Agronomy and Horticulture Department


Date of this Version



Published in Physiological Aspects of Crop Yield: Proceedings of a symposium sponsored by the University of Nebraska, the American Society of Agronomy, and the Crop Science Society of America, and held at the University of Nebraska, Lincoln, Nebr., January 20-24, 1969. Edited by Jerry D. Eastin, F. A. Haskins, C. Y. Sullivan, C. H. M. Van Bavel, and Richard C. Dinauer (Madison, Wisconsin: American Society of Agronomy & Crop Science Society of America, 1969). Copyright © 1969 American Society of Agronomy & Crop Science Society of America. Used by permission.


My role in this chapter on environmental manipulations is making a prediction that can be used until experiments render the final verdict.
In chapters preceding mine, an array of physical and physiological phenomena for affecting yield has been laid before the grower of plants. Predicting whether environmental manipulation will increase yield requires that all of these phenomena be considered for foreign lands are littered with the bleaching bones of immigrant varieties and practices that were ambushed by an unsuspected environmental difference.
Interaction is the Scylla of biologic prediction. Formerly we predicted by drawing a curve or writing a formula relating yield to some factor. We used this although common sense told us that the rock of some limiting factor would surely sink us. We simply couldn't accommodate all the factors that common sense told us would be important. For example, we knew light and CO2 would alter the relation between ventilation and yield, but considering them was beyond our capacity.
Now, however, high-speed and capacious information machines give more latitude to our common sense by permitting us to include things that formerly had to be discarded in simplification. The empirical curve is easily replaced by a simulator that not only produces a prediction but also, in its interior, works like the crop. The degree to which it works like the crop is always imperfect, but passages toward realism are now easily found, and more reefs of interaction missed. Light and CO2 , for example, can now be considered in predicting the the effect of ventilation upon yield.