Growth and yield in wheat, oats, flax, and corn as related to environment

Growth curves and data on yields of wheat, oats, flax, and corn, together with weight per 1,000 kernels of wheat, oats, and flax during a period of four years, 1934-1937, are presented. Temperature and precipitation data and graphs of soil moisture in the plats on which these crops were grown are presented. Methods employed in this study are described in detail. The period of investigation is too short to warrant a statistical analysis or definite conclusions. Certain tendencies may be observed as follows: (a) In wheat there is a positive and fairly consistent association between weight of straw and yield of grain when the four years' data are considered. The association is much less apparent in oats and flax. (b) Weight per 1,000 kernels is associated rather directly with yield of oats grain and to a less extent in flax. The association is much less apparent in wheat. (c) The number of seeds per boll is associated directly with yield of flax seed, but the association between number of kernels per spike and yield of wheat grain is not apparent. (d) Associations of yield with precipitation may be more apparent than real since the temperature factor is important. (e) In corn there appears to be no association of yield of forage with rainfall and not uniformly with height. Measurement of several individual plants present some important advantages over mass samples, as follows: (a) Comparison of individuals in growth, yield, and disease can be made. (b) Individuals accidentally injured or killed are easily detected and eliminated from consideration. (c) Variation due to individual differences may be measured and used for determination of this error. (d) Individuals may be selected in areas of full stand and free from weeds, ant hills, animal droppings, etc. (e) The same samples may be used for each determination. The available soil moisture offers a single factor which represents a resultant of various elements of environment. In 1936, growth continued in wheat after soil moisture at all depths sampled had been reduced below the computed wilting coefficient. In oats, flax, and corn growth continued after soil moisture at one or two depths had been so reduced.