THE INFLUENCE OF FERTILIZER PLACEMENT AND RATE OF NITROGEN ON FERTILIZER PHOSPHORUS UTILIZATION BY OATS AS STUDIED USING A CENTRAL COMPOSITE DESIGN

Abstract

A greenhouse study was conducted to determine the optimum fertilizer phosphorus placement for oats and to determine the influence of nitrogen rate on the absorption of fertilizer phosphorus. A central composite design in three variables was used to permit the development of quadratic equations to express the response criteria as functions of the placement variables — horizontal distance and depth from the seed — and rate of nitrogen.The fertilizer phosphorus absorption was determined at four stages of growth, the last stage being 58 days after planting. The dry weight of tops, total phosphorus content and per cent of the phosphorus derived from the fertilizer were determined at the completion of the experiment 58 days after planting.At the 14-day stage fertilizer phosphorus absorption was greatest from fertilizer placed with the seed but, at the 28- and 42-day stages, was greatest from fertilizer placed 1 inch to the side and 2 or 3 inches below the seed. At the 58-day stage, fertilizer placed with the seed resulted in the greatest absorption of fertilizer phosphorus. The influence of placement on the per cent of the plant phosphorus that was derived from the fertilizer was similar to that on fertilizer phosphorus absorption.Nitrogen increased fertilizer phosphorus absorption at all but the 14-day stage, increased plant weight to a lesser extent and decreased the per cent phosphorus in the tops at the 58-day stage.