dry. The correlation coefficient with the rainfall was -0.66 ± 0. 11. The month of July had to be warm and bright. (Correlation coefficient for temperature + 0.60 ± 0,12 and for hours of sunshine + 0.66 ± 0.11.)Sugar content was stimulated by a bright dry autumn. Correlation coefficients were for hours of sunshine +0.61±0.12 and for rainfall -0.72 ± 0.09.The main cropping districts Zeeland and Groningen differed strikingly in the correlation coefficient for temperature in August: for Zeeland (south of the Netherlands) +0.27 ± 0.17 and for Groningen (north of the Netherlands) +0.62 ± 0.12.The main regression equation for beet yield was X = M + 761x 2 - 75x 3 . M average yield (kg/ha), x 2 = departure from average temperature (°C) during the last 20 days of July and x 3 = departure from average rainfall (mm) during the period 20 April to 20 May