Sadon riippuvaisuus väkilannoituksen ja kesän lämpöolojen vaihteluista Suomessa: Regressioanalyyttinen tarkastelu

Authors

• Auvo Kiiskinen Taloudellinen tutkimuskeskus, Helsinki

DOI: https://doi.org/10.23986/afsci.71427

Abstract

In Finnish agriculture the postwar years have shown a marked decrease in the development of the average yield per hectare, as compared with the trend in the prewar period. Between the five-year periods 1921—25 and 1935—39, the yield per hectare increased more than 27 per cent, the equivalent increase from the latter period to 1950—54 being only one per cent. This slow increase in the yield is all the more notable when we consider that the quantities of fertilization at the same time rose by 380 per cent per hectare while the increase during the last decade before the war was only 40 per cent. The present study tries to point out the effects of the changes in temperature on this yield development. The earlier studies – which have dealt with the dependency of the yield upon climatic factors in Finland – have shown that the condition of temperature is the factor to which the yields in our circumstances are correlated most closely. In addition to the average temperature in May—August, the volume of fertilization was taken as a second explanatory variable. The partial correlation coefficient between the fertilization volume and the average yield showed during the periods of 1921—39 and 1948—54 a value r12∙3 = 0.76, while the corresponding value of the temperature and yield was r13∙2 = 0.65. The coefficient of the multiple correlation was R1∙23 = 0.82. By using the regression analysis it was found that the coefficient of determination rose when describing the dependency of the yield on the explantory variables in question by an exponential function. Sh = aX1 b2 ∙ X2 b2 ; Sh = volume of the yield per hectare X1 = quantity of fertilization input per hectare X2 = average temperature of May—August a1, b1, b2 = parameters. By the method of the least squares the elasticity coefficients b1 and b2 appeared to be; b1 = 0.097 ± 0.011 and b2 = 0.647 ± 0.121. These elasticities do not give a true picture about the relative explanatory abilities of the two variables because their standard deviations are quite different. The values of the beta-coefficients are in this case respectively 0.76 and 0.47. The coefficient of multiple correlation of the model is R = 0.90. The model is illustrated by a diagram on page 214. The analysis points out the notable economic effects of the changes in temperature in Finnish agriculture. The fact that the average temperature of the summers during 1948—54 remained about 1.2 C° lower than during 1934—39, seems, according to the study, broadly speaking to have eliminated the effect of the big increase in the fertilization volume and the effects of the agricultural advancement.