A TWO-FACTOR SYSTEMATIC DESIGN FOR FERTILIZER STUDIES

Abstract

N and P fertilizers were applied at increasing rates in alternating directions crossed over (IRADCO) at right angles upon each other. One fertilizer was applied so that, in the contiguous strips, the rates increased in alternate directions. The second fertilizer was applied similarly but at right angles to and on top of the first fertilizer. This arrangement with the increasing-rate spreader available allowed 162 combinations of the two fertilizer elements in duplicate in each block. Two such blocks set at right angles to each other were considered to offer reasonable control of possible fertility gradients in the field. The main value of the design is that many fertilizer levels for the establishment of yield response surface functions can be acquired with less effort and in a fraction of the area required with plots of conventional size. The form of the yield response to fertilizer was adequately represented by regression models fitted to the data. The IRADCO design, involving both the field technique and regression modelling, can be used to determine the response to fertilizer levels by various crops at several locations.