ECOLOGICAL REACTION OF CROP YIELDS 339 



parameters and the proper function of each parameter should be deter- 

 mined. To find the functions of the parameters, often a reverse reasoning 

 will as well be valuable. The object in that case is, given the yield and the 

 growth equation, to construct the function of the combined ecological 

 parameters in such a way that the observations fit well in the growth 

 equation. The observation that the combination of functions of the 

 parameter produces a relation similar to the simple growth equation, shows 

 that the solution arrived at cannot be far from correct. In this way an 

 insight into the interaction and the activity function of the parameters may 

 be obtained. 



