The agricultural value of rainfall in the tropics

The objective of the investigation which is here described was, in the first instance, economic. Having assumed responsibility for the official forecasts of the main crops of the United Provinces, India, it appeared to the writer that, in a country where rainfall so dominated tire agricultural conditions, it should be possible to evolve some system, based upon rainfall data, of forecasting both area and yield of crops whih would be free from dependence on the very doubtful personal equation involved in the methods then in force. The considerable measure of success achieved in forecasting areas led to an attempt to forecast fields—a much more difficult problem. As the work proceeded the method assumed a wider significance bearing on the general problem of the availability of soil moisture for plant growth. In a year's growth, whether this be from a seed or a freshly planted slip, the yield, in whatever form it be measured, is the summation of the various reactions of the plant to its environment at every stage of its growth; in the case of annuals it may even, as Hooker (8) has suggested, include the reaction of the parent plant. What applies to the sum must,a fortiori , apply to the component parts; and it would appear, therefore, that the method employed to evaluate rainfall should afford a means of interpreting the physiological processes of the growing plant, in so far as these are dependent on rainfall.